INSTALLATION INSTRUCTIONS
MPD Direct-Vent
Gas Fireplaces
MODELS
MILLIVOLT:
ELECTRONIC:
P/N 850014 Rev. V 08/2011
MPDT-3328CNM-B MPD-4035CNM-B
MPDT-3328CPM-B MPD-4035CPM-B
MPDR-3328CNM-B MPD-4540CNM-B
MPDR-3328CPM-B MPD-4540CPM-B
MPD-3530CNM-B
MPDT-3328CNE-B
MPDT-3328CPE-B
MPDR-3328CNE-B MPD-4540CNE-B
MPDR-3328CPE-B
MPD-3530CNE-B
MPD-3530CPE-B
MPD-4035CNE-B
MPD-4035CPE-B
This manual is one of a set of two supporting this product.
Refer to P/N 875014M for Care and Operation Instructions.
Ce manuel est disponible en francais, simplement
en faire la demande. Numéro de la pièce 850014CF.
MPD-4540CPE-B
MPD-3530CPM-B
Portland
US
INSTALLER: Leave this manual with the appliance.
CONSUMER: Retain this manual for future reference.
OTL Report No. 116-F-13-4
INSTALLATEUR : Laissez cette notice avec l’appareil.
CONSOMMATEUR : Conservez cette notice pour
consultation ultérieure.
Please read and understand these instructions
before starting installation.
This appliance may be installed in an aftermarket permanently located, manufactured home (USA only) or mobile
home, where not prohibited by local codes. This appliance is only for use with the type of gas indicated on the rating
plate. This appliance is not convertible for use with other gases, unless a certified kit is used.
/
/
WARNING AVERTISSEMENT AVISO
• HOT GLASS WILL CAUSE
BURNS.
• DO NOT TOUCH GLASS
UNTIL COOLED.
• UNE SURFACE VITRÉE CHAUDE
PEUT CAUSER DES BRÛLURES.
• LAISSER REFROIDIR LA SURFACE
VITRÉE AVANT D'Y TOUCHER.
• EL VIDRIO CALIENTE
CAUSARÁ QUEMADURAS.
• USTED DEBE NUNCA
TOCAR EL VIDRIO CALIENTE.
• NEVER ALLOW CHILDREN
TO TOUCH GLASS.
• NE PERMETTEZ JAMAIS À UN ENFANT • LOS NIÑOS DEBEN NUNCA
DE TOUCHER LA SURFACE VITRÉE.
TOCAR EL VIDRIO.
WARNING: If the information in these instructions
is not followed exactly, a fire or explosion may
result, causing property damage, personal injury,
or death.
AVERTISSEMENT : Assurez-vous de bien suivre les
instructions données dans cette notice pour réduire au
minimum le risque d’incindie ou d’explosion ou pour
éviter tout dommage matériel, toute blessure ou la mort.
- Do not store or use gasoline or other flammable
vapors and liquids in the vicinity of this or any other
appliance.
- Ne pas entreposer ni utilizer d’essence ni d’autres vapeurs
ou liquides inflammables dans le voisinage de cet appareil
ou de tout autre appareil.
- WHAT TO DO IF YOU SMELL GAS:
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use any
phone in your building.
• Immediately call your gas supplier from a
neighbor’s phone. Follow the gas supplier’s
instructions.
• If you cannot reach your gas supplier, call the fire
department.
- Installation and service must be performed by a
qualified installer, service agency or the gas supplier.
- QUE FAIRE SI VOUS SENTEZ UNE ODEUR DE GAZ :
• Ne pas tenter d’allumer d’appareil.
• Ne touchez à aucan interrupteur. Ne pas vous servir des
téléphones se trouvant dans le bâtiment où vous trouvez.
• Appelez immédiatement votre fournisseur de gaz depuis
un voisin. Suivez les instructions du fournisseur.
• Si vous ne pouvez rejoindre le fournisseur de gaz,
appelez le service des incindies.
- L’installation et l’entretien doivent être assurés par un
installateur ou un service d’entretien qualifié ou par le
fournisseur de gaz.
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
The appliance, when installed, must be electri-
Note: Installation and repair should be done
by a qualified service person. The appliance
should be inspected before use and at least
annually by a professional service person.
More frequent cleaning may be required due
to excessive lint from carpeting, bedding
material,etcetera.Itisimperativethatcontrol
compartments, burners and circulating air
passageways of the appliance be kept clean.
Remarque: L’installation et la réparation
devraitêtreconfiéesàuntechnicienquali-
fié. L’appareil devrait faire l’objet d’une
inspectionparuntechnicienprofessionnel
avant d’être utilisé et au moins une fois
l’an par la suite. des nettoyages plus
fréquents peuvent être nécessaires si les
tapis, la literie, et cetera produisent une
quantité importante de pous-sière. Il est
essentiel que les compartiments abritant
les commandes, les brûleurs et les con-
duits de circulation d’air de l’appareil
soient tenus propres.
cally grounded and wired in accordance with
local codes or, in the absence of local codes,
with the National Electrical Code, ANSI/NFPA
70 - latest edition, or the Canadian Electrical
Code, CSA C22.1 - latest edition.
WARNING
Improper installation, adjust-
ment, alteration, service or
maintenance can cause injury
or property damage. Refer to
this manual. For assistance or
additional information consult
a qualified installer, service
agency or the gas supplier.
Provide adequate clearances around air open-
ings and adequate accessibility clearance for
service and proper operation. Never obstruct
the front or back openings of the appliance.
These appliances are designed to operate on
natural or propane gas only. The use of other
fuels or combination of fuels will degrade
the performance of this system and may be
dangerous.
WARNING
Failure to comply with these
installationinstructionswillresult
in an improperly installed and
operating appliance, voiding its
warranty. Anychangetothisappli-
anceand/oritsoperatingcontrols
is dangerous.
These fireplaces are designed as supplemental
heaters. Therefore, it is advisable to have an
alternate primary heat source when installed
in a dwelling.
do not use these appliances if any part
has been under water. Immediately call a
qualified, professional service technician
to inspect the appliance and to replace
any parts of the control system and any
gas control which have been under water.
Ne pas utiliser cet appareil s’il a été
plongé, même partiellement, dans
l’eau. Appeler un technicien qualifié
pour inspecter l’appareil et remplacer
toute partie du système de commande
et toute commande qui a été plongée
dans l’eau.
Millivolt Models - The millivolt appliances are
manually controlled and feature a spark igniter
(piezo) that allows the appliance's pilot gas to
be lit without the use of matches or batteries.
This system provides continued service in the
event of a power outage.
WARNING
Clothing or other flammable
material should not be placed
on or near the appliance.
Millivolt models come standard with a manually
modulatedgasvalve;flameappearanceandheat
outputcanbecontrolledatthegasvalve.TheBTU
Input for these appliances is shown in Table 1.
AVERTISSEMENT
IMPROPER INSTALLATION OR USE OF THIS
APPLIANCE CAN CAUSE SERIOUS INjURY OR
dEATH FROM FIRE, BURNS, EXPLOSION OR
CARBON MONOXIdE POISONING.
Electronic Models - Electronic models have a
fixed rate gas valve. Input of electronic models
is shown in Table 1.
On ne devrait pas placer de
vêtements ni d’autres matières
inflammables sur l’appareil ni à
proximité.
Onlytrimkit(s)suppliedbythemanufacturer
shall be used in the installation of this ap-
pliance.
Input (BTU/HR) Gas Valves (all models)
Input Rate (BTU / HR)
Models
WARNING
Seules les trousses de garniture fournies
parlefabricantdoiventêtreutiliséespour
l’installation de cet appareil.
Nat. Gas
Prop. Gas
Any safety screen or guard
removed for servicing the appli-
ance must be replaced prior to
operating the appliance.
MPdT/R-3328
(Millivolt)
17,500 high
11,700 low
17,500 high
14,000 low
These appliances comply with National
Safety Standards and are tested and listed
by OMNI-Test Laboratories, Inc. (Report No.
116-F-13-4) to ANSI Z21.88 (in Canada, CSA-
2.33), and CAN/CGA-2.17-M91 in both USA
and Canada, as vented gas fireplace heaters.
MPd-3530
(Millivolt)
20,000 high
12,800 low
20,000 high
15,200 low
MPd-4035
(Millivolt)
27,000 high
18,500 low
27,000 high
21,500 low
AVERTISSEMENT
MPd-4540
(Millivolt)
29,000 high
20,500 low
29,000 high
22,500 low
Tout écran ou protecteur retiré
pour permettre l’entretien de
l’appareil doit être remis en
place avant de mettre l’appareil
en marche.
Both millivolt and electronic versions of
these appliances are listed by OMNI-Test
Laboratories for installation in bedrooms
and Manufactured Homes.
MPdT/R-3328
17,500
20,000
27,000
29,000
17,500
20,000
27,000
29,000
(Electronic)
MPd3530
(Electronic)
Misc. Codes / Standards
MPd4035
(Electronic)
TheInstallationmustconformtolocalcodesor,
in the absence of local codes, with the National
Fuel Gas Code, ANSI Z223.1/NFPA 54 - latest
edition(InCanada,thecurrentCAN/CSA-B149.1
installation code).
MPd4540
(Electronic)
Table 1
3
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Gas Pressure - All Models
For elevations above 4500 feet, contact your
gas supplier or qualified service technician.
Electronic
Gas Control
Valve
Tables 2 and 3 show the appliances' inlet and
manifold gas pressure requirements:
deration - At higher elevations, the amount
of BTU fuel value delivered must be reduced
by either using gas that has been derated by
the gas company or by changing the burner
orifice to a smaller size as regulated by the
local authorities having jurisdiction and by the
(USA) National Fuel Gas Code NFPA 54/ANSI
Z223.1 - latest edition or, in Canada, the CAN/
CSA-B149.1 codes - latest edition.
Inlet
Pressure
Port
Inlet Gas Supply Pressure
(all models)
Fuel #
Minimum
Maximum
4.5" WC
(1.12 kPa)
10.5" WC
(2.61 kPa)
Natural Gas
ON/OFF Switch
Manifold Pressure Port
11.0" WC
(2.74 kPa)
13.0" WC
(3.23 kPa)
Propane
Figure 2: Honeywell Electronic Gas Valve
Installtheapplianceaccordingtotheregulations
of the local authorities having jurisdiction and,
in the USA, the National Fuel Gas Code NFPA
54 / ANSI Z223.1 - latest edition or, in Canada,
the CAN/CSA-B149.1 - latest edition.
Table 2
REQUIREMENTS FOR THE COMMON-
WEALTH OF MASSACHUSETTS
Manifold Gas Supply Pressure
(all models)
These fireplaces areapproved for installationin
the US state of Massachusetts if the following
additional requirements are met:
• Install this appliance in accordance with
Massachusetts Rules and Regulations 248
C.M.R.
• Installation and repair must be done by a
plumber or gas fitter licensed in the Com-
monwealth of Massachusetts.
Fuel #
Low
High
Flame breadth, height and width will dimenish
4% for every 1,000 feet of altitude.
Natural (Lo) 1.6" WC
Gas
(Hi) 3.5" WC
(0.87 kPa)
(0.40 kPa)
(Lo) 6.3" WC (Hi) 10.0" WC
(1.57 kPa) (2.49 kPa)
Burner Orifice Sizes
Elevation 0-4500 feet ( 0-1372 meters)
Propane
Table 3
Model
Series
Nat.Gas
drill size (inches)
Propane
drill size (inches)
• The flexible gas line connector used shall
not exceed 36 inches (92 centimeters) in
length.
• The individual manual shut-off must be a
T-handle type valve.
Test gauge connections are provided on the
front of the millivolt and electronic gas control
valve (identified IN for the inlet and OUT for the
manifold side). The control valves have a 3/8"
(10mm) NPT thread inlet and outlet side of the
valve (refer to Figures 1 and 2).
#45 (0.0820")*
39L66•
0.048 inch
99K78•
MPdT-3328
MPdR-3328
#44 (0.0860")*
#55 (0.0520")*
19L52•
MPd-3530
60j80•
#37 (0.1040")*
24M10•
0.063 inch
21L01•
MPd-4035
Massachusetts Horizontal Vent Requirements
#36 (0.1065")*
18L40•
#52 (0.0635")*
37G00•
MPd-4540
Propane tanks are at pressures that will cause
damage to valve components. Verify that the
tanks have step down regulators to reduce the
pressure to safe levels.
IntheCommonwealthofMassachusetts,hori-
zontal terminations installed less than seven
(7) feet above the finished grade must comply
with the following additional requirements:
• A hard wired carbon monoxide detector
with an alarm and battery back-up must be
installed on the floor level where the gas
fireplace is installed. The carbon monoxide
detector must comply with NFPA 720, be
ANSI/UL 2034 listed and be ISA certified.
• A metal or plastic identification plate must
be permanently mounted to the exterior of
thebuildingataminimumheightofeight(8)
feet above grade and be directly in line with
the horizontal termination. The sign must
read, in print size no less than one-half (1/2)
inch in size, GAS VENT DIRECTLY BELOW.
KEEP CLEAR OF ALL OBSTRUCTIONS.
* Standard size installed at factory
• Part /Cat. Number
Table 4
Gas Valve diagrams
These appliances must be isolated from the
gas supply piping system (by closing their
individual manual shut-off valve) during any
pressure testing of the gas supply piping
system at test pressures equal to or less
than 1/2 psig (3.5 kPa).
See Figure 1 for Millivolt models and Figure 2
For Electronic Models.
Pilot Adjustment
Screw
Main Gas Control Knob
OFF/PILOT/ON
Theseappliancesandtheirindividualshut-off
valves must be disconnected from the gas
supply piping system during any pressure
testing of that system at pressures greater
than 1/2 psig (3.5 kPa).
T
L
I
P
N
O
T
W O
L
O
L I
P
F
O
H
I
IN OUT
These appliances must not be connected to a
chimney or flue serving a separate solid fuel
burning appliance.
Manifold Pressure Tap
NEW YORK CITY, NEW YORK (MEA)
HI/LO Variable
Flame Height
Adjustment
Inlet Pressure Tap
Orifice Sizes - Sea Level to High Altitude
(All Models)
Installation of these fireplaces are approved
for installation in New York City in the US state
of New York.
Figure 1: SIT Millivolt Gas Valve
These appliances are tested and approved for
installation at elevations of 0-4500 feet (0-1372
meters)abovesealevelusingthestandardburner
orifice sizes (marked with an "*" in Table 4 ).
4
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
COLd CLIMATE INSULATION
For cold climate installations, seal all cracks
around your appliance with noncombustible
material and wherever cold air could enter
the room. It is especially important to insulate
outside chase cavity between studs and under
floor on which appliance rests, if floor is above
ground level. Gas line holes and other open-
ings should be caulked or stuffed with unfaced
fiberglass insulation.
APPLICATION
TOP VENT
If the fireplace is being installed on a cement
slab in cold climates, a sheet of plywood or
otherraisedplatformcanbeplacedunderneath
to prevent conduction of cold transferring to
the fireplace and into the room. It also helps to
sheetrockinsidesurfacesandtapeformaximum
air tightness and caulk firestops.
RECESSED
INSTALLATION
TOP VENT
APPLICATION
MANUFACTUREd HOME
REQUIREMENTS
Thisappliancemaybeinstalledinanaftermarket
permanently located, manufactured home and
must be installed in accordance with the manu-
facturer's instructions and the Manufactured
Home Construction and Safety Standard, Title
24 CFR, Part 3280, in the United States, or the
StandardforInstallationinMobileHomes,CAN/
CSA Z240 MH Series, in Canada.
VERTICAL VENT
HORIZONTAL VENT
(Rear Vent Application) (Rear Vent Application without a chase)
Cet appareil peut être installé cómme
du matéri-el d'origine dans une maison
préfabriquée (É.U. seulement) ou mobile
et doit être installé selon les instructions
du fabricant et conformément à la norme
Manufactured Home Constructions and
Safety, Title 24 CFR, Part 3200 aux Unis
ou à la norme Can/CSA-Z240 Série MM,
Maisons mobiles au Canada.
VERTICAL VENT
(Top Vent Application)
HORIZONTAL VENT
HORIZONTAL VENT
(Rear Vent Application with a chase) (Top Vent Application)
Figure 3: Typical Locations
Thisapplianceisonlyforusewiththetypeofgas
indicated on the rating plate. This appliance is
notconvertibleforusewithothergases, unless
a certified kit is used.
Be aware that this is a heat producing ap-
pliance. Objects placed above the unit are
exposed to elevated temperatures.
LOCATION
In selecting the location, the aesthetic and
functional use of the appliance are primary
concerns. However, vent system routing to
the exterior and access to the fuel supply are
also important.
Cet appareil doit être utilisé uniquement
avec le type de gaz indiqué sur la plaque
signalétique. Cet appareil ne peut être
converti à d'autres gaz, sauf si une trousse
de conversion est utilisée.
do not insulate the space between the appli-
ance and the area above it (see Figure 8 ).
Theminimumheightfromthebaseoftheappli-
ance to the underside of combustible materials
used to construct a utility shelf in this fashion
is shown in Figure 8.
due to high temperatures, the appliance
should be located out of traffic and away from
furniture and draperies (Figure 3).
CAUTION: Ensure that the cross mem-
bers are not cut or weakened during
installation. The structural integrity of
the manufactured home floor, wall, and
ceiling / roof must be maintained.
En raison des températures élevées,
l’appareil devrait être installé dans un
endroit où il y a peu de circulation et loin
du mobilier et des tentures (Figure 3).
The appliance should be mounted on a fully
supported base extending the full width and
depth of the unit. The appliance may be located
onornearconventionalconstructionmaterials.
However, if installed on combustible materials,
such as carpeting, vinyl tile, etc., a metal or
woodbarriercoveringtheentirebottomsurface
must be used.
The location should also be free of electrical,
plumbing or other heating/air conditioning
ducting.
CAUTION: This appliance must be ground-
ed to the chassis of the manufactured
home in accordance with local codes or
in the absence of local codes, with the
National Electrical Code ANSI / NFPA 70
- latest edition or the Canadian Electrical
Code CSA C22.1 - latest edition.
These direct-vent appliances are uniquely
suited for installations requiring a utility shelf
positioned directly above the fireplace. Util-
ity shelves like these are commonly used for
locat-ing television sets and decorative plants.
5
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
VenT TerminaTion ClearanCes
Vertical Vent Termination Clearances
The vent / air intake termination clearances
above the high side of an angled roof are as
shown in the following chart:
These instructions should be used as a
guideline and do not supersede local codes
in any way. install venting according to local
codes,theseinstructions,thecurrentnational
Fuel Gas Code (ansi-Z223.1) in the Usa or
the current standards of Can/Csa-B149.1
in Canada.
TERMINATION HEIGHTS FOR VENTS ABOVE
FLAT OR SLOPED ROOFS
Horizontal Overhang
Termination Heights For Vents
above Flat or sloped roofs
ref. nFPa 54 / ansi Z223.1
2 FT
MIN.
Vertical
Wall
2 FT MIN.
Lowest
Discharge
Opening
roof Pitch
*H (ft)
1.0
*H (m)
0.3
Vent
Termination
Flat to 6/12
Vertical Vent Termination Clearances
6/12 to 7/12
1.25
1.5
0.38
0.46
0.61
0.76
0.99
1.22
1.52
1.83
2.13
2.29
2.44
H*
Storm Collar
Flashing
X
7/12 to 8/12
Terminatemultipleventterminationsaccordingto
the installation codes listed above and Figures
4 and 5.
12
8/12 to 9/12
2.0
Roof Pitch is X/12
9/12 to 10/12
10/12 to 11/12
11/12 to 12/12
12/12 to 14/12
14/12 to 16/12
16/12 to 18/12
18/12 to 20/12
20/12 to 21/12
2.5
1 inch (25.4 mm) Minimum
Clearance to Combustibles
3.25
4.0
Concentric
Vent Pipe
*H = MINIMUM HEIGHT FROM ROOF TO
LOWEST DISCHARGE OPENING OF VENT
12”
(305mm)
minimum
5.0
6.0
7.0
7.5
8.0
Figure 5
Horizontal Vent Termination Clearances
Figure 4 - Multiple Terminations
The horizontal vent termination must have a minimum of 6" (152 mm) clearance to any overhead
combustible projection of 2-1/2" (64 mm) or less (see Figure 6). For projections exceeding 2-1/2"
(64 mm), see Figure 6. For additional vent location restrictions refer to Figure 7 on Page 7.
Horizontal Vent Termination Clearances
Combustible Projection
2-1/2 inches or less in length
All horizontal terminations
may be located as close as
6” (152mm) to any
(non-combustible and
combustible) exterior
sidewall. This distance
may be decreased to 2”
(51mm) for non-
combustible exterior
sidewalls only, if the
SV4.5HT-2 termination
is used.
Combustible Projection greater
than 2-1/2 inches in length
Ventilated
Soffit
Unventilated
Soffit
6"
(152 mm)
18"
12"
(457 mm)
(305 mm)
Termination Kit
Side Elevation View
Termination Kit
Note - See Figure 37 on Page 20 for the exterior wall recess
allowances of the square horizontal termination.
Figure 6
6
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
EXTERIOR HORIZONTAL VENT TERMINATION CLEARANCE REQUIREMENTS
NOTE: Local Codes Or Regulations
May Require Different Clearances.
* See Item D in the Text Below.
Exterior Wall
P
V
N
N
NOTE: Location Of The Vent Termination
Must Not Interfere With Access To The
Electrical Service.
Inside
Corner Detail
O
*18”
V
G
V
Q
Horizontal
Termination
6”
Inside Corner
Detail D
Ventilated Soffit
A
= 9” in U.S.
= 12” in Canada
A
H
3 ft.
X
B
B
B
D
E
C
C
A
A
V
V
V
Fixed
Operable
Window
L
V
Closed
3 ft.
Window
V
F
J
M
V
C
B
B
C
V
I
A
X
= Air Supply Inlet
V
= Vent Termination
= Area where Termination is not Permitted
Canadian Installation*
US Installation**
12 inches (30cm)**
6 inches (15cm) for appliances
< 10,000 Btuh (3kW), 9 inches (23cm)
for appliances > 10,000 Btuh (3kW) and
< 50,000 Btuh (15kW), 12 inches (30cm)
for appliances > 50,000 Btuh (15kW)**
A = Clearance above grade, veranda, porch, deck, or balcony. 12 inches (30cm)*
B = Clearance to window or door that may be opened.
6 inches (15cm) for appliances
< 10,000 Btuh (3kW), 12 inches (30cm)
for appliances > 10,000 Btuh (3kW)
C = Clearance to permanently closed window
12 inches (305mm) recommended to
prevent window condensation
9 inches (229mm) recommended to
prevent window condensation
D = Vertical clearance to ventilated soffit located above the
18 inches (458mm)
18 inches (458mm)
termination within a horizontal distance of 18 inches (458mm)
E = Clearance to unventilated soffit
F = Clearance to outside corner
G = Clearance to inside corner
12 inches (305mm)
12 inches (305mm)
5 inches (12.7cm) minimum
5 inches (12.7cm) minimum
2 inches (5.08cm) minimum - SV4.5HT-2• 2 inches (5.08cm) minimum - SV4.5HT-2•
6 inches (15.2cm) minimum - SV4.5HTSS 6 inches (15.2cm) minimum - SV4.5HTSS
H = Clearance to each inside of center line extended above
meter/regulator assembly
I = Clearance to service regulator vent outlet
3 feet (91cm) within a height of 15 feet
above the meter/regulator assembly*
3 feet (91cm)*
3 feet (91cm) within a height of 15 feet
above the meter/regulator assembly**
3 feet (91cm)**
J = Clearance to nonmechanical air supply inlet to building or 6 inches (15cm) for appliances
6 inches (15cm) for appliances
the combustion air inlet to any other appliance
< 10,000 Btuh (3kW), 12 inches (30cm)
for appliances > 10,000 Btuh (3kW)
< 10,000 Btuh (3kW), 9 inches (23cm)
for appliances > 10,000 Btuh (3kW) and
< 50,000 Btuh (15kW), 12 inches (30cm)
for appliances > 50,000 Btuh (15kW)**
K = Clearance to a mechanical air supply inlet
6 feet (1.83m)*
3 feet (91cm) above if within 10 feet (3m)
horizontally**
L = Clearance above paved sidewalk or paved diveway located 7 feet (2.13m)‡
7 feet (2.13m)‡
on public property
M = Clearance under veranda, porch, deck or balcony
12 inches (30cm)*‡
6 feet (1.83m)*
12 inches (30cm)‡
6 feet (1.83m)**
N = Depth of Alcove (Maximum)
O = Clearance to Termination (Alcove)
P = Width of Alcove (Minimum)
6 inches (15.2mm)*
3 feet (91cm)*
6 inches (15.2mm)**
3 feet (91cm)*
Q = Clearance to Combustible Above (Alcove)
18 inches (457mm)*
18 inches (457mm)**
* In accordance with the current CSA-B149.1 National Gas And Propane Installation Code.
** In accordance with the curent ANSI SZ223.1/NFPA 54 National Fuel Gas Codes.
‡ A vent shall not terminate directly above a sidewalk or paved driveway which is located between two single family dwellings and serves both
dwellings.
*‡ Only permitted if veranda, porch, deck or balcony is fully open on a minimum 2 sides beneath the floor.
•2 inch Clearance to Non-Combustibles for SV4.5HT-2 Only.
Figure 7
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
7
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
MINIMUM CLEARANCES TO COMBUSTIBLES
MINIMUM CLEARANCES* Inches (millimeters)
Back
1/2 in. (13)
0 (0) from Spacers Or dimples
Appliance And Vent Clearances
The appliance is approved with zero clearance to combustible materials
on all sides (as detailed in Table 5), with the following exception: When
the unit is installed with one side flush with a wall, the wall on the
other side of the unit must not extend beyond the front edge of the
unit. In addition, when the unit is recessed, the side walls surrounding
the unit must not extend beyond the front edge of the unit (see Figure 3).
Sides
1/2 in. (13)
0 (0) from Spacers Or dimples **
Top Spacers
0 (0)
Floor
FromBottomofUnitTo Ceiling
Vent
0 (0)
64 (1626)
HearthExtension-Ahearthextensionisnotrequiredwiththisappliance.
If a hearth extension is used, do not block the lower control compartment
door. Any hearth extension used is for appearance only and does not
have to conform to standard hearth extension installation requirements.
3 (76) Top* / 1 (25.4)Sides & Bottom
SERVICE CLEARANCES Feet (meters)
Front
3 feet (0.9 meters)
Table 5
Shelf Height - To provide for the lowest possible shelf surface, use the
alternate rear vent outlet, the venting attached to the top vent should be
routedinawaytominimizeobstructionstothespaceabovetheappliance.
do not insulate the space between the appliance and the area above
it (see Figure 8). The minimum height from the base of the appliance to
the underside of combustible materials used to construct a utility shelf in
this fashion is shown in Figure 8.
*Note: 3 in. (75 mm) above any horizontal/inclined vent component.
**Note: See Page 10, Step 1 for clearance requirements to the nailing
flange located at each side of the unit and any screw heads adjacent to it.
The appliance should be mounted on a fully supported base extending
the full width and depth of the unit. The appliance may be located on
or near conventional construction materials. However, if installed on
combustible materials, such as carpeting, vinyl tile, etc., a metal or wood
barrier covering the entire bottom surface must be used.
Combustible Shelf Height - Inches (millimeters)
Models
Top Vent - With One 90 degree Elbow
Rear Vent - Straight Out The Back
Secure Vent
44-1/2 (1130)
46-1/2 (1181)
51-1/2 (1308)
Secure Flex
46-1/4 (1175)
48-1/4 (1226)
53-1/4 (1353)
Secure Vent
33-1/4 (845)
35-1/4 (895)
40-1/4 (1022)
Secure Flex
33-1/4 (845)
35-1/4 (895)
40-1/4 (1022)
MPdT-3328
MPdR-3328
MPd-3530
MPd-4035
MPd-4540
Do not insulate the
space between the
appliance and the
area above it.
Do not insulate the
space between the
appliance and the
area above it.
Shelf Height
(see table)
Shelf Height
(see table)
Shelf Above Fireplace With Top Venting
Shelf Above Fireplace With Rear Venting
Figure 8: Shelf Height Minimum Clearances
8
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Wall Finishes / Surrounds / Mantels
Note: Combustible wall finish materials and/or surround materials must not be allowed to encroach the area defined by the appliance front face (black
sheet metal). Never allow combustible materials to be positioned in front of or overlapping the appliance face (see Figures 65 and 66 on Page 34 ).
Non-combustible materials, such as surrounds and other appliance trim, may be installed on the appliance face with these exceptions: they must not
cover any portion of the removable glass panel or control compartment.
Vertical installation clearances to combustible mantels vary according to the depth of the mantel. SeeFigure 9. Mantels constructed of non-combustible
materials may be installed at any height above the appliance opening; however, do not allow anything to hang below the fireplace hood.
MANTEL CLEARANCES
Combustible Materials
Allowed In Shaded
Area “Safe Zone”
Inches (mm)
Top View Of
Fireplace
12 (305) MANTEL
12"
10 (254) MANTEL
8 (203) MANTEL
6 (152) MANTEL
4 (102) MANTEL
2 (51) MANTEL
5"
45°
14
(356)
17"
12
(305)
Min. Distance
10
(254)
To Protected
Perpendicular
Side Wall
TOP OF
APPLIANCE
8
8-1/4"
(203)
6
(152)
4
Side
Wall
Side
Wall
(102)
Min. Distance To
Unprotected
Perpendicular Side Wall
14"
NOTE - Hood shown as positioned in louvered
front model. The hood position in the flush
faced front model is lower than shown.
Combustible materials may project beyond one side of the fireplace
opening as long as they are kept within the shaded areas illustrated here.
Figure 9: Minimum Mantel Clearances
Figure 10: Minimum Distance to Side Wall
WARNING
Failure to position the parts in accordance with these
diagrams or failure to use only parts specifically
approved with this appliance may result in property
damage or personal injury.
AVERTISSEMENT
Risque de dommages ou de blessures si les pièces
ne sont pas installées conformément à ces schémas
et ou si des pièces autres que celles spécifiquement
approuvées avec cet appareil sont utilisées.
9
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
dETAILEd INSTALLATION STEPS
PRE-INSTALLATION STEPS
TYPICAL INSTALLATION SEQUENCE
The typical sequence of installation is outlined
below; however, each installation is unique and
may result in variations to the steps described.
Step 1. FRAMING
The appliance is shipped with all gas controls
and components installed and pre-wired.
Frame the appliance as illustrated in Figures
13 and 14 on Pages 10 and 11 (Figure 14
applies to corner framing installations only).
All framing details must allow for a minimum
clearance to combustible framing members as
shown in Table 5 on Page 8.
Before installing the appliance, follow these
steps:
See the pages referenced in the following steps
for detailed procedures.
1. Remove the shipping carton.
Step 1. FRAMING (Page 10): Construct the
appliance framing. Position the appliance within
the framing and secure with nailing brackets.
2. Remove the shipping pad, exposing the front
glass door.
Iftheapplianceistobeelevatedabovefloorlevel,
asolidcontinuousplatformmustbeconstructed
below the appliance.
3. Open the two latches securing the glass
door (under the firebox floor). Remove the
door by tilting it outward at the bottom and
lifting it up. Set the door aside, taking care
to protect it from inadvertent damage. See
Removing Glass Panels on Page 32.
IMPORTANT! Bend up the appropriate header
spacing standoffs for the drywall/finish mate-
rial thickness to be used (see Figure 60, page
32). Bend up the outer pair for 1/2" materials
and the inner pair for 5/8" materials.
Headers may be in direct contact with the appli-
ance top standoff spacers when they are bent
up vertically, maintaining the 3" clearance to
the fireplace top, but must not be supported
by them or notched to fit around them. All
construction above the appliance must be
self-supporting. DO NOT use the appliance
for structural support.
Bend out the appropriate nailing flanges for
the drywall/finish material to be used. Nailing
flanges are provided for flush framing, 1/2-inch
and 5/8-inch framing depths (see Figure 12).
4. See Figure 11. Remove the top louvered
panel and locate the pressure relief plates.
Lift the pressure relief plates, and remove the
cardboard from beneath each plate (taking
care not to damage the white gasket).
Step 2. ROUTING GAS LINE (Page 12): Route
gas supply line to appliance location.
Securethefireplacetothesideframingmembers
using the unit’s nailing flanges — one top and
bottom on each side of the fireplace front. See
Figure 12. Use 8d nails or their equivalent.
5. Remove the log set from the firebox. Handle
logs carefully to prevent breakage.
Step 3. PREPARING APPLIANCE VENT COLLAR
(MPD-3530/4035/4540 models with combined
top/rear vent) (Page 13).
6. Remove the embers and volcanic stone from
the control compartment.
Step 4. INSTALLING VENT SYSTEM (Page 13):
Install the vent system and exterior termination.
IMPORTANT!
Bend up the appropriate header spacing top
standoffs before installing the fireplace.
Step 5. FIELd WIRING (Page 25).
a. Millivolt Appliances – Install the operat-
ing control switch (not factory provided). If
installing the optional forced air circulating
blower, bring in electrical service line.
Header Spacing Top Standoffs
(two pairs on front edge of firebox top)
Pressure Relief
Plates
Lift up outer pair for
1/2" finish materials. Lift up inner pair for
5/8" finish materials.
b. Electronic Appliances – Field wire and
install operating control switch.
Step 6. WIRING - OPTIONAL FORCEd AIR
BLOWER KIT (Page 26).
VE
MO
Rd
RE
FO
BE
RE
CA
VE
MO
Rd
RE
FO
BE
RE
CA
d
AR
BO
d
AR
BO
ING
US
ING
US
Step 7. CONNECTING GAS LINE (Page 26):
Make connection to gas supply.
Unit Nailing Flange
(No clearance to
combustible framing
is required.)
Step 8. VERIFYING APPLIANCE OPERATION
(Page 27).
Step 9. INSTALL LOGS, VOLCANIC STONE,
ANd GLOWING EMBERS (Page 28).
Remove cardboard before using appliance.
Take care not to damage white gasket.
Side
Framing
Step 10. INSTALLING GLASS dOOR ASSEM-
BLY (Page 32).
Figure 11
Unit Secured to Framing
by Nailing Flange
Left Side Front Corner of Fireplace Shown
(Right side requirements are the same)
Step 11. BURNER AdjUSTMENTS (Page 32):
Adjust burner to ensure proper flame appear-
ance.
NOTE: The nailing flanges, combustible
members, and screw heads in areas directly
adjacent to the nailing flanges are EXEMPT
from the 1/2" clearance to combustible
requirements for the firebox outer wrapper.
Step 12. HOOd INSTALLATION (Page 34).
Step 13. ATTACHING SAFETY-IN-OPERATION
WARNINGS (Page 35).
Combustible framing may be in direct contact
with the nailing flanges and may be located
closer than 1/2" from screw heads and the
firebox wrapper in areas adjacent to the
nailing flanges.
Frame the opening to the exact dimensions
specified in the framing details in this manual.
Figure 12
10
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
FIREPLACE ANd FRAMING SPECIFICATIONS
Framing
VENT FRAMING:
TOP VENT WITH ONE
90° ELBOW
Framing should be
constructed of 2x4
or larger lumber.
10-1/2
(267)
Model No.
A
B
C
D
E
in.
33 1/4 33 1/4
845 845
33 1/4 33 1/4
845 845
-----
-----
19 5/8
498
37 3/4 12 7/8
MPDT-3328
VENT FRAMING:
REAR VENT WITH
NO ELBOWS
mm
in.
959
-----
-----
327
12 7/8
327
16
MPDR-3328
MPD-3530
MPD-4035
MPD-4540
7
mm
in.
(178)
5-1/8
(130)
12-1/8
(308)
35 1/4 35 1/4 21 11/16 39 3/4
895 895 551 1010
40 1/4 40 1/4 26 11/16 44 3/4
1022 678 1137
45 1/4 40 1/4 26 11/16 44 3/4
mm
in.
406
16
mm 1022
in.
mm 1149
406
16
7
(178)
5-1/8
(130)
12-1/8
(308)
D
1022
678
1137
406
B
Notes
diagrams, illustrations and photographs are not to scale. Consult installation
instructions. Product designs, materials, dimensions, specifications, colors,
and prices are subject to change or discontinuance without notice.
C
E
1/2 A
Vent Size
Inches (mm)
A
Coaxial dV Vent Size 4-1/2" Inner; 7-1/2" Outer
Dimension “E” is the required framing depth when the
finish material (drywall) thickness is 1/2 in. (13mm).
Efficiencies %
Viewable Glass Size
Natural Gas
Propane
27-1/2" Wide
17" High
Fireplace
Model
33" Model
35" Model
40" Model
45" Model
Vertical Venting through the Ceiling
EnerGuide
(P4)
EnerGuide
AFUE
AFUE
(P4)
Frame ceiling opening: Use a plumb line from the ceiling
above the appliance to locate center of the vertical run. Cut
and/or frame an opening, 10-1/2" x 10-1/2" (267 mm x 267 mm)
inside dimensions, about this center mark (see Figure 18).
29-1/2" Wide
18-7/8" High
MPdT-3328
MPdR-3328
MPd-3530
MPd-4035
MPd-4540
62
61
62
67
67
45
64
64
60
67
67
49
53
55
34-1/2" Wide
24" High
53
55
39-1/2" Wide
24" High
59
60
59
59
Top View
Front View
Right Side View
NOTE: Eyebrow hood
shown as positioned
in louvered front model.
3 (76)
(Louvered Front Model Shown)
E
N
Rear/Side
Framing
Spacers
G
H
1/2 (13)
Concentric Flue:
Flue 4-1/2" (114 mm);
Combustion Air
See Note [2].
Gas Inlet (either
side and bottom)
Header
Spacing
Top
7-1/2" (190 mm).
6 (152)
See Notes [1] and [2].
Optional Electrical Inlet
Knockout requiring a
Field-Provided Junction
Box (either side)
Standoffs
A
L
F (rear vent
C
B
models only)
J
D
1-5/8 (42)
M
Electrical Inlet
2-3/4" x 2"
(70 x 51 mm)
Cover Plate
1-3/8 (35)
K
Notes:
[1]MPD models have a top and rear vent. MPDR models
have a rear vent only. MPDT models have a top vent only.
with Knockout
[2]Collars protrude one inch on MPDT-3328 and MPDR-3328 models.
Model No.
A
B
C
D
E
F
G
H
J
K
3
L
M
N
in.
33 1/8 30 1/8 17 27 1/2 33 1/8
841 765 432 699 841
19 5/8
498
21 1/2
546
10 3/4
273
6 13/16
173
8 11/32 2 2/3 13
MPDT-3328
MPDR-3328
mm
76
212
70
330
in.
mm
35 1/8 32 1/8 19 29 1/2 35 1/8 21 11/16 24 7/8 12 7/16
892 816 483 749 892 551 632 316
40 1/8 37 1/8 24 34 1/2 40 1/8 26 11/16 29 7/8 14 15/16
mm 1019 943 610 876 1019 678 759 379
in. 40 1/8 37 1/8 24 39 1/2 45 1/8 26 11/16 34 7/8 17 7/16
mm 1146 943 610 1003 1146 678 886 443
9
220
9
220
9
3
76
3
76
3
9
220
9
220
9
3
76
3
76
3
16
406
16
406
16
MPD-3530
MPD-4035 in.
MPD-4540
220
76
220
76
406
Figure 13
11
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
FIREPLACE FRAMING SPECIFICATIONS
Model No.
A
B
C
D
E
F
5
b
in. 33 1/8 48 1/2 34 5/16 17 3/16 241/4
MPDT-3328
MPDR-3328
MPD and MPDR units
mm 841 1232
872
437
616
127
F
in. 35 1/8 57 1/2 40 5/8 19 3/16 28 3/4 6 1/8
mm 892 1461 1032 487 730 156
in. 40 1/8 61 3/16 43 11/32 19 3/16 30 11/16 7 7/8
mm 1019 1554 1101 487 779 200
in. 45 1/8 66 3/8 46 15/16 19 3/16 33 3/16 9 3/4
mm 1146 1686 1192 487 843 248
7"
MPD-3530
MPD-4035
MPD-4540
MPD and MPDT units
(178 mm)
C
E
D
a
Note:
• Rear Vent Applications in Corner Installations: The horizontal vent length
a
b
(from
to ) must not exceed 28 inches (711 mm).
• MPdT-3328 ANd MPdR-3328 Models: Dimensions A through F occur when
one 45-degree elbow is connected directly to the appliance collar.
A
• MPd-3530, MPd-4035, and MPd-4540 Models: Dimensions d through F
occur when one 45-degree elbow is connected directly to the appliance collar.
B
Back wall of chase/enclosure (including any finishing materials)
Figure 14: Corner Framing with Horizontal Termination
Never use galvanized or plastic pipe. Refer to
Table 6 for proper sizing of the gas supply line,
Notes:
Step 2. ROUTING GAS LINE
• All appliances are factory-equipped with
a flexible gas line connector and 1/2 inch
shutoff valve (see Figure 50 on Pagec 25).
Route a 1/2" (13 mm) gas line to the left side
of the appliance as shown in Figure 15. Gas
lines must be routed, constructed and made
of materials that are in strict accordance with
local codes and regulations. All appliances
are factory-equipped with a flexible gas line
connector and 1/2-inch shutoff valve. (See
Step 6 on Page 25).
if black iron pipe is being used. Gas lines must
be routed, constructed and made of materials
that are in strict accordance with local codes
and regulations. We recommend that a quali-
fied individual such as a plumber or gas fitter
be hired to correctly size and route the gas
supply line to the appliance. Installing a gas
supply line from the fuel supply to the appliance
involves numerous considerations of materials,
protection, sizing, locations, controls, pressure,
sediment, and more. Certainly no one unfamil-
iar and unqualified should attempt sizing or
installing gas piping.
• SeeMassachusettsRequirementsonPage
4 foradditionalrequirementsforinstallations
in the state of Massachusetts in the USA.
• ThegassupplylineshouldNotbeconnected
to the appliance until Step 6 (Page 25).
• Apipejointcompoundratedforgasshouldbe
usedonthethreadedjoints.Ensurepropane
resistant compounds are used in propane
applications. Be very careful that the pipe
compound does not get inside the pipe.
Left Side Front
Corner of Fireplace
Framing
Pipe Coupling
(Recommended)
• It is recommended to install a sediment trap
in the supply line as close as possible to the
appliance. AppliancesusingPropane should
have a sediment trap at the base of the tank.
Schedule 40
Black Iron Pipe
Inside diameter (Inches)
6-1/2"
(152 mm)
Schedule 40 Pipe
Length (feet)
Natural
Gas
Propane
Gas
• Check with local building official for local
code requirements (i.e. are below grade
penetrations of the gas line allowed?, etc).
3"
(76 mm)
0-10
10-40
1/2
1/2
1/2
3/4
3/4
3/8
1/2
1/2
1/2
1/2
Also see Figure 13.
IMPORTANT:Ifpropaneisused,beawarethat
if tank size is too small (i.e. under 100-lbs, if
this is the only gas appliance in the dwelling.
Ref. NPFA 58), there may be loss of pressure,
resulting in insufficient fuel delivery (which
can result in sooting, severe delayed ignition
orothermalfunctions). Anydamageresulting
from an improper installation, such as this,
is not covered under the limited warranty.
40-100
Figure 15: Route Gas Line
100-150
150-200
Table 6
Proper Sizing of Gas Line
Properly size and route the gas supply line
from the supply regulator to the area where the
appliance is to be installed per requirements
outlined in the National Fuel Gas Code, NFPA
54 - latest edition (USA) or CAN/CSA-B149.1
- latest edition (Canada).
12
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Select Venting System - Horizontal or Vertical
Step 3. PREPARING APPLIANCE VENT
COLLAR (MPd-3530/4035/4540 models
with combined top/rear vent)
Use only approved vent components (see
Approved Vent Components on Page 2).
Withtheappliancesecuredinframing,determine
vent routing and identify the exterior termina-
tion location. The following sections describe
vertical (roof) and horizontal (exterior wall)
vent applications. Refer to the section relating
to your installation. A list of approved venting
components are shown on Pages 34 and 35.
These fireplaces must be vented directly
to the outside.
Each of the unit’s two vent collars are sealed
with a cover plate and a seal plate and gasket.
The cover, and seal plate and gasket must be
removedfromtheventcollarbeingused. Refer
to Figure 16 for top vent usage and Figure 17
for rear, and the following steps to prepare the
appropriate collar for use.
The vent system may not service multiple
appliances, and must never be connected to a
flue serving a solid fuel burning appliance. The
vent pipe is tested to be run inside an enclosed
wall (such as a chase). There is no requirement
for inspection openings in the enclosing wall at
any of the joints in the vent pipe.
VENT RESTRICTOR INSTALLATION
(TOP VENT)
Fromtheventcollarbeingused, removethefour
screws securing the vent seal plate and gasket.
Remove and discard the seal plate and gasket.
A vent restrictor may be needed when
vertically terminating the vent system above
the roof (when using the appliance top vent),
install vent restrictor in the top vent of the
fireplace outlet on MPD-3530/4035/4540
and MPDT-3328 series models.
Installation of Vent Restrictor
When the top vent collar is being used, from
inside the firebox, loosen the two screws in the
keyhole slots of the cover plate and remove the
remaining two cover plate securing screws.
Remove and discard the cover plate. Reinstall
and securely tighten all four screws.
A vent restrictor may be needed with this ap-
pliance, install vent restrictor (provided) in the
appliance top flue outlet as shown in Figure 18
(MPDT-3328,MPD-3530,MPD-4035andMPD-
4540) or rear flue outlet as shown in Figure 19
(MPD-3530, MPD-4035 and MPD-4540). It is
held in place by friction, only.
If needed, install the restrictor orientated as
shown, either from inside or outside the unit,
in the inner fireplace collar.
RESTRICTOR
When the rear vent collar is being used, from
inside the firebox, remove the two screws se-
curing the lintel to the rear wall of the firebox,
then remove the lintel. Remove the four cover
plate securing screws. Remove and discard
the cover plate.
Note: The vent restrictor is included in the
firebox.
ON MPD-3530/4035/4540 SERIES MODELS
(COMBINED TOP AND REAR VENT UNITS)
TOP VENT SEAL & COVER PLATE REMOVAL
WHEN USING THE TOP VENT
INNER
FIREPLACE
COLLAR
APPLIANCE TOP
VENT OUTLET
Reinstall and securely tighten all four cover
plate screws. Re-secure the lintel to the rear
wall of the firebox.
VENT SEAL PLATE
(OUTSIDE UNIT)
Figure 18
GASKET
SECURING
SCREWS
CABINET TOP
WARNING
VENT RESTRICTOR INSTALLATION
(REAR VENT)
TOP VENT
Failure to reinstall and securely
tightencoverplatescrewscould
resultinleakageofflueproducts
intothelivingspace. Ventcover
plate and vent seal cap must
remain securely in stalled on
unused vent collar. Failure to
do so could result in leakage of
flue products into living space.
A vent restrictor may be needed when
horzontally terminating the vent system from
the rear of the appliance (when using the
appliance rear vent), install vent restrictor in
the rear vent of the fireplace outlet on
MPD-3530/4035/4540 series models, in any
installation that has a vertical vent run in
excess of three feet (0.914 meters).
FIREBOX TOP
VENT
COVER PLATE
COVER PLATE
SECURING SCREWS
(INSIDE UNIT)
CROSS SECTION
Figure 16
If needed, install the restrictor orientated as
shown, either from inside or outside the unit,
in the inner fireplace collar.
ON MPD-3530/4035/4540 SERIES MODELS
INNER FIREPLACE
COLLAR
APPLIANCE REAR
VENT OUTLET
(COMBINED TOP AND REAR VENT UNITS)
REAR VENT SEAL & COVER PLATE REMOVAL
WHEN USING THE REAR VENT
Step 4. INSTALLING VENT SYSTEM
COVER PLATE
VENT SEAL PLATE
GASKET
These instructions should be used as a
guideline and do not supersede local codes
in any way. Install venting according to local
codes,theseinstructions,thecurrentNational
Fuel Gas Code (ANSI-Z223.1) in the USA or
the current standards of CAN/CSA-B149.1
in Canada.
RESTRICTOR
SECURING SCREWS
LINTEL
SECURING
SCREWS
SECURING
SCREWS
REAR VENT
Figure 19
Ensure clearances are in accordance with
local installation codes and the requirements
of the gas supplier.
LINTEL
CABINET BACK
(OUTSIDE UNIT)
dégagementconformeauxcodesd'installa-
tion locaux et aux exigences du foumis-
seunde gaz.
(INSIDE UNIT)
CROSS SECTION
Figure 17
13
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
VERTICAL TERMINATION SYSTEMS (ROOF)
VENT SECTION LENGTH CHART
VENT SECTION LENGTH CHART
Nominal
T
O
T
A
L
T
O
T
A
L
Nominal Section
6
12
24
36
48
See Figure 20 and Figures 30 through 32
on Page 17 and their associated Vertical
Vent Tables, which illustrate the various verti-
cal venting configurations that are possible for
use with these appliances. Secure Vent™ pipe
applicationsareshownintheseFigures;Secure
Flex™ pipe may also be used. A Vertical Vent
Tablesummarizeseachsystem’sminimumand
maximum vertical and horizontal length values
that can be used to design and install the vent
components in a variety of applications.
Section Length
6
12
24
36
48
Length (inches)
(inches)
Net Section
4-1/2 10-1/2 22-1/2 34-1/2 46-1/2
Number of Vent Sections
Net Section
Length (inches)
4-1/2 10-1/2 22-1/2 34-1/2 46-1/2
Number of Vent Sections
Length (inches)
Height of Vent
Height of Vent
Q
T
Q
T
inches
144
ft
inches
4.5
ft
Y
Y
12
1
0
1
0
0
1
0
0
1
0
0
0
1
0
1
1
2
0
0
1
0
0
1
1
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
5
5
5
0
0
0
5
6
6
3
3
3
3
0
0
0
4
4
4
0
0
0
4
4
5
5
5
6
6
4
5
5
7
6
7
0.375
0.75
1
2
0
1
0
0
1
1
0
0
0
0
0
0
0
0
0
0
0
1
2
1
2
9
150
12.5
10.5 0.875
15 1.25
19.5 1.625
21 1.75
154.5 12.875
160.5 13.375
172.5 14.375
0
0
2
1
0
0
3
0
0
1
0
0
1
2
0
2
3
0
1
0
1
0
0
0
1
0
0
0
0
1
0
0
0
0
0
0
0
2
1
3
3
1
3
177
183
186
14.75
15.25
15.5
Both these vertical vent systems terminate
through the roof. The minimum vent height
above the roof and/or adjacent walls is speci-
fied in ANSI Z223.1-(latest edition) (In Canada,
the current CAN/CSA-B149.1 installation code)
by major building codes. Always consult your
localcodesforspecificrequirements.Ageneral
guide to follow is the Gas Vent Rule (refer to
Figure 5 on Page 6).
22.5 1.875
25.5 2.125
31.5 2.625
34.5 2.875
37.5 3.125
190.5 15.875
196.5 16.375
205.5 17.125
43.5 3.625
0
0
0
1
2
0
0
0
1
2
0
2
0
0
0
0
0
0
1
0
3
2
1
3
207
17.25
45
3.75
211.5 17.625
46.5 3.875
49.5 4.125
217.5 18.125
229.5 19.125
232.5 19.375
0
0
0
1
0
1
0
0
0
0
1
1
0
0
0
1
0
1
0
0
1
0
1
0
0
1
0
1
0
0
0
0
0
1
0
0
0
0
0
1
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
1
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
6
6
0
0
5
5
0
0
0
0
0
6
0
6
6
6
0
0
7
7
7
0
0
8
8
0
9
9
7
7
Vertical (Straight) Installation
(Figure 20)
51
4.25
1
0
0
0
0
0
1
1
0
0
0
0
0
1
1
0
1
0
2
0
0
0
0
1
0
2
0
0
0
0
0
2
1
2
3
0
3
0
0
0
1
2
0
1
0
0
0
1
0
0
2
0
2
2
1
0
0
0
2
0
1
0
0
0
0
0
0
0
0
1
1
1
2
0
2
2
3
2
4
3
2
4
3
3
2
4
3
2
4
3
0
5
55.5 4.625
Determine the number of straight vent sec-
tions required. 4-1/2" (114 mm), 10-1/2" (267
mm), 22-1/2" (572 mm), 34-1/2" (876 mm)
and 46-1/2" (1181 mm) net section lengths
are available (see Tables on this page and
Pages 35 and 36 - Vent Sections). Plan the
vent lengths so that a joint does not occur at
the intersection of ceiling or roof joists. Refer
to the Vent Section Length Chart.
237
19.75
0
6
57
66
4.75
5.25
241.5 20.125
7
7
246
252
264
276
279
20.5
21
7
8
67.5 5.625
7
8
69
72
5.75
6
22
7
8
23
8
8
73.5 6.125
79.5 6.625
23.25
0
6
280.5 23.375
283.5 23.625
289.5 24.125
301.5 25.125
310.5 25.875
8
9
81
90
6.75
7.5
0
7
0
7
SV4.5CGV-1
SV4.5FA or
91.5 7.625
0
7
Termination
SV4.5FB Flashing
93
96
7.75
8
9
9
AND SV4.5SC
Storm Collar
315
26.5
9
10
7
97.5 8.125
102 8.5
103.5 8.625
325.5 27.125
0
2
0
1
0
0
0
0
0
0
0
3
3
2
0
0
4
3
4
330
336
345
27.5
28
0
8
0
8
108
114
117
9
28.75
10
10
0
10
11
8
1 in (25.4 mm)
Minimum
Clearance to
Combustibles
9.5
9.75
0
1
1
0
1
0
0
0
1
2
0
1
0
0
0
0
0
0
0
5
0
1
1
6
0
0
0
0
0
3
3
3
0
4
0
4
2
0
0
0
0
0
0
3
0
4
6
5
4
5
6
4
3
5
349.5 29.125
372 31
118.5 9.875
126 10.5
130.5 10.875
376.5 31.375
379.5 31.625
418.5 34.875
0
9
11
0
11
9
SV4.5VF
Firestop/Spacer*
135
138
11.25
11.5
423
465
35.25
38.75
0
10
0
10 10
139.5 11.625
142.5 11.875
*When using Secure Flex,
use Firestop/Spacer
SF4.5VF.
Max. 40 ft
(12.2 m)
Effective Vent Length
Note: Convert inches into metric equivalent
measurement, as follows:
Model
Effective Length
SV4.5L6/12/24/36/48
Vent Sections
SV4.5L6
SV4.5L12
SV4.5L24
SV4.5L36
SV4.5L48
4-1/2"
10-1/2"
22-1/2"
34-1/2"
46-1/2"
Millimeters (mm) = Inches x 25.4
Centimeters (cm) = Inches x 2.54
Meters (M) = Inches x .0254
Table 7
Figure 20
14
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Vertical (Offset) Installation
All of the appliances covered in this document
are fitted with collars having locking inclined
channels. The dimpled end of the vent com-
ponents fit over the appliance collar to create
the positive twist lock connection.
Push the vent component against the previous
section until it fully engages, then twist the
componentclockwiserunningthedimplesdown
and along the incline channels until they seat at
the end of the channels.This seating position
is indicated by the alignment of the arrow and
dimple as shown in Figure 23.
Analyze the vent routing and determine the
quantities of vent sections and number of el-
bows required. Refer to Vertical Vent Figures
and Tables on page 14 to select the type of
vertical installation desired. Vent sections are
available in net lengths of 4-1/2" (114 mm),
10-1/2" (267 mm), 22-1/2" (572 mm), 34-1/2"
(876 mm) and 46-1/2" (1181 mm). Refer to the
Vent Section Length Chart on page 14 for an
aidinselectinglengthcombinations.Elbowsare
available in 90° and 45° configurations. Refer
to Figure 25 for the SV4.5E45 and SV4.5E90
elbow dimensional specifications.
First Vent
Component
Align the dimple (four places)
with the opening of the locking
incline channel on appliance
collar. Twist vent component
clockwise to engage and seal.
d. Install firestop/spacer at ceiling - When
usingSecureVent,useSV4.5VFfirestop/spacer
at ceiling joists; when using Secure Flex, use
SF4.5VF firestop/spacer. If there is living space
abovetheceilinglevel,thefirestop/spacermust
be installed on the bottom side of the ceiling.
If attic space is above the ceiling, the firestop/
spacer must be installed on the top side of
the joist. Route the vent sections through the
framed opening and secure the firestop/spacer
with 8d nails or other appropriate fasteners at
each corner. Remember to maintain 1" (25
mm) clearance to combustibles, framing
members, and attic or ceiling insulation
when running vertical chimney sections.
Attic insulation shield (96K94) may be used
to obtain the required clearances indicated
here. See installation accessories table on
pages 35 and 36.
Dimple
Locking
Incline Channel
Appliance collar
Where required, a telescopic vent section
(SV4.5LA) may be used to provide the installer
withanoptionininstallingintightand confined
spaces or where the vent run made up of fixed
length pieces develops a joint in a undesirable
location, or will not build up to the required
length. The SV4.5LA Telescopic Vent Section
has an effective length of from 1-1/2" (38 mm)
to 7-1/2" (191 mm). The SV4.5LA is fitted with
a locking inclined channel end (identical to a
normalventsectioncomponent)andaplainend
with 3 pilot holes. Slip the plain end over the
locking channel end of a standard SV4.5 vent
component the required distance and secure
with three screws.
Vent / Appliance Collar
Connection
Figure 22
Arrow
Align the dimple (four places) of the
upper vent section with the opening of
the locking incline channel on the
lower vent section. Twist vent
component clockwise to engage and
seal until arrow and dimple align.
Dimple
Locking
Incline Channel
E. Support the vertical vent run sections -
Note-Properventingsupportisveryimportant.
The weight of the vent must not be supported
by the fireplace in any degree.
Support the vertical portion of the venting
system every 8 feet (2.4m) above the fireplace
vent outlet. One method of support is by utiliz-
ing field provided support straps (conventional
plumber's tape). Secure the plumber's tape to
theframingmemberswithnailsorscrews.Loop
the tape around the vent, securing the ends of
the tape to the framing. If desired, sheet metal
screws#6x1/2"lengthmaybeusedtosecurethe
support straps to the vent pipe. See Figure 24.
Connected
Vent Sections
Arrow
Maintain a minimum 1" (25 mm) clearance to
combustiblematerialsforallverticalelements.
Clearances for all horizontal elements are 3"
(76 mm) on top, 1" (25 mm) on sides and 1"
(25 mm) on the bottom.
Vent / Vent Section
Connection
Arrow
Figure 23
To attach a vent component to the appliance
collar, align the dimpled end over the collar,
adjusting the radial alignment until the four
locking dimples are aligned with the inlet of
the four inclined channels on the collar (refer
to Figure 22 ). Push the vent component
against the collar until it fully engages, then
twist the component clockwise, running the
dimples down and along the incline channels
until they seat at the end of the channels. The
unitizeddesignoftheSecureVentcomponents
will engage and seal both the inner and outer
pipe without the need for sealant or screws.
If desired a #6 x 1/2" screw may be used at
the joint, but it is not required as the pipe will
securely lock when twisted.
A. Frame ceiling opening - Use a plumb line
from the ceiling above the appliance to locate
center of the vertical run. Cut and/or frame an
opening, 10-1/2" x 10-1/2" (267mm x 267mm)
inside dimensions, about this center mark
(Figure 21).
Min. 10-1/2"
(267 mm)
Min. 10-1/2"
(267 mm)
Blocking
Support Straps
(Plumber’s tape)
Note: An elbow may also be attached to the
appliance collar. Attach in the same manner
as you would a vent section.
8 feet (2.4 m)
Maximum
C.Attachventcomponentstoeachother-Other
vent sections may be added to the previously
installedsectioninaccordancewiththerequire-
ments of the vertical vent figures and tables.
To add another vent component to a length of
ventrun,alignthedimpledendovertheinclined
channel end of the previously installed section,
adjusting the radial alignment until the four
locking dimples are aligned with the inlets of
thefourinclinechannelsoftheprevioussection.
Figure 21
1 inch
B. Attach vent components to appliance -
Secure Vent SV4.5 direct vent system compo-
nents are unitized concentric pipe components
featuring positive twist lock connections (see
Figure 19 ).
(25.4 mm)
minimum
clearance to
combustibles
Figure 24
15
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
F.Changeventdirectiontohorizontal/inclined
run - At transition from or to a horizontal/in-
clined run, install the SV4.5E45 and SV4.5E90
elbows in the same manner as the straight vent
sections. The elbows feature a twist section to
allow them to be routed about the center axis
of their initial collar section to align with the
required direction of the next vent run element.
Twist elbow sections in a clockwise direction
only so as to avoid the possiblity of unlocking
anyofthepreviouslyconnectedventsections.
See Figure 25.
Storm
Collar
C
D
Framing dimensions for Roof
Pitch
0/12
C
d
Figure 28
10-1/2 in.
10-1/2 in.
(267 mm) (267 mm)
10-1/2 in. 12 in.
(267 mm) (305 mm)
10-1/2 in. 17-3/4 in.
(267 mm) (451 mm)
8-1/8"
K. Install the vertical termination - The final
step involves installation of the SV4.5CGV-1
Vertical Termination. Extend the vent sections
to the height as shown in the "Vertical vent ter-
mination section" on page 5. The SV4.5CGV-1
Vertical Termination (Figure 29 ) installs in the
exact same fashion as any other Secure Vent
section. Align the termination over the end of
the previously installed section, adjusting the
radial alignment until the four locking dimples
of the termination are aligned with the inlets of
thefourinclinechannelsofthelastventsection.
Pushtheterminationdownuntilitfullyengages,
thentwisttheterminationclockwiserunningthe
dimples down and along the incline channels
until they seat at the end of the channels.
4-13/16"
(206 mm)
6/12
(122 mm)
Swivel Joint
(360° swivel)
Swivel Joint
(360° swivel)
12/12
SV4.5E45
(45 Elbow)
SV4.5E90
(90 Elbow)
°
°
Figure 26
Figure 25
I. Install the roof flashing - Extend the vent
sections through the roof structure. Install the
roof flashing over the vent section and posi-
tion such that the vent column rises vertically
(use carpenters level) (Figure 27). Nail along
perimetertosecureflashingoradjustroofingto
overlap the flashing edges at top and sides only
andtrimwherenecessary.Sealthetopandboth
sides of the flashing with waterproof caulking.
G.Continueinstallationofhorizontal/inclined
sections - Continue with the installation of the
straight vent sections in horizontal/inclined run
as described in Step C. Install support straps
every5'(1.52m)alonghorizontal/inclinedvent
runs using conventional plumber’s tape. It is
very important that the horizontal/inclined
run be maintained in a straight (no dips) and
slightly elevated plane in a direction away
from the fireplace 1/4" per foot (20 mm per
meter) of horizontal vent. Use a carpenter’s
level to measure from a constant surface and
adjust the support straps as necessary.
It is important to maintain the required clear-
ancestocombustibles:1"(25mm)atallsides
for all vertical runs; and 3" (76 mm) at the
top, 1" (25 mm) at sides, and 1" (25 mm) at
the bottom for all horizontal/inclined runs.
H. Frame roof opening - Identify location for
vent at the roof. Cut and/or frame opening per
Roof Framing Chart and Figure 26.
Figure 27
j. Install the storm collar - Install the storm
collar, suppliedwiththeflashing, overthevent/
flashingjoint.SeeFigure28.Loosenthestorm
collar screw. Slide collar down until it meets
the top of the flashing. Tighten the adjusting
screw. Apply non-combustible caulking or
mastic around the circumference of the joint
to provide a water tight seal.
Figure 29
If the vent system extends more than 5' (1.5
m) above the roof flashing, stabilizers may be
necessary. Additional screws may be used at
section joints for added stability. Guide wires
may be attached to the joint for additional sup-
port on multiple joint configurations.
16
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
VERTICAL VENT FIGURES/TABLES
Ceiling
Firestop/Spacer
SV4.5VF*
TABLE A
H Maximum V Minimum
Note: Secure Vent (rigid vent pipe) is shown
in the figures; Secure Flex (flexible vent pipe)
may also be used.
(meters)
(meters)
(0.610)
(1.219)
(1.829)
(2.438)
feet
2
feet
1
*When using Secure Flex, use
Ceiling Firestop/Spacer SF4.5VF
(0.305)
(0.610)
(0.914)
(1.219)
Note: It is very important that the horizontal/
inclinedrunbemaintainedinastraight(nodips)
and recommended to be in a slightly elevated
plane, in a direction away from the fireplace of
1/4" rise per foot (20 mm per meter) which is
ideal, though rise per foot run ratios that are
smaller are acceptable all the way down to at
or near level.
4
2
6
3
V
8
4
V + H = 40 feet (12.2 meters) Max.
H = 8 feet (2.4 meters) Max.
Ratio V to H ratio is 1:2
This table shows a 1 (V) to 2 (H) ratio.
For every 1 foot of (V) vertical, you are
allowed 2 feet of (H) horizontal run, up
to a maximum horizontal run of 8 feet.
Note: SV4.5VF (Secure Vent), SF4.5VF (Secure
Flex)firestop/spacermustbeusedanytimevent
pipepassesthroughacombustiblefloororceil-
ing. SV4.5HF (Secure Vent), SF4.5HF (Secure
Flex)firestop/spacermustbeusedanytimevent
pipe passes through a combustible wall.
H
Example: If 8 feet of (H) horizontal vent
run is needed, then 4 feet minimum (V)
vertical vent will be required.
Note: Two 45 degree elbows may be used in
place of one 90 degree elbow. The same rise
to run ratios, as shown in the venting figures
for 90 elbows, must be followed if 45 degree
elbows are used.
Figure 31: Rear Vent - ONE 90-DEGREE ELBOW
TABLE B
Note: An elbow is acceptable as 1 foot of
vertical rise, except where an elbow is the
only vertical component in the system. (See
Figure 39 on page 21 ).
H Maximum
V Minimum
(meters)
Elbow Only
(0.305)
(meters)
(1.524)
(1.524)
(3.048)
(4.572)
(6.096)
feet
5
feet
H
5
1
2
3
4
Ceiling
Firestop/Spacer
SV4.5VF*
(0.610)
(0.914)
(1.219)
10
15
20
V + V + H = 40 feet (12.2 m) Max.
H = 20 feet (6.096 meters) Max.
1
Wall
Firestop/Spacer
SV4.5HF**
V1
Example: If 20 feet of (H) horizon-
tal vent run is needed, then 4 feet
minimum of (V) vertical vent will
be required.
Max. 40 ft
Ceiling
(12.2 m)
Firestop/
Spacer
V
SV4.5VF*
Thistableshowsa1(V)to5(H)ratio.
For every 1 foot of (V) vertical, you
are allowed 5 feet of (H) horizontal
run, up to a maximum horizontal
run of 20 feet.
*When using Secure Flex, use
Ceiling Firestop/Spacer SF4.5VF.
An elbow is acceptable as 1 foot of
vertical rise except where an elbow
istheonlyverticalcomponentinthe
system. See Figure 39.
**When using Secure Flex, use
Wall Firestop/Spacer SF4.5HF.
*When using
Secure Flex, use
Ceiling Firestop/
Spacer SF4.5VF.
Figure 32: Top Vent - TWO 90-DEGREE ELBOWS
A Vent Restrictor, as shown in Figure
18 on Page 13, must be used in this
application.
WARNING
Separate sections of concentric flexible vent pipe may NOT be joined
together under any circumstances.
Figure 30: Top Vent - STRAIGHT
17
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
VERTICAL VENT FIGURES/TABLES
(continued)
TABLE C
H Maximum
(meters)
H1
H+H Maximum
V Minimum
(meters)
feet
1
(meters)
(1.524)
(3.048)
(4.572)
(6.096)
feet
5
feet
(0.610)
(1.219)
(1.829)
(2.438)
(0.305)
(0.610)
(0.914)
(1.219)
2
4
6
8
1
2
3
4
Ceiling
Firestop/Spacer
SV4.5VF*
10
15
20
*When using Secure Flex, use
Ceiling Firestop/Spacer SF4.5VF.
**When using Secure Flex, use
Wall Firestop/Spacer SF4.5HF.
Wall
Firestop/Spacer
SV4.5HF**
V+V + H + H = 40 feet (12.2 m) Max
1
1
H = 8 feet (2.438 meters) Max.
H + H = 20 feet (6.096 meters) Max.
1
V1
Ceiling
Firestop/Spacer
SV4.5VF*
Example: If 20 feet of (H) horizontal vent run is needed,
then 4 feet minimum of (V) vertical vent will be required.
This table shows a 1 (V) to 5 (H) ratio. For every 1 foot of
(V) vertical, you are allowed 5 feet of (H) horizontal run, up
to a maximum horizontal run of 20 feet.
V
H
Figure 33: Rear Vent - THREE ELBOWS
TABLE D
V Minimum
(meters)
Elbow Only
(0.305)
H + H Maximum
1
Ceiling
Firestop/Spacer
SV4.5VF*
(meters)
(1.524)
(1.524)
(3.048)
(4.572)
(6.096)
feet
5
feet
Wall
Firestop/Spacer
SV4.5HF**
V
1
5
1
2
3
4
(0.610)
10
15
20
H
(0.914)
(1.219)
H + H = 20 feet (6.096 m) Max.
1
V + V + H + H = 40 ft. (12.192 m) Max.
1
1
V
H
1
Example: If 20 feet of (H) horizontal vent run is needed, then 4 feet
minimum of (V) vertical vent will be required.
*When using Secure Flex, use
Ceiling Firestop/Spacer SF4.5VF.
This table shows a 1 (V) to 5 (H) ratio. For every 1 foot of (V) verti-
cal, you are allowed 5 feet of (H) horizontal run, up to a maximum
horizontal run of 20 feet.
**When using Secure Flex, use
Wall Firestop/Spacer SF4.5HF.
An elbow is acceptable as 1 foot of vertical rise except where an
elbow is the only vertical component in the system. See Figure 39.
Figure 34: Top Vent - THREE ELBOWS
18
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
HORIZONTAL (OUTSIdE WALL)
TYPICAL HORIZONTAL VENT INSTALLATION
TERMINATION SYSTEM
Support
Horizontal / Inclined Run
Building
Support
Framing
Figures 35, and Figures 39 to 44 on pages
21 to 23 and their associated Horizontal Vent
Table illustrate the various horizontal venting
configurations that are possible for use with
theseappliances. SecureVentpipeapplications
are shown in these figures; Secure Flex pipe
may also be used. A Horizontal Vent Table sum-
marizeseachsystem’sminimumandmaximum
vertical and horizontal length values that can be
used to design and install the vent components
in a variety of applications.
Brackets
SV4.5HT-2
Termination
SV4.5E90
Elbow
Exterior
Wall
SV4.5L6/12/24/36/48
Vent Sections
Ceiling
Firestop/Spacer
Vertical
Rise
Support bracket spacing
SV4.5HT-2
Termination
every 5 ft (1.52 m)
Bothofthesehorizontalventsystemsterminate
through an outside wall. Building Codes limit
or prohibit terminating in specific areas. Refer
to Figure 8 on page 7 for location guidelines.
See Figure 24 on page 15 for
vertical vent section support.
Exterior
Wall
Fireplace
SecureVentSV4.5directventsystemcomponents
areunitizedconcentricpipecomponentsfeaturing
positivetwistlockconnection,(refertoFigure22
onpage15). Alloftheappliancescoveredinthis
document are fitted with collars having locking
inclined channels. The dimpled end of the vent
componentsfitovertheappliancecollartocreate
the positive twist lock connection.
Figure 35
The unitized design of the Secure Vent compo-
nents will engage and seal both the inner and
outer pipe elements with the same procedure.
Sealant and securing screws are not required.
G. Support the vertical run sections -
On the vertical run, support the venting sys-
tem every 8 feet (2.4m) above the fireplace
vent outlet with field provided support straps
(Plumber's tape). Attach the straps to the vent
pipe and secure to the framing members with
nails or screws. See Figure 24 on page 15.
Note: An elbow may also be attached to the
appliance collar. Attach in the same manner
as you would a vent section.
A. Plan the vent run -
Analyze the vent routing and determine the
types and quantities of sections required
4-1/2"(114mm),10-1/2"(267mm),22-1/2"(572
mm),34-1/2"(876mm)and46-1/2"(1181mm)net
section lengths are available. It is recommended
that you plan the venting so that a joint does not
occurintheceilingorroofjoists. Allowforelbows
as indicated in Figure 25 on page 16.
H. Changeventdirection- Attransitionfromor
toahorizontal/inclinedrun,installtheSV4.5E45
and SV4.5E90 elbows in the same manner as
the straight vent sections. The elbows feature
atwistsectiontoallowthemtoberoutedabout
the center axis of their initial collar section to
align with the required direction of the next
vent run element. Twist elbow sections in a
clockwise direction only so as to avoid the
possiblity of unlocking any of the previously
connected vent sections. See Figure 25 on
page 16.
E. Attachventcomponentstoeachother-Other
vent sections may be added to the previously
installedsectioninaccordancewiththerequire-
ments of the vent tables. To add another vent
component to a length of vent run, align the
dimpled end of the component over the inclined
channel end of the previously installed section,
adjustingtheradialalignmentuntilthefourlock-
ingdimplesarealignedwiththeinletsofthefour
incline channels of the previous section. Push
theventcomponentagainsttheprevioussection
until it fully engages, then twist the component
clockwise running the dimples down and along
the incline channels until they seat at the end of
thechannels.Thisseatingpositionisindicated
by the alignment of the arrow and dimple as
shown in Figure 23 on page 15.
Maintain a minimum 1" (25 mm) clearance to
combustiblesontheverticalsections.Clearances
for the horizontal runs are; 3" (76 mm) on top, 1"
(25mm)onsides, and1"(25mm)atthebottom.
B. Frame exterior wall opening -
Locate the center of the vent outlet on the ex-
terior wall according to the dimensions shown
in Figure 9 on page 8. Cut and/or frame an
opening, 10-1/2" x 12-1/8" (267 mm x 308mm)
inside dimensions, about this center.
I. Continueinstallationofhorizontal/inclined
sections - Continue with the installation of the
straightventsectionsinhorizontal/inclinedrun
as described in Step E. Install support straps
every 5 ft. (1.52 m) along horizontal/inclined
vent runs using conventional plumber’s tape.
See Figure 35, it is very important that the
horizontal/inclined run be maintained in a
straight (no dips) and recommended to be in
a slightly elevated plane, in a direction away
from the fireplace of 1/4" rise per foot (20 mm
per meter) which is ideal, though rise per foot
runratiosthataresmallerareacceptableallthe
way down to at or near level. Use a carpenter’s
level to measure from a constant surface and
adjust the support straps as necessary.
C. Frame ceiling opening - If the vertical route
istopenetrateaceiling, useplumblinetolocate
thecenterabovetheappliance.Cutand/orframe
an opening, 10-1/2" x 10-1/2" (267 mm x 267
mm)insidedimensions,aboutthiscenter(refer
to Figure 21 on page 15 ).
F. Install firestop/spacer at ceiling -
WhenusingSecureVent,useSV4.5VFfirestop/
spaceratceilingjoists;whenusingSecureFlex,
use SF4.5VF firestop/spacer. If there is living
space above the ceiling level, the firestop/
spacer must be installed on the bottom side of
the ceiling. If attic space is above the ceiling,
the firestop/ spacer must be installed on the
top side of the joist. Route the vent sections
through the framed opening and secure the
firestop/spacerwith8dnailsorotherappropriate
fasteners at each corner.
d. Attach vent components to appliance - To
attach a vent component to the appliance collar,
alignthedimpledendoverthecollar,adjustingthe
radialalignmentuntilthefourlockingdimplesare
alignedwiththeinletsofthefourinclinechannels
on the collar (refer to Figure 22 on page 15).
It is important to maintain the required clear-
ancestocombustibles:1"(25mm)atallsides
for all vertical runs; and 3" (76 mm) at the
top, 1" (25 mm) at sides, and 1" (25 mm) at
the bottom for all horizontal/inclined runs.
Push the vent component against the collar until it
fullyengages,thentwistthecomponentclockwise,
running the dimples down and along the incline
channels until they seat at the end of the channels.
Remember to maintain 1" (25 mm) clearance
to combustibles, framing members, and attic
or ceiling insulation when running vertical
chimney sections.
19
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
j. Assemble vent run to exterior wall - If not
Firestop/Spacer (SV4.5HF) shown
on the exterior side of the wall. It
may also be installed on the
interior side.
previously measured, locate the center of the
vent at the exterior wall. Prepare an opening as
described in Step B. Assemble the vent system
to point where the terminus of the last section
is within 7 in. (178 mm) to 11-1/4 in. (286
mm) inboard of the exterior surface to which
the SV4.5 HT termination is to be attached, see
Figure 37. If the terminus of the last section
is not within this distance, use the telescopic
vent section SV4.5LA, as the last vent section.
For wall thicknesses greater than that shown in
Figure37,refertoTable8onpage21.Thistable
liststheadditionalventingcomponentsneeded
(in addition to the termination and adapter) for
a particular range of wall thicknesses.
SV4.5HT-2
Termination
7"
(178)
10-1/2"
12-1/8"
(267mm)
(308 mm)
5-1/8"
(130 mm)
3"
(76 mm)
1"
Adapter
SV4.5RCH
(25.4 mm)
Note: Centerline of Vent Piping is
NOT the Same as the Centerline of
the Framed Opening.
K. Attach termination adapter - Attach the
adapter(adapter-SV4.5RCH-providedwiththe
termination) to the vent section or telescoping
ventsection),elboworappliancecollarasshown
in Figure 36 in the same manner as any SV4.5
vent component (refer to Step E).
See Figure 13 on page 11
for Min. Distance to Base
of Appliance.
6 to 48 inch Vent Section,
Telescopic vent section,
Elbow or Appliance Collar
Base of Appliance
Installing the Square Horizontal Termination (SV4.5HT-2)
Figure 36
L. Install Firestop/Spacer at exterior wall
-
When using the square termination, install
*Use silicone caulking to seal
the top and sides of the
termination, up to the
underlayment, stucco, or
masonry wall surface.
SV4.5HF (Secure Vent), SF4.5HF (Secure Flex)
Firestop/Spacerovertheopeningattheexterior
sideoftheframing, longsideup, withthe3inch
spacer clearance at the top as shown in Figure
36, and nail into place.
Maximum wall thickness
10 in.(254 mm)**
Interior Surface of
Finished Wall
Exterior Surface of Siding
Exterior Surface of
Framing
Maximum Extent of
Vent Run Sections
Relative to Exterior
Surface of Framing
Siding
*Caulk
(The Firestop/Spacer may also be installed over
the opening at the interior side of the framing.)
6 in. to 9-1/4 in.
(152 to 235 mm)**
Last Vent Section. Use
Telescopic Vent
Section (SV4.5LA), If
Necessary
M. Install the desired termination -
1. Installthesquaretermination(SV4.5HT-2
or SV4.5HTSS)- For the last step , from out-
side the exterior wall, slide the collars of the
termination onto the adapter (the outer over
the outer and the inner inside the inner) until
the termination seats against the exterior wall
surface to which it will be attached. Orient
the housing of the termination with the arrow
pointed upwards. Secure the termination to
the exterior wall. The horizontal termination
must not be recessed into the exterior wall
or siding by more than the 1-1/4" (32 mm) as
shown in Figure 37.
SV4.5HT-2
Square Termination
*Caulk
SV4.5HT-2
Square Termination
Adapter
SV4.5RCH
1-1/4" Maximum Recess of
the Square Termination into
Exterior Finishing Material
**For thicknesses greater
than 10 inches, see Table 8.
Stucco
Venting Connection and Exterior Wall Recessing of the
Horizontal Square Termination (SV4.5HT-2).
Figure 37
SVHRK Snorkel Cap –The snorkel cap is
designed to be fitted into a basement window
box. The SVHRK cap is for use with flex vent
Theverticaldistancebetweentheinletandoutlet
of the cap is 28 in. (711 mm). pipe.
Horizontal terminations have been designed to perform in a wide range of weather
conditions. Our terminations meet or exceed industry standards.
When selecting the locations of your horizontal terminations, do not place the termination
where water from eaves and adjoining rooflines may create a heavy flow of cascading water
onto the termination cap. If the cap must be placed where the possibility of cascading water
exists, it is the responsibility of the builder to direct the water away from the termination
cap by using gutters or other means.
IMPORTANT: The vent termination is hot
while in operation and for a period of
time following the use of the fireplace.
To prevent contact with hot surfaces,
we recommend the use of a Termina-
tion Guard. See Page 36. This can be
purchased at your local dealer.
Take care to carefully follow the installation instructions for the termination, including the
use of silicone caulking where required.
20
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
HORIZONTAL VENT FIGURES/TABLES
TABLE F
Note: Secure Vent components (rigid vent pipe and terminal) are
shown in the figures; Secure Flex components (flexible vent pipe and
terminal) may also be used.
H Maximum
V Minimum
(meters)
(meters)
(0.914)
feet
3
feet
Elbow Only
Note: Two 45 degree elbows may be used in place of one 90 degree
elbow. The same rise to run ratios, as shown in the venting figures for
90 elbows, must be followed if 45 degree elbows are used.
H
V
Note:Itisveryimportantthatthehorizontal/inclinedrunbemaintained
in a straight (no dips) and recommended to be in a slightly elevated
plane, in a direction away from the fireplace of 1/4" rise per foot (20
mm per meter) which is ideal, though rise per foot run ratios that are
smaller are acceptable all the way down to at or near level.
Note:SV4.5VF(SecureVent),SF4.5VF(SecureFlex)firestop/spacermust
be used anytime vent pipe passes through a combustible floor or ceiling.
SV4.5HF (Secure Vent), SF4.5HF (Secure Flex) firestop/spacer must be
used anytime vent pipe passes through a combustible wall.
**When using Secure
Flex, use Wall Firestop/
Spacer SF4.5HF.
Wall Firestop/
Spacer
SV4.5HF**
Square termination (SV4.5HT-2) shown.
See Table 3 as an aid in venting component selection
for a particular range of exterior wall thicknesses.
WARNING
Under no circumstances, may separate sections of
concentric flexible vent pipe be joined together.
Figure 39: Top Vent - ONE 90-DEGREE ELBOW -
ELBOW CONNECTION AT APPLIANCE
Venting Components Required for Various Exterior Wall Thick-
nesses, when using Typical Termination Kits
Example: If 20 feet of (H)
horizontal vent run is needed,
then 4 feet minimum of (V)
vertical vent will be required.
TABLE G
H Maximum V Minimum
Vent Components Required Exterior Wall Thickness - inches (mm)
Termination Kit Only
6 to 9-1/4 (152 to 235)
(meters)
(1.524)
(3.048)
(4.572)
(6.096)
(meters)
(0.305)
(0.610)
(0.914)
(1.219)
feet
5
feet
1
TerminationKitand 6In.Vent
Section (SV4.5L6)
This table shows a 1 (V) to 5
(H) ratio. For every 1 foot of
(V) vertical, you are allowed
5 feet of (H) horizontal run,
up to a maximum horizontal
run of 20 feet.
10-3/4 to 14 (273 to 356)
10
15
20
2
Termination Kit and 12 in.
Vent Section (SV4.5L12)
3
16-3/4 to 20 (426 to 508)
4
Termination Kit and Tele-
scopic Section (SV4.5L12)
11-3/4 to 20 (299 to 508)
V + H = 40 feet (12.2 m) Max.
H = 20 ft. (6.096 m) Max.
Note: See Figure 37 showing wall thickness range
when using SV4.5HT-2 termination kit.
Table 8
H
H = 28 in. (711 mm) Maximum.
H
V
Wall Firestop/
Spacer
SV4.5HF**
Ceiling
7 in
(178 mm)
Firestop/
Spacer
Wall Firestop/
Spacer SV4.5HF**
SV4.5VF*
*When using Secure Flex, use
Ceiling Firestop/Spacer SF4.5VF.
**When using Secure Flex, use
Wall Firestop/Spacer SF4.5HF.
**When using Secure Flex, use
Wall Firestop/Spacer SF4.5HF.
Square termination (SV4.5HT-2) shown.
Only the square termination (SV4.5HT-2) may be used.
See Table 8 as an aid in venting component selection
for a particular range of exterior wall thicknesses.
See Table 8 as an aid in venting component selection
for a particular range of exterior wall thicknesses.
Figure 40: Top Vent - ONE 90-DEGREE ELBOW -
Figure 38: Rear Vent - NO ELBOWS
ELBOW CONNECTION NOT DIRECTLY AT APPLIANCE
21
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
HORIZONTAL VENT FIGURES/TABLES (continued)
TABLE H
H
V Minimum
(meters)
feet
1 Maximum
(meters)
(1.524)
H Maximum
(meters)
H
+H
H
1
feet
5
feet
2
4
6
8
(0.610)
(1.219)
(1.829)
(2.438)
1
2
3
4
(0.305)
(0.610)
(0.914)
(1.219)
(3.048)
10
15
20
Ceiling
Firestop/Spacer
SV4.5VF*
(4.572)
(6.096)
V + H + H = 40 feet (12.2 m) Max.
1
Wall Firestop/
Spacer
SV4.5HF**
H = 8 feet (2.438 meters) Max.
H + H = 20 feet (6.096 meters) Max.
1
V
Example: If 20 feet of (H) horizontal vent run is needed,
then 4 feet minimum of (V) vertical vent will be required.
This table shows a 1 (V) to 5 (H) ratio. For every 1 foot of
(V) vertical, you are allowed 5 feet of (H) horizontal run,
up to a maximum horizontal run of 20 feet.
*When using Secure Flex, use
Ceiling Firestop/Spacer SF4.5VF.
See Table 8 on page 21 as an aid in venting component
**When using Secure Flex, use
Wall Firestop/Spacer SF4.5HF.
selection for a particular range of exterior wall thicknesses.
Square termination (SV4.5HT-2) shown.
Figure 41: Rear Vent - TWO 90-DEGREE ELBOWS
TABLE J
Wall Firestop/Spacer
SV4.5HF**
V Minimum
(meters)
H + H Maximum
1
(meters)
(0.914)
(1.524)
(3.048)
(4.572)
(6.096)
feet
3
feet
H
Elbow Only
5
1
(0.305)
(0.610)
(0.914)
(1.219)
H
1
10
15
20
2
3
4
V
V + H + H = 40 feet (12.2 m) Max.
1
Wall Firestop/Spacer
SV4.5HF**
H + H = 20 ft. (6.096 m) Max.
*When using Secure Flex, use
Ceiling Firestop/Spacer SF4.5VF.
1
**When using Secure Flex, use
Wall Firestop/Spacer SF4.5HF.
Example: If 20 feet of (H) horizontal vent run
is needed, then 4 feet minimum of (V) vertical
vent will be required.
Ceiling Firestop/Spacer
SV4.5VF*
This table shows a 1 (V) to 5 (H) ratio. For
every 1 foot of (V) vertical, you are allowed 5
feet of (H) horizontal run, up to a maximum
horizontal run of 20 feet.
Square termination (SV4.5HT-2) shown.
See Table 8 on page 21 as an aid in venting component
selection for a particular range of exterior wall thicknesses.
An elbow is acceptable as 1 foot of vertical
rise except where an elbow is the only vertical
component in the system. See Figure 39.
Figure 42: Top Vent - TWO 90-dEGREE ELBOWS
22
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
HORIZONTAL VENT FIGURES/TABLES (continued)
TABLE K
Wall Firestop/Spacer
SV4.5HF**
H+ H + H Maximum
H Maximum
V Minimum
1
2
feet
(meters)
feet
feet (meters)
(meters)
(0.610)
(1.219)
(1.829)
(2.438)
5
(1.524)
(3.048)
(4.572)
(6.096)
2
4
6
8
1
2
3
4
(0.305)
(0.610)
(0.914)
(1.219)
H
1
10
15
20
H
2
V + H + H + H = 40 feet (12.2 m) Max.
1
2
*When using Secure Flex, use
Ceiling Firestop/Spacer SF4.5VF.
**When using Secure Flex, use
Wall Firestop/Spacer SF4.5HF.
H = 8 feet (2.438 meters) Max.
1
H + H + H = 20 feet (6.096 meters) Max.
Ceiling
Firestop/Spacer
SV4.5VF*
2
Example: If 20 feet of (H) horizontal vent run
is needed, then 4 feet minimum of (V) vertical
vent will be required.
V
This table shows a 1 (V) to 5 (H) ratio. For every
1 foot of (V) vertical, you are allowed 5 feet of
(H) horizontal run, up to a maximum horizontal
run of 20 feet.
H
Square termination (SV4.5HT-2) shown.
See Table 8 on page 21 as an aid in venting component selection for a particular range of exterior wall thicknesses.
Figure 43: Rear Vent - THREE 90-DEGREE ELBOWS
TABLE L
*When using Secure Flex, use
Ceiling Firestop/Spacer SF4.5VF.
**When using Secure Flex, use
Wall Firestop/Spacer SF4.5HF.
H Maximum
V Minimum
H
1
(meters)
(meters)
feet
feet
5
Elbow Only
(1.524)
(1.524)
(3.048)
(4.572)
(6.096)
(0.305)
(0.610)
(0.914)
(1.219)
5
1
2
3
4
Ceiling
Firestop/Spacer
SV4.5VF*
10
15
20
H
Wall Firestop/Spacer
SV4.5HF**
H + H = 20 feet (6.096 m) Max.
1
V
V + V + H + H = 40 ft. (12.192 m) Max.
1
1
1
V
Example: If 20 feet of (H) horizontal vent
run is needed, then 4 feet minimum of (V)
vertical vent will be required.
This table shows a 1 (V) to 5 (H) ratio. For
every1footof(V)vertical,youareallowed5
feet of (H) horizontal run, up to a maximum
horizontal run of 20 feet.
Wall Firestop/Spacer
SV4.5HF**
An elbow is acceptable as 1 foot of vertical
riseexceptwhereanelbowistheonlyverti-
calcomponentinthesystem. SeeFigure39.
Square termination (SV4.5HT-2) shown.
See Table 8 on page 21 as an aid in venting component
selection for a particular range of exterior wall thicknesses.
Figure 44: Top Vent - THREE 90-DEGREE ELBOWS
23
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
VERTICAL OR HORIZONTAL VENTING USING
SECuRE FlEx KITS ANd COMPONENTS
FLEX VENT
NOTE: OUTER PIPE IS PULLED AWAY TO
SHOW THE DETAIL OF THE INNER PIPE
Secure Flex venting kits and components may
be used in any venting application where rigid
Secure Vent (SV4.5) direct vent components
can be used. All restrictions, clearances and
allowances that pertain to the rigid piping apply
to the flexible venting. Secure Flex kits may
notbemodified;also,undernocircumstances
may separate sections of flex pipe be joined
together. Secure Flex kits may be added to
the end of a vent run made up of rigid Secure
Vent (SV4.5) vent sections provided that doing
so does not violate any of the venting length,
height, routing, horizontal to vertical ratio re-
quirementsorclearanceconsiderationsdetailed
in this manual.
SECURING SCREW
(3 PLACES EQUALLY SPACED
JUST BELOW GEAR CLAMP)
Apply ONLY MIL-PAC BLACK HIGH
TEMPERATURE SEALANT (Catalog No.
10K81) to the outside surface of both
collars of the adapter (be especially
careful to fill the grooves of the outer
collar to be covered by the flexible
pipe) and slide flexible pipe over
inner and outer adapter collars.
GEAR
CLAMPS
1-3/4 in. (44 mm)
Flexible Pipe and
Adapter Outer
1-3/4 in. (44 mm)
Flexible Pipe and
Adapter Inner
Collar Overlap
SecureFlexkitscomewithanincludedadapter
that can be fitted to the appliance collar or the
inclined channel end of the last Secure Vent
(SV4.5) vent section in a rigid system in the
exact same fashion as any other Secure Vent
section. Align the dimpled end of the adapter
overthepreviouslyinstalledsectionorappliance
collar, adjusting the radial alignment until the
four locking dimples of the adapter are aligned
with the inlets of the four incline channels of
the last vent section or collar. Push on the
adapter until it fully engages, then twist the
adapter clockwise running the dimples down
and along the incline channels until they seat
at the end of the channels.
Collar Overlap
Adapter
(SV4.5RF)
SECURING SCREW
(3 PLACES EQUALLY SPACED
JUST BELOW GEAR CLAMP)
Attach Adapter to Appliance
Collar, or Secure Vent Sections
Figure 45
Seetheappropriatesectionsandfiguresshown
throughout the venting section for their instal-
lation requirments.
2. ApplyabeadofMill-PacBlack(700°F)high
temperature sealant - Catalog No. 10K81) to
the outer adapter collar; to the grooves of the
collar which extend approximately 1 inch from
the end and to the flat surface, approximately
1-3/8 inches from the end.
3. Pull and extend the outer flexible vent pipe.
4. Slide the outer flex pipe over the adapter
collar. Ensure the flexible vent pipe completely
engages the adapter collar to a distance of 1³⁄₄
inches from the end, and that it is free from
damage or tears.
5. Slide the gear clamp down and tighten it
fully to secure the flexible vent to the adapter
outer collar approximately 3/4 inch from the
end of the flex.
6. Install three screws 120 degrees apart
through the flexible vent pipe and into the
adapter collar just below the gear clamp to
provide additional security to the connection.
Flexible Vent Section
Attach the flexible vent to the adapter as fol-
lows (see Figure 45):
A. Install the Inner Flex Pipe -
1. Install the small gear clamp loosely around
the inner flexible vent pipe, push it back out
of the way.
2. ApplyabeadofMill-PacBlack(700°F)high
temperature sealant - Catalog No. 10K81) to
the inner adapter collar, approximately 1/2 inch
from the end.
3. Pull and extend the inner flexible vent pipe.
4. Slide the inner flex pipe over the adapter
collar. Ensure the flexible vent pipe completely
engages the adapter collar to a distance of
1-3/4 inches from the end, and that it is free
from damage or tears.
5. Slide the gear clamp down and tighten it
fully to secure the flexible vent to the adapter
inner collar approximately 3/4 inch from the
end of the flex.
5" (127 mm)
Radius Minimum
Figure 46
E. Attach Flex Vent to Termination -
Secure Flex components can be purchased
separately and attached to bulk lengths of
Secure Flex flexible tubing cut to size at the
job site. Secure the flexible vent to the Secure
Flex terminations in the same manner (see
Figure 45 ) as it was attached to the adapter.
C. Route Flex Vent -
Ensure that the flex vent is properly routed to
provide the required clearance. Do Not allow
the flexible vent to bend in a radius tighter than
5" (127 mm). Refer to Figure 46. Support
horizontal sections of flex with metal straps at
2 foot (0.61 m) intervals.
Note: Secure Flex vent must be attached
to Secure Flex terminations only. dO NOT
substitute Secure Vent terminations or the
Secure Vent adapter for Secure Flex compo-
nents.ThecollarsofSecureFlexterminations
and adapters have a different circumference
than that used with the Secure Vent pipe.
Additionally, Secure Flex components have
an extended length center tube for use in
attaching the flexible vent.
6. Install three screws 120 degrees apart
through the flexible vent pipe and into the
adapter collar just below the gear clamp to
provide additional security to the connection.
d. Install Firestop/Spacers at ceilings and walls -
When Secure Flex penetrates a wall or ceiling,
a firestop/spacer is required: use the SF4.5 VF
firestop/spacer for ceilings and the SF4.5 HF
firestop/spacer for walls.
B. Install the Outer Flex Pipe -
1. Install the large gear clamp loosely around
the outer flexible vent pipe, push it back out
of the way.
24
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Refer to Section A for millivolt appliances and
Step 5. FIELd WIRING
Electronic Wiring Diagram (Honeywell)
Showing the Blower Wiring for the Optional
FBK-100 and FBK-200 Kits
1. If any of the original wire as supplied must be replaced,
1. it must be replaced with Type AWM 105°C – 18 GA. wire.
2. 120V, 60Hz – Less than 3 amps.
Section B for electronic appliances. The gas
valve is set in place and pre-wired at the factory
on both models.
CAUTION
The ground supply lead must be
connectedtothewireattachedtothe
green ground screw located on the
outlet box (see wiring diagrams).
Failure to do so will result in a
potential safety hazard. The appli-
ancemustbeelectricallygrounded
in accordance with local codes or,
in the absence of local codes, the
National Electrical Code, ANSI/
NFPA 70-latest edition (in Canada,
the current CSA C22-1 Canadian
Electrical Code).
A. Millivolt Wiring (see Figure 47)
**Leave the ON/OFF switch, which is integral
with the gas valve, in the ON position.
**ON/OFF Switch (Integral
with Gas Valve)
Millivolt units are not provided with any
factory-installed controls; therefore, one of the
optional control switches is required to operate
the unit (ON/OFF Wall Switch, Unit-Mountable
ON/OFF Switch*, Thermostat, Remote Control).
See the fireplace Care and Operation Instruc-
tions for details.
Gas Valve
PILOT
ASSEMBLY
BK
R
Green
BL
White
Black
Ground - Green
Neutral - White
120 VAC - Black
OPT
BLOWER
Junction Box
Tab Intact
Tab
Broken
[*If using a Unit-Mountable ON/OFF Rocker Switch
with an optional Style View Door, mount the Rocker
Switch on the door instead of the unit.]
Red
Optional
Accessory
Switch
Green
Ground
Screw
Hot
Neutral
Side of
Side of
Receptacle
Receptacle
W
Transf.
120 V.
B
G
1. If installing an ON/OFF wall switch or ther-
mostat, mount it in a convenient location on
a wall near the fireplace.
24 V
BL
R
CAUTION: Label all wires prior to discon-
nection when servicing controls. Wiring
errors can cause improper and dangerous
operation.
W
2. Wire the control switch within the millivolt
control circuit using the 15 feet of 2 con-
ductor wire supplied with the unit.
BK
OPTIONAL APPLIANCE-MOUNTED ON/OFF SWITCH
OR OPTIONAL WALL SWITCH
OR OPTIONAL THERMOSTAT
OR OPTIONAL REMOTE RECEIVER
Note: The supplied 15 feet of 2 conductor
wire has one end of each conductor con-
nected to the gas valve circuit and the other
end of each conductor placed loose inside
the bottom compartment.
ATTENTION: Au moment de l’entretien
des commandes, étiquetez tous les fils
avant de les débrancher. des erreurs
de cáblage peuvent entraîner un fonc-
tionnement inadéquat et dangereux.
*Blower speed control switch is provided in FBK200 blower kit.
Factory Wired
Field Wired
Schematic Representation Only
Figure 48
Verify proper operation after servicing.
S’assurerquel’appareilfonctionneadé-
quatement une fois l'entretien terminé.
CAUTION
In millivolt systems, do NOT connect
a Wall Switch to a 120V power supply.
Electronic Wiring Diagram (Honeywell)
Showing the Blower Wiring for the Optional
FBK-250 Kits
1. If any of the original wire as supplied must be replaced,
1. it must be replaced with Type AWM 105°C – 18 GA. wire.
2. 120V, 60Hz – Less than 3 amps.
WIRING DIAGRAM MILLIVOLT GAS VALVES
B. Electronic Wiring (see Figures 48 & 49)
THERMOPILE
APPLIANCE- MOUNTED
ON/OFF SWITCH
The electronic gas valve has an integrated ON/
OFF burner control switch. One of the follow-
ing optional controls also may be used: ON/
OFF Wall Switch, Thermostat, Remote Control
(see fireplace Care and Operation Instructions
for details.).
*Leave the ON/OFF switch, which is integral
with the gas valve, in the ON position.
*ON/OFF Switch (Integral
with Gas Valve)
(OPTIONAL)
TP-TH
Gas Valve
TP
TH
PILOT
ASSEMBLY
Ground - Green
Neutral - White
120 VAC - Black
BK
GAS VALVE
BK/W(1)
BK/W(1)
Optional
FBK-250
Module
R
BL
Green
White
Black
Note: Electronic models must be connected to
the main power supply.
OPT
BLOWER
Junction Box
WALL-MOUNTED ON/OFF SWITCH (OPTIONAL)
THERMOSTAT (OPTIONAL)
Tab Intact
Tab
Broken
1. Route a 3-wire 120Vac 60Hz 1ph power
Red
Optional
Accessory
Switch
supply to the appliance junction box.
Green
Ground
Screw
WALL MOUNTED CONFIGURATION FOR FAN SWITCH (OPTIONAL)
Hot
Neutral
Side of
Side of
Receptacle
Receptacle
2. Remove the electrical inlet cover plate from
the side of the unit by removing the plate’s
securing screws (see Figure 13, Page 11).
W
B
Transf.
120 V.
G
24 V
3. Remove the cover plate knockout; then feed
the power supply wire through the knockout
opening and into the unit junction box.
BL
R
WH
BK
BK
R
4. See Figures 48 & 49. Connect the black
power supply wire to the lower outlet’s red
pigtail lead.
W
OPTIONAL APPLIANCE-MOUNTED ON/OFF SWITCH
OR OPTIONAL WALL SWITCH OR OPTIONAL THERMOSTAT
OR OPTIONAL REMOTE RECEIVER
GR
Factory Wired
Field Wired
FAN
(OPTIONAL)
Connect the white power supply wire to the
outlet’s common terminal.
JUNCTION BOX
Schematic Representation Only
Figure 49
5. Connect the ground supply wire to the
pigtail lead attached to the outlet’s green
ground screw.
Figure 47
25
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Note: Remotereceivershouldbe locatedinthe
A sediment trap is recommended in the gas
piping within the home to prevent moisture
and debris in the line from damaging the valve.
120V, 60HZ, 1PH
wall, or if installed in the control compartment,
pulledallthewayforwardandcompletelytothe
left or right against the corner posts.
* Wall-mounted
ON/ OFF Blower
Switch or Variable
Speed Control Switch.
These appliances are equipped with a gas flex
lineforuse(wherepermitted)inconnectingthe
unit to the gas line. A gas flex line is provided
to aid in attaching the direct vent appliance to
the gas supply. The gas flex line can only be
used where local codes permit. Refer to Figure
51 for flex line description. The flex line is rated
for both natural and propane gas. A manual
shut off valve is also provided with the flex line.
6. Ifwall-mountedON/OFFcontrolorthermo-
stat is to be used, mount it in a convenient
location on a wall near the fireplace.
7. If an optional control is to be used, wire it in
the low voltage circuit as shown in Figures
48 and 49.
Junction Box
Note: The supplied 15 feet of 2 conductor wire
has one end of each conductor connected to
the gas valve circuit and the other end of each
conductor placed loose inside the bottom
compartment.
The gas control valve is located in the lower
control compartment.
Tab
Broken
Hot
Side of
Red
To access the valve open the lower control
compartment door (see Figure 52) by pushing
in the right top corner of the door. (The door
is hinged at the bottom.) Remove the bottom
compartment door by sliding the hinge pin,
located at the door’s left side, to the right until
it disengages from the left corner post hole.
Pull the door diagonally to the left, away from
the fireplace.
Black
Receptacle
8. If the optional control switch is installed,
turn the appliance-mounted ON/OFF burner
control switch to the OFF position.
9. After the wiring is complete, replace the
Neutral
Side of
cover plate.
Receptacle
Note: The gas valve-mounted ON/OFF switch
is shown in Figures 48 and 49. It is integral
with the gas valve and should be set to the
ON position.
Plug blower
Tab Intact
into this
Green
Ground
Screw
receptacle
The millivolt control valve has a 3/8"
(10mm) NPT thread inlet port. The electronic
control valve has a 1/2" (13 mm) NPT thread
inletportandisfittedwitha1/2"x3/8"(13mmx
10mm) NPT fitting.
Blower
Field Wired
Factory Wired
Ground
WARNING
Figure 50: Junction Box Wiring
Electronicmodelsoftheseappli-
ancesareequippedwithathree-
prong (grounding) plug utilized
in connecting the electronic
components to the junction box
in the lower compartment. This
groundingplugprovidesprotec-
tion against shock hazard and
should be plugged directly into
the properly grounded three-
prong receptacle. dO NOT cut
or remove the grounding prong
from the plug.
Secure all joints tightly using appropriate
toolsandsealingcompounds(ensurepropane
resistant compounds are used in propane
applications).
FBK-250 Blower Kit
(See Figure 49 on page 25)-
All codes require a shut-off valve mounted
in the supply line. The orientation of the
shut-off valve should face the front. Figure
51 illustrates two methods for connecting the
gas supply. A sediment Trap is recommended
to prevent moisture and debris in the gas line
for damaging the valve.
An electrical outlet box is provided for the
installation of the FBK-250 forced air blower
kit. Electrical power must be provided to this
box to operate these blowers. Install the blower
kit according to the installation instructions
provided with the kit.
TEST ALL CONNECTIONS FOR GAS LEAKS
(FACTORY ANd FIELd):
Note: The tab connecting the receptacles of
the outlet box must be broken in FBK-100 and
FBK-200blowerkitapplications. SeeFigure50.
Step 6. WIRING - OPTIONAL FORCEd AIR
BLOWER KIT
WARNING
Never use an open flame to
check for leaks.
Step 7. CONNECTING GAS LINE
FBK-100 and FBK-200 Kits
Make gas line connections. All codes require a
shut-offvalvemountedinthesupplyline. Figure
51 illustrates two methods for connecting the
gas supply. The flex-line method is acceptable
in the U.S., however, Canadian requirements
vary depending on locality. Installation must
be in compliance with local codes.
(See Figure 48 on page 25) -
An electrical outlet box is provided for the
installation of the FBK-100, FBK-200 forced air
blower kits. Electrical power must be provided
to this box to operate these blowers. Install the
blowerkitsaccordingtotheinstallationinstruc-
tions provided with the kits.
26
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Subsequent lighting of the appliance will not
require such purging. Inspect the pilot flame
(remove logs, if necessary, handling carefully).
Optional Gas Flex Line Connector
3/8" NPT x 3/8"
Flare Fitting
1/2" x 3/8" Flare
Shut-Off Valve
Gas
Valve
Millivolt Appliance Checkout
The pilot flame should be steady, not lifting
or floating. Flame should be blue in color with
traces of orange at the outer edge.
3/8" Flex Tubing
Gas
Stub
The top 3/8" (10 mm) at the pilot generator
(thermopile) and the top 1/8" minimum (tip)
of the quick drop out thermocouple should be
engulfed in the pilot flame.
1/2" x 3/8"
Reducer
3/8" Nipple
3/8" Union
3/8" Close Nipple
The flame should project 1" (25 mm) beyond
the hood at all three ports (see Figure 53).
Replace logs if removed for pilot inspection.
3/8" Shut-Off Valve
Figure 51: Gas Connection
To light the burner; turn “ON” the remote wall
switch and rotate the gas valve control knob
counterclockwise to the “ON” position (“ON”
will be at the top side of the valve).
B. Brush all joints and connections with the gas
leak test solution to check for leaks. If bubbles
are formed, or gas odor is detected, turn the
gas control knob (off/pilot/on) to the “OFF”
position. Either tighten or refasten the leaking
connection, then retest as described above.
Hood Igniter Rod
MILLIVOLT
Thermocouple
SIT Gas Valve
C. When the gas lines are tested and leak free,
be sure to rinse off the leak testing solution.
3/8" Min
(9 mm)
Step 8. VERIFYING APPLIANCE
OPERATION
Pilot
Nozzels
With gas line installed, run initial system
checkout before closing up the front of the
unit. Follow the pilot lighting instructions
provided in the Care and Operation Instruc-
tions. For piezo igniter location on millivolt
appliances, see Figure 47 on Page 25.
Piezo
Ignitor
Thermopile
Figure 53
Millivolt Gas Valve Showing
Piezo Ignitor Location
Electronic Appliance Checkout
Note: lighting Instructions are also found on
the literature tag tied to the gas piping next
to the gas valve. To access the tag, open the
lower control compartment door (Figure 52)
by pushing in simultaneously the left and right
top corners of the door. (The door is hinged at
thebottom). Removethebottomcompartment
door by sliding the hinge pin, located at the
door’s left side, to the right until it disengages
from the left corner post hole.
Figure 52
To light the burner, turn ‘ON’ the unit-mounted
ON/OFF switch or the optional remote wall
switch. Ensure the igniter lights the pilot. The
pilotflameshouldengulftheflamerodasshown
in Figure 54.
Turn on gas supply and test for gas leaks, us-
ing a gas leak test solution (also referred to as
bubble leak solution).
Note: using a soapy water solution is an effec-
tiveleaktestsolutionbutitisnotrecommended,
because the soap residue that is left on the
pipes/fittings can result in corrosion over time.
ELECTRONIC
3/8 To 1/2 Inch
(9 mm to 13 mm)
Proper Flame
Adjustment
Pilot
When first lighting the appliance, it will take a
few minutes for the line to purge itself of air.
Once purging is complete, the pilot and burner
willlightandoperateasindicatedintheinstruc-
tion manual.
Nozzle
A. Light the appliance (refer to the lighting
instructionslabelinthecontrolcompartment
or in the Care and Operation Instructions
manual).
Ground
Electrode
Flame Rod
Hot Surface
Igniter
Figure 54
27
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Step 9. INSTALL VOLCANIC STONE,
GLOWING EMBERS ANd LOGS
Glowing Embers
NOTE: Turn off all electricity to the appliance
before you install volcanic stone, embers and
logs. DO NOT attempt to install the logs until
the appliance installation has been completed,
the gas line connected and tested for leaks and
theinitialburneroperationhasbeencheckedout.
Step 1. Remove the appliance front door (see
Removing Glass Encloslure panel on page 32.
Step 2. Install decorative volcanic stone -
Sprinklethedecorativevolcanicstoneinapleas-
ingpattern. Thevolcanicstoneshouldbeplaced
directly on top of the firebox bottom, along the
frontandtothebackattherightandleftsidesof
the burner. Position any optional ceramic fiber
liners before placing the stone. Logs should be
positioned after the volcanic stone.
Figure 56
Step 4. Placement of Logs -
All top logs that rest on lower logs, do so over
notches,indentsornubs. Properlogplacement
is critical to prevent sooting. Logs should be
placedinthegapsbetweentheflamepeaksand
should be positioned so they do not impinge
the flames.
WARNING
• dO NOT attempt to install the
logs until the appliance installa-
tion has been completed, the gas
lineconnectedandtestedforleaks
and the initial burner operation
has been checked out.
• The size and position of the log
set was engineered to give the
appliance a safe, reliable and
attractive flame pattern. Any
attempt to use a different log set
in the fireplace will void the war-
rantyandwillresultinincomplete
combustion, sooting, and poor
flame quality.
Note: This appliance is provided with enough
Glowing Embers for several applications, do
not feel compelled to use all that is in a new
bag. For best glowing effect, replace the ember
material annually. Replacement Glowing Em-
bers are available (Catalog Number 88l53).
Step5. Positiontheindividuallogsasshownin
Figures 57, 58 and 59. Logs should be placed
in the order shown. All logs that have notches
to fit over the grate tines should be positioned
with these notches directly against the grate.
Handle logs carefully to prevent breakage.
Glowing Embers
Separate into Quarter
Size (separate) Pieces
Proper log placement is critical to encourage
outstanding flame appearance and prevent
sooting. When positioned properly as shown,
logs will be positioned between flame peaks
and will not impinge any flames.
Bag of Glowing
Embers (rockwool)
Refer to Figure 57 for MPD-3328 Series ap-
pliances, to Figure 58 for MPD-3530 Series
appliances and to Figure 59 for MPD-4035
and MPD-4540 Series appliances.
• Logs get very hot and will
remainhotuptoonehouraftergas
supply is turned off. Handle only
when logs are cool. Turn off all
electricitytotheappliancebefore
you install grate, volcanic stone,
vermiculite, embers and logs.
• This appliance is not designed
toburnwood. Anyattempttodoso
couldcauseirreparabledamageto
theapplianceandprovehazardous
to your safety.
Figure 55
Step 3. Separate the Glowing Ember
(Rockwool) into pieces about the size of a
quarter (Figure 55 ). Keep the pieces fluffed
up, not matted. Distribute these pieces over
the front surface of the burner, as shown in
Figure 56. Do not use more than is neces-
sary. When properly positioned, the Glowing
Embers will cover approximately 65% of the
front burner and with no appreciable gaps or
openings. Ensure that the main burner ports
remain uncovered by the ember material.
REFERENCE
Firebox Accessories / Parts
Cat. No.
88L53
ModelNo.
description
FGE
Bag of Glowing Embers
Bag of decorative
Volcanic Stone
80L42
FdVS
• If logs are not installed
according to the log installation
instructions,flameimpingement
and improper combustion could
occur and result in soot and/or
excessive production of carbon
monoxide (CO), a colorless,
odorless, toxic gas.
28
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
MPd-3328 LOG PLACEMENT
Log
Number description (Stamped #)
1
1
2
3
4
5
6
Log, Rear (39-12)
Log, Left (39-1)
Log, Right (39-2)
3
Log, Top Center (39-13)
Log, Top/Left (39-3 )
Log, Top/Right (39-4)
2
Catalog Number for the entire log set: 24M15
Position the individual logs as shown below. Logs should be placed
in the order shown. Position the rear log on the brackets at the
rear of the firebox with the log's notches directly over the brackets.
Position the right log (log no. 3) by inserting the pin from the rear
log into the hole on its upper end. Place the left log and then the
smaller left and right top logs. All logs that have notches to fit over
the grate tines should be positioned with these notches directly
against the grate. All top logs that rest on lower logs, do so over
flattened mounting faces in the bottom logs.
4
6
5
Proper log and twig placement is critical to encourage outstanding
flame appearance and prevent sooting.
1
4
3
2
5
6
Figure 57
29
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
MPd-3530 LOG PLACEMENT
Log
Number description (Stamped #)
1
1
2
3
4
5
6
Log, Rear (39-5)
Log, Left (39-1)
3
Log, Right (39-2)
Log, Top Center (39-6)
Log, Top/Left (39-3)
Log, Top/Right (39-4)
2
Catalog Number for the entire log set: 24M22
Position the individual logs as shown below. Logs should be placed
in the order shown. Position the rear log on the brackets at the
rear of the firebox with the log's notches directly over the brackets.
Position the right log (log no. 3) by inserting the pin from the rear
log into the hole on its upper end. Place the left log and then the
smaller left and right top logs. All logs that have notches to fit over
the grate tines should be positioned with these notches directly
against the grate. All top logs that rest on lower logs, do so over
flattened mounting faces in the bottom logs.
4
6
5
Proper log and twig placement is critical to encourage outstanding
flame appearance and prevent sooting.
1
4
3
2
6
5
Figure 58
30
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
MPd-4035 ANd MPd-4540 LOG PLACEMENT
Log
Number description (Stamped #)
1
1
2
3
4
5
6
Log, Center (39-8)
Log, Rear (138)
Log, Right (39-10)
Log, Left (39-9)
2
3
Log, Top/Left (39-11)
Log, Top/Right (39-11)
Catalog Number for the entire log set: 24M25
Position the individual logs as shown below. Logs should be placed
in the order shown. Position the center log on the burner first, then
place the glowing embers as shown in Figure 56. Place the rear
log, both the right and left, and then the smaller left and right top
logs. All logs that have notches to fit over the grate tines should
be positioned with these notches directly against the grate. All top
logs that rest on lower logs, do so over flattened mounting faces
in the bottom logs.
4
5
6
Proper log and twig placement is critical to encourage outstanding
flame appearance and prevent sooting.
1
3
4
2
6
5
Figure 59
31
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Removing the Glass Enclosure Panel
(see Figure 60 )
Step 10. REMOVING ANd INSTALLING
THE GLASS dOOR
Step 11. BURNER AdjUSTMENTS
Flame Appearance and Sooting
Remove the top louver assembly or radiant
panel.
Proper flame appearance is a flame that is blue
at the base and becomes yellowish-orange in
the body of the flame.
WARNING
To access the glass door securing latches,
first open the lower control compartment door
(Figure 60) by pushing in simultaneously the
left and right top corners of the door (the door
is hinged at the bottom).
• donotattempttosubstitutethe
materialsusedonthesedoors,
or replace cracked or broken
glass.
When the appliance is first lit, the entire flame
may be blue and will gradually turn yellowish-
orangeduringthefirst15minutesofoperation.
If the flame remains blue, or if the flame is
orange with evidence of sooting (black tip), the
air shutter opening may need to be adjusted.
Remove the bottom compartment door by
sliding the hinge pin, located at the door’s left
side, to the right until it disengages from the
left corner post hole. Pull the door diagonally
to the left, away from the fireplace.
• Handlethisglasswithextreme
care! Glass is susceptible to
damage – do not scratch or
handleroughlywhilereinstall-
ing the glass door frame.
• The glass door(s) of this appli-
ance must only be replaced as
a complete unit as provided
by the manufacturer. do not
attempt to replace broken,
crackedorchippedglasssepa-
rately.
If the air shutter opening is closed too far,
sooting may develop. Sooting is indicated by
black puffs developing at the tips of very long
orangeflames. Sootingresultsinblackdeposits
forming on the logs, appliance inside surfaces
and on exterior surfaces adjacent to the vent
termination.
Locate the two (2) latches at the top of the
controlcompartmentanddisengagethemfrom
thedoorframebottomvee-flange,pullingdown
on their handles to open them.
Sooting is caused by incomplete combustion
in the flames and lack of combustion air enter-
ing the air shutter opening. To achieve a warm
yellowish-orange flame with an orange body
that does not soot, the shutter opening must be
adjusted between these two extremes.
Installing the Glass Enclosure Panel
(see Figure 60 )
Retrieve the glass door. Visually inspect the
gasket on the backside of the frame. Gasket
surface must be clean, free of irregularities
and seated firmly.
• do not attempt to touch the
frontenclosureglasswithyour
hands while the fireplace is in
use.
Position the door in front of the firebox opening
with the bottom of the door held away from the
fireplace (Figure 60 ). Hook the top flange of
thedoorframeoverthetopofthefireboxframe.
Air Shutter Adjustment Guidelines
• If there is smoke or soot present, first
check the log set positioning to ensure that
the flames are not impinging on any of the
logs. If the log set is properly positioned
and a sooting condition still exists, then the
air shutter opening should be increased.
WARNING
do not operate appliance with
theglassfrontremoved,cracked
or broken.
Let the bottom of the door frame swing gently
intowardsthefireplaceensuringthatthegasket
seats evenly as the door frame draws shut.
Fasten the two latches located underneath the
firebox floor to the door's vee-flange. Close
both the latches securely.
• Themoreoffsetsintheventsystem,thelarger
the air shutter opening will need to be.
• An appliance operated with the air shutter
opened too far, may have flames that appear
blue and transparent. These weak, blue and
transparent flames are termed anemic.
AVERTISSEMENT
Ne pas utiliser l'appareil si le
panneau frontal en verre n'est
pas en place, est craqué ou
brisé.
Lower Compartment Door and Hinge
• Propane models may exhibit flames which
candle or appear stringy. If this is present
and persists, adjust the air shutter to a more
closed position, then operate the appliance
for a few more minutes to ensure that the
flame normalizes and the flames do not
appear sooty.
Glass
Glass Door Frame
Door
Top Flange
Only doors certified with the appliance
shall be used.
Seules des portes certifiées pour cet
appareil doivent être utilisées.
The following chart is provided to aid you in
achieving the correct air shutter adjustment
for your installation.
CAUTION: dO NOT abuse glass door by
striking or slamming shut.
Air Shutter Adjustment Guidelines
Amount of
Primary Air
Flame
Color
Air Shutter
Adjustment
If air shutter is
closed too far
Flame will Air shutter
be orange gap should be
increased
Glass Door Frame
Bottom Vee-flange
If air shutter is
open too far
Flame will Air shutter
be blue gap should be
decreased
Firebox Floor
Figure 60
32
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
WARNINGS
• Airshutteradjustmentshould
only be performed by a quali-
fiedprofessionalservicetech-
nician.
• Ensure front glass panel are
in place and sealed during
adjustment.
CAUTIONS
• Soot will be produced if the
airshutterisclosedtoomuch.
Any damage due to sooting,
resulting from improperly
setting the air shutter, is not
covered under the warranty.
• The air shutter door and
nearby appliance surfaces
are hot. Exercise caution to
avoid injury while adjusting
flame appearance.
Figure 61
MPd-3328 MOdEL
1. Refer to Figures 61, 62 and 63 for proper
flameappearance. Toadjusttheflame,rotate
theadjustmentrod towardthebackortoward
the front of the fireplace (rod located in the
lower control area). Position the air shutter
to the factory setting as shown in the table
in Figure 64.
Figure 62
MPd-3530 MOdEL
2. Light appliance (follow lighting procedure
on lighting label in control compartment or
in the Care and Operation Instructions).
3. Allow the burner to operate for at least 15
minutes while observing the flame continu-
ously to ensure that the proper flame ap-
pearancehasbeenachieved. Ifthefollowing
conditions are present, adjust accordingly.
•
If flame appears weak or sooty, adjust
the air shutter, incrementally, to a more
open position until the proper flame
appearance is achieved.
•
If flame remains blue, adjust the air
shutter, incrementally, to a more closed
position until the proper flame appear-
ance is achieved.
Figure 63
MPd-4035 ANd MPd-4540 MOdEL
4. Leave the control knob (OFF/PILOT/ON)
in the ON position and the burner ON/OFF
switch (and remote switches, if applicable)
in the OFF postion.
5. When satisfied that the burner flame appear-
ance is normal, reinstall the lower control
compartment door, then proceed to finish
the installation.
33
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Step 12. HOOd INSTALLATION
Combustible
Adjusting Set Screw
Finished Wall
This area must remain
clear of combustible
materials.
Refer to Figures 65 and 66. All models must
have hoods installed prior to operating.
Materials
Adjustment Rod Up
(Fully Open Position)
Burner Tube
Air Shutter
Min. 1"
Onallcleanfaceunits, slidethehoodintotheslots
ontheloweredgeoftheradiantpanel(Figure 65).
Combustible
material may
touch top of
appliance.
(25 mm)
Onlouveredfaceunits,slidethehoodintotheslots
on the lower edge of the cabinet top (Figure 66).
Header
Adjustment Rod Down
(minimum air
opening position)
Spacing
Top Standoff
Combustible
materials
FINISHING REQUIREMENTS
NOT allowed
below this point
on face
Top of Appliance
Radiant panel
Top of Door Frame
FACTORY AIR
SHUTTER
SETTING
inches (mm)
1/32 (O.8)
3/16 (4.76)
1/32 (O.8)
3/16 (4.76)
1/32 (O.8)
Wall details
of appliance.
Gas
Type
Models
Complete finished interior wall. To install the
appliance facing flush with the finished wall,
position framework to accommodate the thick-
ness of the finished wall (Figures 65 and 66 )
Hood must be installed as shown.
Nat.
Prop.
Nat.
Prop.
Nat.
Prop.
Nat.
Prop.
Nat.
Clean Face Models
MPDT-3328
MPDR-3328
MPD-3530
MPD-4035
MPD-4540
Figure 65
See Page 5 for
Cold Climate Insulation and
Page 8 for Clearances.
Combustible
Finished Wall
Materials
3/16 (4.76)
This area must remain
clear of combustible
materials.
1/8 (3.2)
1/2 (13)
1/8 (3.2)
1/2 (13)
Min. 1"
(25 mm)
Prop.
Combustible
material may
touch top of
appliance.
Figure 64
Header
Spacing
Top Standoff
Combustible
materials
NOT allowed
below this point
on face
Top of Appliance
Louvers
of appliance.
Top of Door Frame
Hood must be installed as shown.
Louver Face Models
Figure 66
34
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
STEP 13. ATTACHING SAFETY-IN-OPERATION WARNINGS
It is the installer’s responsibility to ensure these warnings are properly affixed during installation. These warning labels are a
critical step in informing consumers of safe operation of this appliance.
ATTACHING SAFETY-IN-OPERATION
WARNINGS
APPOSITION dES MISES EN GARdE RELATIVES COLOCACIóNdEAdVERTENCIASdESEGURIdAd
à LA SéCURITé d’UTILISATION EN OPERACIóN
It is required that the safety instruction labels
furnished with the fireplace be affixed to the op-
eration and control point of the fireplace. A safety
instruction label must be affixed to the wall switch
plate where the fireplace is turned on and off (See
Figure A) or wall thermostat (See Figure B) and if
used on the remote control handheld transmitter
(Figure C). To properly complete the installation of
thisfireplace,locatethemulti-lingualadhesivelabels
provided with the Care and Operation Instructions
and proceed as follows:
Il est impératif que les étiquettes de sécurité fournies Se requiere que las etiquetas de instrucciones de
avec le foyer soient collées à côté des dispositifs seguridad incluidas con la chimenea se coloquen en
de contrôle du foyer. Une étiquette de sécurité doit el punto de operación y control de la misma. Se debe
être collée sur la plaque de l’interrupteur contrôlant colocar una etiqueta de instrucciones de seguridad
l’allumagedufoyer(voirFigureA)ousurlethermostat en la placa del interruptor de pared desde el cual se
mural (voir Figure B) et, le cas échéant, sur le boîtier enciendeyseapagalachimenea(verlaFiguraA)oenel
delatélécommande(FigureC). Pouracheverl’instal- termostatodepared(verlaFiguraB)yeneltransmisor
lationcorrectedecefoyer, procédezcommesuitavec decontrolremoto(FiguraC)siseusa. Paracompletar
lesétiquettesadhésivesenlanguesétrangèresfournies correctamente la instalación de esta chimenea,
avec les instructions d’utilisation et d’entretien :
encuentrelasetiquetasadhesivasmultilingüesincluidas
con las instrucciones de cuidado y operación y haga
lo siguiente:
1. Repérez l’interrupteur ou le thermostat mural qui
contrôle le foyer (vérifiez que l’interrupteur
1. Locate the wall switch or wall thermostat that
controlsthefireplace(verifytheswitchoperates
the fireplace by turning it on and off). Clean the
wall switch plate or wall thermostat thoroughly
to remove any dust and oils. Affix the label to
the surface of the plate of the wall switch that
controls the fireplace (Figure A) or the wall
thermostat (Figure B). Choose the language
primarily spoken in the home. If unknown, affix
the English language label.
contrôle le fonctionnement du foyer en le faisant 1. Identifique el interruptor o el termostato de pared
basculerdeMarcheàArrêt,etvice-versa).Nettoyez
soigneusement la plaque murale de l’interrupteur
ou le thermostat mural pour éliminer la poussière
et les traces de graisse ou d’huile. Collez l’étiquette
sur la surface de la plaque de l’interrupteur mural
qui contrôle le foyer (Figure A) ou du thermostat
mural (Figure B). Choisissez la langue qui est
principalement parlée dans la résidence du
propriétaire. En cas de doute, collez l’étiquette en
anglais.
quecontrolalachimenea(verifiquequeelinterruptor
opera la chimenea encendiéndola y apagándola).
Limpie bien la placa del interruptor o el termostato
de pared para quitar el polvo y aceite. Pegue la
etiquetaenlasuperficiedelaplacadelinterruptorque
controla la chimenea (Figura A) o en el termostato
de pared (Figura B). Seleccione el idioma que
más se habla en la casa. Si no sabe cuál es, use la
etiqueta en inglés.
2. Ifaremotecontrolisusedtocontrolthefireplace,
locate the transmitter and clean it thoroughly
to remove any dust and oils. Affix the label to
the surface of handheld transmitter (Figure C).
Choose the language primarily spoken in the
home. If unknown, affix the English language
label.
2. Si se usa un control remoto para controlar la
chimenea, encuentre el transmisor y límpielo bien
para quitar el polvo y aceite. Pegue la etiqueta en
la superficie del transmisor (Figura C). Seleccione
el idioma que más se habla en la casa. Si no sabe
cuál es, use la etiqueta en inglés.
2. Si une télécommande est utilisée pour contrôler
le foyer, nettoyez la soigneusement pour éliminer
la poussière et les traces de graisse ou d’huile.
Collez l’étiquette sur le boîtier de la télé-
commande (FigureC).Choisissezlalanguequiest
principalementparléedanslarésidenceduproprié- 3. Sinopuedeencontrarlasetiquetas,sírvasellamara
taire. En cas de doute, collez l’étiquette en anglais.
3. Si vous ne trouvez pas les étiquettes, veuillez
appelerLennoxHearthProductsouvotredistribu-
teur Lennox Hearth Products local pour recevoir
gratuitement des étiquettes supplémentaires.
LennoxHearthProductsoaldistribuidordeLennox
HearthProductsmáscercanopararecibiretiquetas
deinstruccionesdeseguridadadicionalesgratuitas.
3. If you are unable to locate the labels, please call
LennoxHearthProductsoryournearestLennox
Hearth Products dealer to receive additional
safety instruction labels free of charge.
Juego de etiquetas de repuesto - Nº de cat. H8024
Cat. No. H8024 Replacement Label Kit
LENNOX HEARTH PROdUCTS
Étiquettes de remplacement, n° cat. H8024
1-800-9-LENNOX
LENNOX HEARTH PROdUCTS
1-800-9-LENNOX
LENNOX HEARTH PROdUCTS
1-800-9-LENNOX
Nota: La etiqueta en inglés es transparente con texto
rojo. Las etiquetas en francés y español son negras
con texto blanco.
Note: English is red text on clear label. French and
Spanish are white text on black label.
Remarque : Le texte anglais est rouge sur un support
transparent. Le texte français et espagnol est blanc
sur un support noir.
SAFETY LABEL
dIAGRAMS
dIAGRAMMES dES éTIQUETTES
dIAGRAMAS dE ETIQUETAS
dE SéCURITé
dE SEGURIdAd
Figure A
Figure B
Figure C
35
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
INSTALLATION ACCESSORIES
Listed Secure Vent™ Components
Listed Secure Vent™ Components
Cat. No.
Model
description
Cat. No.
77L70
77L71
77L72
77L73
77L74
77L75
Model
SV4.5L6
SV4.5L12
SV4.5L24
SV4.5L36
SV4.5L48
SV4.5LA
description
6 Inch (152 mm)
12 Inch (305 mm)
24 Inch (610 mm)
36 Inch (914 mm)
48 Inch (1219 mm)
H1968
SV4.5HT-2
Horizontal Square
Termination with
Firestop/ Spacer (H2246)
and Adaptor (74L61)
Vent Sections
(Rigid)
H2152
SV4.5CGV-1 Vertical Termination Cap,
High Wind
Telescopic Length Slip
Section (2" to 7-1/2" rigid)
77L76
77L77
SV4.5E45
SV4.5E90
45 Degree Elbow
H4687
H4716
H4717
94L10*
SV4.5CTS
Chase Top Termination,
Square
(Ref. Instr. #750207M)
SV4.5CTS-B Chase Top Termination,
90 Degree Elbow
Square, Black
(Ref. Instr. #750207M)
10K81
89L40
SFMP
Mill-Pac, Black, High-
Temperature Sealant
SV4.5CTS-TC Chase Top Termination,
S
e
a
l
a
Square, Terra Cotta
(Ref. Instr. #750207M)
n
t
SFMP-12
Mill-Pac, Black, High-
Temperature Sealant,
Bulk 12 pack
SV4.5HTSS
Horizontal Small Square
Termination with
Firestop/Spacer (96K80)
and Adapter (74L61)
99L02
99L03
96K93
SV4.5HRK14 Horizontal Riser Kit, 14",
(Ref. Instr. #750146M)
98L27*
SV4.5HTSSL Horizontal Small Square-
Long Termination with
SV4.5HRK36 Horizontal Riser Kit, 36",
(Ref. Instr. #750146M)
Firestop/Spacer (96K80)
and Adapter (74L61)
SV4.5SU
Support Strap
17M52
17M53
87L02
SV4.5HGS-1 Termination Guard,
Square (1 pack)
(Ref. Instr. #750109M)
H5816
SV4.5-
Through Wall Shield Kit
(used to shield the
direct-vent pipe from
blown insulation)
TWSK10
SV4.5HGS-12 Termination Guard, Hori-
zontal Square (12 pack)
(Ref. Instr. #750109M)
(Ref. Instr. #750247M)
SV4.5HGS
Termination Guard for
Horizontal Square Termi-
nation (Deluxe) (1 pack)
(Ref. Instr. #750055M)
The following flashings come packaged with a storm collar:
77L78
77L79
SV4.5F
Flat Roof Flashing
SV4.5FA
1/12 to 7/12 Adjustable
Flashing
H5820
SV4.5HTSK
Termination Shroud
(Guard) for Horizontal
Square Termination
(1 pack)
77L80
77L81
SV4.5FB
7/12 to 12/12 Adjustable
Flashing
(Ref. Instr. #750246M)
SV4.5SC6
Storm Collar (6 per box)
H3907
H1988
H1985
H1987
H1986
SV4.5ARSA Attic Insulation Shield w/
adjustable height, 12"-22"
H6183
H6184
H2246
SV4.5HF5
SF4.5HF5
Firestop Spacer, 5", rigid
Firestop Spacer, 5", flex
CTSA-33
CTSO-33
CTSO-44
CTSO-46
Chase Top Shroud Kit,
Arch Top 3 X 3 Ft.,
(Ref. Instr. #750194M)
SV4.5HF-10 Firestop/Spacer-Horizon-
tal, rigid (3-1-1 spacing),
10 Pack
H2247
96K92
SV4.5VF-10 Firestop/Spacer-Vertical,
rigid (1-1-1 spacing),
10 Pack
Chase Top Shroud Kit,
Open Top 3 X 3 Ft.,
(Ref. Instr. #750193M)
SV4.5SP
Support Plate
Chase Top Shroud Kit,
Open Top 4 X 4 Ft.,
(Ref. Instr. #750193M)
Chase Top Shroud Kit,
Open Top 4 X 6 Ft.,
(Ref. Instr. #750193M)
*Only for use with MPdT/R-3328 and MPd-3530 models.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
36
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
INSTALLATION ACCESSORIES CONTINUEd
Listed Secure Flex™ Components
Cat. # Model description
Listed Secure Flex™ Components
Cat. #
Model
description
These termination kits include firestop/spacer, gear clamps and flex adaptor.
H1969
SF4.5HT-2 Horizontal Square Termina-
tion for flex (without flex
vent)
60L10
98K03
H2248
SF-18
SF-12
18 feet (5.49 m) *
compressed flex
(Ref. Instr. #750053M)
77L87
77L88
77L89
77L90
77L91
SFKIT12S Square Term. for flex
(with 12 inch [305 mm]
12 feet (3.66 m)*
compressed flex
(Ref. Instr. #750052M)
compressed flex vent**)
SFKIT18S Square Term. for flex
(with 18 inch [457 mm]
SF4.5HF-10 Firestop / Spacer -
Horizontal, flex (3-1-1
compressed flex vent**)
SFKIT24S Square Term. for flex
(with 24 inch [610 mm]
spacing), 10 Pack
H2249
56L74
SF4.5VF-10 Firestop/Spacer-Vertical,
compressed flex vent**)
flex (1-1-1 spacing), 10 Pk
SFKIT36S Square Term. for flex
(with 36 inch [914 mm]
SFVT30
SFVT45
Vertical Termination for flex
(flatto6/12)withflexadaptor,
section of rigid vent, roof
supportcollarassembly,roof
flashing and storm collar.
(Ref. Instr. #750052M)
compressed flex vent**)
SFKIT48S Square Term. for flex
(with 48 inch [1219 mm]
compressed flex vent**)
56L75
Vertical Termination for flex
(6/12 to 12/12) with flex
adaptor, section of rigid
vent, roof support collar
assembly, roof flashing,
and storm collar.
94L04* SFKIT12SS Small Square Termination for
flex, with 12 in. (305 mm) of
compressed flex vent**
(Ref. Instr. #750204M)
94L05* SFKIT18SS Small Square Termination for
flex, with 18 in. (457 mm) of
compressed flex vent**
(Ref. Instr. #750052M)
(Ref. Instr. #750204M)
91L66
91L67
H7748
SFGC4-6
SFGC7-6
H7748
GearClamp4.5in.(114mm)
for flex (6 pack)
94L06* SFKIT24SS Small Square Termination for
flex, with 24 in. (610 mm) of
compressed flex vent**
Gear Clamp 7.5 in. (190.5
mm) for flex (6 pack)
(Ref. Instr. #750204M)
36" Flex Connector
Kit. 36" of flex with two
adapters for mating two
rigid sections of vent
together.
94L07* SFKIT36SS Small Square Termination for
flex, with 36 in. (914 mm) of
compressed flex vent**
(Ref. Instr. #750204M)
94L08* SFKIT48SS Small Square Termination for
flex, with 48 in. (1219 mm)
of compressed flex vent**
(Ref. Instr. #750204M)
94L09*
SF-HTSS
Horizontal Small Square
Termination for flex, without
flex vent (Ref. Instr. #750204M)
*Only for use with MPdT/R-3328 and MPd-3530 models.
**All compressed flex vents can be expanded up to two times.
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
37
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
GAS CONVERSION KITS
Electronic HONEYWELL Systems
Natural Gas To Propane Gas
Conversion Kits
WARNING
Models
MPdT/R-3328
MPd-3530
MPd-4035
MPd-4540
Catalog No.
26M59
This conversion kit shall be installed by a qualified service agency in
accordance with the manufacturer’s instructions and all applicable codes
andrequirementsoftheauthorityhavingjurisdiction. Iftheinformationin
these instruction is not followed exactly, a fire, explosion or production of
carbon monoxide may result causing property damage, personal injury
or loss of life. The qualified service agency is responsible for the proper
installationofthiskit. Theinstallationisnotproperandcompleteuntilthe
operationof theconverted appliance is checked as specified in the manu-
facturer’s instructions supplied with the kit.The qualified service agency
performing this installation assumes responsibility for this conversion.
26M60
26M61
26M62
Electronic HONEYWELL Systems
Propane Gas To Natural Gas
Conversion Kits
Models
MPdT/R-3328
MPd-3530
MPd-4035
MPd-4540
Catalog No.
26M63
AVERTISSEMENT
26M64
26M65
Cette trousse de conversion doit être installée par un technicien agréé,
selonlesinstructionsdufabricantetselontouteslesexigencesettousles
codes pertinents de l’autorité compétente. Assurez-vous de bien suivre
les instructions dans cette notice pour réduire au minimum le risque
d’incendie,d’explosionoulaproductiondemonoxydedecarbonepouvant
causer des dommages matériels, des blessures ou la mort. Le tecnicien
agrééestresponsabledel’installationdecettetrousse.L’installationn’est
pas adéquate ni complète tant que le bon fonctionnement de l’appareil
convertin’apasétévérifiéselonlesinstructionsdufabricantfourniesavec
la trousse. Le fournisseur de service qualifié ayant réalisé l'installation
assume les responsabilités liées à la conversion.
26M66
INSTALLATION INSTRUCTIONS
Step 1. TURN OFF THE GAS SUPPLY TO THE
APPLIANCE and disconnect power supply at the
circuit breaker. Ensure appliance is cold.
CAUTION: THE GAS SUPPLY SHALL BE
SHUT OFF PRIOR TO dISCONNECTING THE
ELECTRICAL POWER, BEFORE PROCEEd-
ING WITH THE CONVERSION.
In Canada:
THE CONVERSION SHALL BE CAR-
Millivolt SIT Systems
ATTENTION: AVANT d’EFFECTUER
LA CONVERSION, COUPEZ d’ABORd
L’ALIMENTATION EN GAZ, ENSUITE,
COUPEZ L’ALIMENTATION éLECTRIQUE.
Natural Gas To Propane Gas
RIEd OUT IN ACCORdANCE WITH THE
REQUIREMENTS OF THE PROVINCIAL
AUTHORITIES HAVING jURISdICTION
ANd IN ACCORdANCE WITH THE RE-
QUIREMENTS OF THE CAN/CSA-B149.1
INSTALLATION COdE.
Conversion Kits
Models
Catalog No.
H2009
MPdT/R-3328
MPd-3530
MPd-4035
MPd-4540
H2011
Open the bottom drop-down door. Open it (see
Figure52 onpage27)bypushinginsimultane-
ously the left and right top corners of the door.
(The door is hinged at the bottom.) Remove the
bottom compartment door by sliding the hinge
pin, located at the door’s left side, to the right
until it disengages from the left corner post
hole. Pull the door diagonally to the left, away
from the fireplace.
H2013
H2015
LA CONVERSION dEVRA êTRE EF-
FECTUéE CONFORMéMENT AUX RE-
COMMANdATIONS dES AUTORITéS
PROVINCIALES AYANT jURIdICTION ET
CONFORMéMENT AUX EXIGENCES dU
COdEd'INSTALLATIONCAN/CSA-B149.1.
Millivolt SIT Systems
Propane Gas to Natural Gas
Conversion Kits
Models
MPdT/R-3328
MPd-3530
MPd-4035
MPd-4540
Catalog No.
Remove the front glass door/frame from the
appliance.
H2010
H2012
H2014
H2016
Gas conversion kits are available to adapt your
appliance from the use of one type of gas to
the use of another. These kits contain all the
necessarycomponentsneededtocompletethe
task including labeling that must be affixed to
ensure safe operation.
Kitpartnumbersarelistedhere andthefollow-
ingstepsdetailtheconversionprocedure. Refer
totheinstructionsprovidedwiththeconversion
kit when performing any gas conversion.
38
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Millivolt Appliances
Electronic Appliances
Step 2. Carefully remove the logs. Exercise
Step 4. SIT Systems - Refer to Figure 68 and
the instructions provided with the kit. Using a
TorxT20,removeanddiscardthethreepressure
regulator mounting screws. Remove the pres-
sure regulator, spring, poppet, diaphragm and
bushing. discard all removed components.
Ensuretherubbergasketinstalledonthebackof
the replacement pressure regulator is properly
positionedandinstallthenewpressureregula-
tor using the new screws supplied with the kit.
Tighten screws to 25 In. lb. torque.
care so as not to break the logs.
Step 7. Honeywell Electronic Valves - See
Figure 70 and the instructions provided with
the kit. Remove the slotted cap screw, o-ring,
pressure-regulatingadjustingscrewandspring.
Retain all parts for possible later use. Install
new components from the kit. Black cap and
red spring for propane gas units. Silver cap
and stainless steel spring for natural gas units.
Before installing the cap, attach manometer to
themanifoldsidepressuretestfittingandadjust
screw until pressure reads 3.5 inches water
column (0.87 kPa) for natural gas, and 10.0
incheswatercolumn(2.49kPa)forpropanegas.
Step 3. Refer to Figure 67.
A. Above the burner, remove the two baffle
securing screws. Remove the baffle.
B. Remove the two screws securing the trap-
ezoidal plate to the burner. Remove the plate.
C. Remove the burner assembly with attached
venturi tube.
Burner Assembly
Pressure
Regulator
Inlet Pressure Test Port
Manifold
Pressure
Test Port
Remove
These
Components
Gas Valve
Assembly
Figure 68
Slotted
Cap
Spring
Step 5. Attach manometer to the manifold side
pressure test fitting and verify manifold pres-
sure reads 3.5 inches water column (0.87 kPa)
for natural gas, and 10.0 inches water column
(2.49 kPa) for propane gas.
Adjusting
Screw
Figure 70
Orifice
Step 6. Refer to Figure 69 and remove the
pilot hood assembly to access the hexed pilot
orifice. Remove and replace the orifice with
the one provided with the kit.
Figure 67
Pilot
Orifice
Figure 69
39
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
See Figure 71 and replace the pilot orifice as
All Models
follows: Remove the ignitor assembly retainer
clip, and carefully remove the ignitor assembly.
Use pipe joint compound or Teflon tape on all
pipefittingsbeforeinstalling(ensurepropane
resistant compounds are used in propane ap-
plications, do not use pipe joint compounds
on flare fittings).
Exercise extreme care to prevent damage to
or breakage of the ignitor assembly. Remove
the screw securing the pilot assembly to its
mounting bracket. Back off the flare nut at
the end of the pilot gas line to free the pilot
assembly from the gas line. Remove the pilot
orifice and replace it with the one provided with
the conversion kit. Reinstall the pilot assembly
by reversing the steps detailed here.
Figure 72
Step 8. (Refer to Figure 67 on page 39 )
A. Remove the orifice from the manifold and
replace it with the one provided in the kit. See
the following table for orifice sizes for natural
and propane models. Figure 72 illustrates
the orifice.
Step9.Reassembletheremainingcomponents
by reversing the procedures outlined in the
preceding steps.
Step 10. Attach the conversion label provided
in the conversion kit next to the rating plate on
the appliance.
When reinstalling the ignitor assembly, use
extreme care to prevent damage and break-
age. do not apply any leverage to the ignitor
assembly while restoring the retainer clip to
its original position.
B. Retrievetheburnerandholdtheventuritube
above the orifice . Place the shutter adjusting
rod in the propane slot of the shutter arm (see
Figure 64 on page 34 ). Set the burner assem-
bly into its position and secure the trapezoidal
plate with the two screws previously removed.
Step 11. Turn on gas supply and test for gas
leaks (refer to page 27).
Pilot
Pilot
Assembly
C. Reinstall the baffle with the two baffle
Orifice
securing screws.
Ignitor
Assembly
Burner Orifice Sizes
Elevation 0-4500 feet ( 0-1372 meters)
Model
Series
Nat.Gas
drill size (inches)
Propane
drill size (inches)
#45 (0.0820")*
39L66•
0.048 inch
99K78•
MPdT-3328
MPdR-3328
Retaining
Clip
Flare Nut
#44 (0.0860")*
#55 (0.0520")*
19L52•
MPd-3530
60j80•
Note: If the ignitor is damaged, a replacement
kit is available, order Catalog Number 87l54.
#37 (0.1040")*
24M10•
0.063 inch
21L01•
MPd-4035
#36 (0.1065")*
18L40•
#52 (0.0635")*
37G00•
Figure 71
MPd-4540
* Standard size installed at factory
• Part /Cat. Number
Table 9
40
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
NOTES
41
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LENNOX HEARTH PRODUCTS • MERIT® PLUS DIRECT VENT GAS FIREPLACES (MPD33/35/40/45) • INSTALLATION INSTRUCTIONS
Lennox Hearth Products reserves the right to make changes at any time, without notice, in design,
materials, specifications, and prices, and also to discontinue colors, styles, and products.
Consult your local distributor for fireplace code information.
Printed in U.S.A. © 2002/2011 Lennox Hearth Products
1508 Elm Hill Pike, Suite 108 • Nashville, TN 37210
P/N 850014M Rev. V 08/2011
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