L7224A,C; L7248A,C,L
Oil and Electric Boiler
®
Electronic Aquastat Controllers
INSTALLATION INSTRUCTIONS
IMPORTANT
APPLICATION
Use of Outdoor Temperature Reset on a tank-
less coil application requiring a Low Limit setting
will result in reduced system effectiveness and
efficiency.
The L7224A,C and L7248A,C,L 2012 Compliant
®
Electronic Aquastat Controllers provide electronic
temperature sensing in a UL limit-rated control with a
single sensing probe. The L7224A,C and L7248A,C,L
control the circulator, oil or electric burner or contactor,
and boiler temperature. The L7224/L7248 is “Outdoor
Temperature Reset” ready which is enabled when
connected to the W8735Y1000 wireless or W8735S1000
wired Outdoor Reset Kit. Outdoor Reset with the L7224/
L7248 is intended for all applications except for tankless
coil systems for domestic hot water. Compliance to 2012
DOE regulation ensures efficiency is maximized without
interfering with domestic hot water demand.
SPECIFICATIONS
Electrical Ratings:
Voltage: 120 Vac, 60 Hz.
Power: 7 VA maximum at 120 Vac plus external loads.
Thermostat current: 100 mA nominal at 24 Vac.
Burner Relay:
7.4 A at 120 Vac Full Load Amperage (FLA);
44.4 A inrush Locked Rotor Amperage (LRA);
Less Ignition Load: 360 VA.
The L7224A,C and L7248A,C,L replace the L8124A,
L8124C, L7124A,C, L7148A and L8148A Controllers.
The L7224A,C and L7248A,C,L series controls provide
status and diagnostic information through an LED display
combined with LED lights as well as EnviraCOM™
communications enabled thermostats and diagnostic
tools to enhance the diagnostic process.
Circulator Relay:
7.4 A at 120 Vac FLA; 44.4 A inrush LRA.
Zone Controller (ZC): 7.4 A at 120 Vac FLA;
44.4 A inrush LRA.
NOTE: All loads combined cannot exceed 2000 VA.
Environmental Ratings:
Temperature: -30 °F to +150 °F (-34 °C to +66 °C).
Humidity: 0 to 95% relative humidity, noncondensing.
L7224/L7248 Aquastat Controllers are intended for use
in residential-type applications.
Approvals:
Underwriters Laboratories Inc. Component Recognized.
Canadian Underwriters Laboratories Inc. Component
Recognized.
2012 DOE Compliance and Operation
Operation of this control may delay the burner operation while the residual heat is
circulated out of the boiler.
®
NOTE: This operation may be different than earlier electronic Aquastat
revisions which did not implement thermal purge.
68-0281-16
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L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS
New Installation
SENSOR WIRES
CONTROLLER CASE
Order well assemblies separately; see Table 1 and form
no. 68-0040, Immersion Wells and Compression Fittings
for Temperature Controllers. Boilers usually have tappings
that allow the well to be mounted horizontally so boiler
water of average temperature can circulate freely over the
well.
BOILER
IMMERSION
WELL
SENSOR
1. Turn off all power and drain the boiler, if applicable.
2. If no tapping is provided, prepare properly sized and
threaded tapping near the top of the boiler.
3. Sparingly coat the well threads with pipe dope.
HEAT-CONDUCTIVE COMPOUND
(OPTIONAL)
NOTE: Do not attempt to tighten by using the case
as a handle.
IMMERSION
WELL CLAMP
M16120
4. Install the well in the boiler tapping and tighten
securely.
IMMERSION WELL
CLAMP SCREW
5. Refill boiler and check for water leakage.
6. Loosen but do not remove the well clamp screw.
7. Fit the case into the well so the clamp on the case
slides over the flange on the well.
Fig. 2. Position of sensor in immersion well.
8. Securely tighten the clamp screw.
9. Insert the sensor element into the well until it bot-
toms. See Replacement Sensor Installation section
for details. (If necessary, slightly bend the wire
inside the case to hold the sensor against the bot-
tom of the well.)
Flush-Mounted Aquastat
Replacement
Turn off all power and remove the old control. Refer to the
cover insert of the old control to identify and tag each
external lead as it is disconnected. If the old well is
unsuitable for the new installation, remove it and replace it
with a suitable new well. If the old well is suitable, use it.
10. Turn power ON.
11. Set High Limit, Low Limit and Low Limit Differential
to the settings recommended by the boiler OEM.
(See OPERATION section.) (See INSTALLATION
steps 6 and 7.)
Well-Mounted Aquastat
Replacement
12. On L7248L models, adjust ELL option to match your
configuration (see OPERATION section, and Fig. 11
and 13).
Turn off all power and remove the old control. Refer to the
cover insert of the old control to identify and tag each
external lead as it is disconnected. If the old well is
unsuitable for the new installation, remove it and proceed
with instructions for new installation. If the old well is
suitable, use it.
IMPORTANT
Best thermal response is obtained with a well
that snugly fits the sensor. Insert the sensor until
it rests against the bottom of the well. Use a well
of correct length and bend the wiring, if neces-
sary, to hold the bulb against the bottom of the
well.
1. Loosen, but do not remove, the well clamp screw on
the side of the control case.
2. Position immersion well clamp snugly over the
flange of the adapter and tighten the clamp screw.
3. Insert the sensor into the well as shown in Fig. 2 or
3. (See Replacement Sensor Installation section for
details.)
If the well is not a snug fit on the sensor, use the
heat-conductive compound (furnished with
TRADELINE models) as follows: Fold the
®
plastic bag of compound lengthwise and twist it
gently. Then snip off end of bag and work the
open end of the bag all the way into the well.
Slowly pull out the bag while squeezing it firmly
to distribute compound evenly in the well. Bend
the wiring, if necessary, to hold the sensor
against the bottom of the well and to hold outer
end of the sensor in firm contact with the side of
the well. See Fig. 2. Wipe excess compound
from the outer end of the well.
THERMOSTAT
TERMINALS
DISPLAY
FUSE
L I N E
ENVIRACOMTM
TERMINALS
SENSOR
SENSOR HOLES
CONNECTOR
M32186
Fig. 3. Circuit board, showing sensor connection and
well holes for horizontal mount models.
3
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L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS
WIRING
SENSOR WIRES
BOILER
WARNING
Electrical Shock Hazard.
Can cause serious injury or death.
Disconnect power supply before making wiring
connections to prevent electrical shock or
equipment damage.
IMMERSION
WELL
SENSOR
HEAT-CONDUCTIVE COMPOUND
(OPTIONAL)
All wiring must comply with local electrical codes and
ordinances. Do not exceed the specifications in the
Application section when wiring this control. Use wire
rated for 194 °F (90 °C) or higher.
M22026
Fig. 4. Replacement sensor installation.
IMPORTANT
The terminals on these Aquastat Controllers are
approved for use with copper wire only.
Replacement Sensor Installation
Follow the appropriate wiring diagrams shown on the
inside of the front cover of the L7224A,C; L7248A,C,L or
in Fig. 8–13.
Turn off all power and:
1. Carefully disconnect sensor from circuit board by
pulling gently on the connector.
2. Gently pull sensor from thermo well and through cir-
cuit board by pulling on leadwires.
3. Carefully align replacement sensor with hole in cir-
cuit board and guide through Aquastat case and
into well. (See Fig. 5).
Refer to Fig. 6 for Connections for the optional Outdoor
Reset Module and the Domestic Hot Water (DHW)
module. In subsequent wiring diagrams these modules
will be displayed with a dotted line signifying that they are
optional.
4. Make sure sensor is fully seated to bottom of well
(See Fig. 4). Use a small pencil to measure depth of
sensor in well, if necessary.
5. Connect sensor to circuit board by pressing con-
nector on sensor unit into mating connector on cir-
cuit board (See Fig. 5).
6. For remote sensors (flush-mounted Aquastat Con-
trollers) be sure to use 121571AA Clamp (see
Accessories) to securely hold sensor in place.
W8735Y1000 OR W8735S1000
OUTDOOR RESET MODULE
(W8735S1000 SHOWN)
1
2
3 OT OT
T
T
3
2
1
C7089U1006
OUTDOOR
SENSOR
ENVIRACOMTM
THERMOSTAT
TERMINALS
TERMINALS
ZR
L1
W8735S1008
DOMESTIC HOT
WATER MODULE
T
L2
T
3
2
1
C2
B2
C1
B1
ZC
1
2
3 TS TS
DISPLAY
32003971-003
TEMPERATURE
SENSOR
ZR
L1
M34961
SENSOR
L2
CONNECTOR
Fig. 6. Wiring the Outdoor Reset Module and the
Domestic Hot Water Module.
RELAYS
C2
B2
C1
B1
ZC
OPERATION
SENSOR HOLES
FUSE
General
M32187
The L7224A,C and L7248A,C,L Oil Electronic Aquastat
Controllers are primary safety limit-rated devices
designed for use with oil fired boilers with line voltage
burners and circulators. Many boilers do not include
wiring or control compartments as part of the design, but
are provided with an integral, replaceable, immersion well
that is the mounting hardware for the Aquastat
Controllers. Wiring to the other controls is done through
flexible metal conduit.
Fig. 5. Circuit board, showing sensor connection and
well holes for vertical mount models.
Fuse
The 1 Amp fuse located near the transformer is intended
to protect the EnviraCOM circuit from incorrect wiring. The
Aquastat will continue to function should the fuse blow or
be removed though no EnviraCOM communication will be
possible on the bus and Err 6 will be displayed. See
Table 10.
For boilers that do include a remotely (flush) mounted
control, the wiring may be completed with conduit or
routed behind the boiler sheet metal.
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L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS
A separate electromechanical high-limit is not required in
a system that uses this control to meet Underwriters
Laboratories Inc. requirements for oil-fired boiler
assemblies, UL 726.
Table 3. Adjustable Features.
Definition
Display
HL_
Hdf
High Limit.
On the L7224 models, the High Limit, Low Limit, Low Limit
Differential, and Anti Short-Cycle time can be adjusted to
the setting recommended by the boiler OEM. On the
L7248 models, the High Limit, and Anti Short-Cycle time
are also adjustable, see “Adjusting Settings”.
High Limit Differential.
LL_
Low Limit. (L7224A, C)
Ldf
Low Limit Differential (L7224A, C)
External Low Limit (L7248L only)
ELL
duu
The overall range of the High Limit is from 130 °F to
240 °F (54 °C to 116 °C). Select devices may have
different ranges. Some models have limited ranges on the
High Limit setpoint; this limited range is listed on the
device label.
ZR input configured as external Domestic Hot
Water (DHW) request (ON/OFF) (L7224A,C/
L7248L)
ASC
otL*
otH*
btL*
bP*
Anti Short-Cycle Timeout (seconds); “OFF” is
disabled.
Some models also have a Low Limit and Low Limit
Differential adjustment. The range of the Low Limit is from
110 °F to 220 °F (43 °C to 104 °C). Select devices may
have different ranges.
Outdoor Temperature Low (minimum)
parameter for the outdoor reset curve (°F or °C)
Outdoor Temperature High (maximum)
parameter for outdoor reset curve (°F or °C)
The Zr setting can be set to DHW, Zoning, or for tankless
coil applications depending on the L7224/L7248.
Boiler Temperature Low (minimum) parameter
for outdoor reset curve
If an Outdoor Reset Module is installed, the reset curve
can be set by entering the minimum outdoor temperature,
minimum (boiler) temperature, and maximum outdoor
temperature on the 3-digit display. The range of the
minimum outdoor temperature is from -40 °F to 40 °F (-
40 °C to 4.4 °C) and has a default setting of 0 °F (-18 °C).
The range of the maximum outdoor temperature is from
30 °F to 70 °F
(-1.1 °C to 21.1 °C) and has a default setting of 40 °F. The
range of the minimum (water or boiler) temperature is
from 80 °F to 180 °F (26.7 °C to 82.2 °C) and has a
default setting of 130 °F. See the “Outdoor Reset Module”
Installation Instructions (form number 69-2335) for more
information on setting the boiler reset curve and all related
parameters.
Boost Period (minutes). “OFF” is displayed if
Boost is inactive
bS*
Boost step (°F or °C) shown only if Boost is
active (bP=ON)
UUS*
tPL**
tPt**
Warm Weather Shutdown Temperature
(°F or °C)
Thermal Purging Limit Temperature (°F or °C),
“OFF” if disabled
Termal Purging Time Delay (minutes), shown
only if tPL is enabled
PC
Pump Cycling (ON / OFF)
Temperature units (°F or °C)
F-C
* Settings available for adjustment on the 3-digit display
only if a W8735Y1000 or W8735S1000 Outdoor Reset
Kit is installed.
**Settings available for adjustment only when the
W8735Y1000 or W8735S1000 Outdoor Reset Kit is
NOT installed.
The L7224A,C and L7248A,C,L are designed for use with
24 Vac electronic and electromechanical thermostats or
EnviraCOM™ enabled thermostats, and have screw-type
terminals for easy field connection.
Adjusting Settings
Then press the UP and/or DOWN buttons to move the set
point to the desired value, to change between °F and °C,
or to enable (On) or disable (Off) the External Low Limit.
After 60 seconds without any button inputs, the control will
automatically return to the RUN mode.
To discourage unauthorized changing of Aquastat
settings, a procedure to enter the ADJUSTMENT mode is
required. To enter the ADJUSTMENT mode, press the
UP, DOWN, and I buttons (Refer to Fig. 5) simultaneously
for three seconds. Press the I button until the feature
requiring adjustment is displayed:
Display
In the RUN mode, the Aquastat will flash “bt” (boiler temp)
followed by the temperature (i.e., 220), followed by °F or
°C.
To read boiler settings, press the I key to read the
parameter of interest. For example, press I and High Limit
(HL) is displayed, followed by a three-digit number, i.e.,
220, followed by °F or °C. Pressing the I button again (on
L7224 models) will display the Low Limit (LL) followed by
a three-digit number and the corresponding degree
designator. See Display Readout, Table 4.
After approximately 60 seconds without any key presses,
the display will enter a dim display mode. To return to the
bright display mode, simply press any key.
5
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L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS
has not gone below the Low Limit setting (minus the
Differential); or, ZR input is not powered with 120
Vac (only L7248L with ELL set On).
Table 4. Display readout definitions.
2. High Limit: Boiler temperature went above the High
Limit setting and has not dropped below the High
Limit setting (minus the Differential).
3. Low Limit: Boiler temperature went below the Low
Limit setting (minus the Low Limit Differential) and
has not gone above the Low Limit setting; or, ZR
input is powered with 120 Vac (only L7248L with
ELL set On).
4. Error: The controller has detected an error condition
(e.g., open sensor) and has shut down the burner
output. The ZC output is energized. The controller
continues to monitor the system and automatically
restarts if the error condition clears. Refer toTable 4.
Text
Err
Description
Display
Error Code (if one is present)
bT
Boiler Temperature
1
HL
HdF
LL
High Limit
High Limit Differential
Low Limit (L7224 only)
Ldf
tt
Low Limit Differential (L7224 only)
Local Thermostat Status
The operating sequence for the L7224/L7248 is shown in
Table 6–9.
ttE
brn
Cir
ZC
Zr
EnviraCOM Thermostat Status
B1 (Burner) output (ON or OFF)
C1 (Circulator) output (ON or OFF)
ZC (Zone Control) output (ON or OFF)
High Limit Controller
The High Limit opens and turns off the burner when the
water temperature reaches the setpoint. The High Limit
automatically resets after the water temperature drops
past the setpoint and through the Differential. The L7248
models have High Limit Differential presets of 15 °F
(8 °C). The L7224 models have High Limit Differential
presets of 10 °F (6 °C).
ZR (Zone Request) Call for HEAT (ON or OFF)
External Low Limit Enabled (L7248L only)
ELL
duu
ZR Configured as Domestic Hot Water
Request (L7224, L7248L only)
Low Limit and Circulator
Controller
On a temperature rise, with the adjustable Differential at
the default setting of 10 °F (6 °C), the burner circuit
breaks and the circulator circuit makes (assuming no call
for heat is present) at the Low Limit setpoint. On a
temperature drop of 10 °F (6 °C) below the Low Limit
setpoint, the burner circuit makes and the circulator circuit
breaks. See Fig. 7.
ASC
bSP
dhc
ot
Anti Short-Cycle Timeout
2
Boiler Set-Point
3
DHW Module Connected (YES or NO)
2
Outdoor Temperature
2
otL
otH
btL
bP
Outdoor Temperature Low
2
Outdoor Temperature High
2
SWITCH BREAKS ON
TEMPERATURE RISE.
BURNER TURNS OFF.
Boiler Temperature Low
2
HIGH LIMIT
SETTING
CIRCULATOR OPERATES
ON A CALL FOR HEAT.
Boost Period
L7224: 10°F (6°C)
DIFFERENCE
2
SWITCH MAKES ON
TEMPERATURE FALL.
BURNER OPERATES ON A
CALL FOR HEAT.
bS
Boost Step
L7248: 15°F (8°C)
DIFFERENCE
2
UUS
1
Warm Weather Shutdown Temperature
LOW LIMIT
SETTING
WITH NO HEATING
Display shows local setting; not the setting as modified by an
external enviracom control.
Settings are viewable only if the outdoor reset module and out-
door temperature sensor are installed and functioning properly.
Settings are viewable only if the domestic hot water module
and sensor are installed and functioning properly.
DEMAND, SWITCH BREAKS
10ºF (6ºC)
DIFFERENCE
ON TEMPERATURE RISE.
1
2
SWITCH MAKES ON
TEMPERATURE FALL,
BURNER IS ON TO
MAINTAIN MINIMUM
WATER TEMPERATURE.
CIRCULATOR IS OFF.
3
WHEN WATER REACHES LOW LIMIT SETTING, THE BURNER SHUTS
OFF OR THE CIRCULATOR PUMP STARTS (WHEN CALLING FOR HEAT).
1
Operation
M23364
The L7224 and L7248 models can be in any of four
operational states: Normal, High Limit, Low Limit and
Error. The controller moves back and forth from
High Limit to Normal to Low Limit state as part of normal
operation. Only devices having High Limit settings are
restricted to the High Limit and Normal states. However,
the controller will enter the Error state when there is an
abnormal condition. The operating states are:
Fig. 7. Setpoints and differentials.
Anti Short-Cycle Feature
The Anti Short-Cycle feature allows for field selection of a
delay time between burner cycles. Should a call for heat
occur following the end of the previous heat cycle and
before the Anti Short-Cycle delay time is expired, the
circulator will be allowed to run, but the burner will be held
off until the time has elapsed. The range of the Anti Short-
Cycle time is from OFF to five minutes.
1. Normal: Boiler temperature went below the High
Limit setting (minus the Differential) and has not
exceeded the High Limit setting; or, the boiler
temperature went above the Low Limit setting and
68-0281—16
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L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS
NOTE: This feature is blocked if a Domestic Hot
When the Boiler temperature reaches the Frost Protection
Limit temperature plus a fixed 10 °F differential, the burner
is turned off unless requested to stay on due to a different
demand.
Water demand occurs. Domestic Hot Water
demands are serviced immediately, without
any delay.
NOTE: When the Aquastat is connected to the oil
primary and/or thermostat via the EnviraCOM
bus, the Anti Short-Cycle time does not apply
to recycle events such as loss of airflow or
flame. It applies only to loss of demand.
Thermal Purge Operation
The intent of thermal purge is to insure usable residual
heat in the boiler is circulated until it is sufficiently
depleted from the system before the burner is allowed to
fire. To that end, on a call for heat, the burner is held off
while the circulator runs until the boiler temperature drops
to the thermal purge temperature or a time delay is
exceeded. Both of these parameters are adjustable.
When the boiler temperature reaches the thermal purge
temperature, the burner is allowed to fire. Thermal purge
is only applied to cold start Aquastat models (L7248) and
will not interfere with domestic hot water call for heat or
boilers equipped with Honeywell outdoor reset
ZR-Domestic Hot Water (DHW)
Request
The ZR terminal can be selected to service an indirect
water heater heat request. This parameter is set via the 3
digit display (see Adjusting Settings section of this
document). A heat request via the ZR terminal will have
priority over all other features such as the Anti Short-
Cycle feature or those enabled by the Outdoor Reset
Module (See form #69-2335 for more information).
must be set, thermal purge is not applied.
In addition to the thermal purge temperature and thermal
purge time delay parameters, two other conditions release
the Aquastat from thermal purge in order to maintain
comfort in the space:
Frost Protection
The Frost Protection function protects the boiler and
potentially the boiler plumbing from possible damage
which may occur should the water in the system begin to
freeze. The Frost Protection feature is enabled only in the
L7248 (cold start models). The feature default setting is
enabled (ON), but can be disabled using the 3-digit
display. See “Adjusting Settings” on page 5.
•
The boiler temperature has dropped 10 °F from the
beginning of the thermal purge.
•
Boiler temperature is cooling at a rate greater than
5 °F/minute while the circulator is running.
The thermal purge feature applies to single zone as well
as multi-zone applications.
When the Boiler temperature drops to the Frost Protection
Limit temperature (fixed 40 °F), the burner is forced on.
The Circulator and ZC outputs remain in the same state
as before the Frost Protection function was enabled.
They can be either ON or OFF during the Frost Protection
cycle.
Thermal Purge Settings
Some thermal purge parameters are configurable using
the 3 digit display. See “Adjusting Settings” on page 5.
Thermal purge may be disabled by setting the thermal
purge temperature limit to "OFF".
Table 5. Thermal Purge Settings.
Parameter name
Boiler temperature drop
Minimum value
Not adjustable
120 °F (or OFF)
1 minute
Maximum Value
Not adjustable
160 °F
Default
10 °F
Thermal purge temperature limit
Thermal purge temperature rate of drop
Thermal purge time delay
140 °F (L7248)
5 °F/minute
2 minutes
Not adjustable
10 minutes
Thermal Purge and Domestic Hot
Water
The thermal purge feature is automatically disabled
whenever there is a call for domestic hot water either from
the Zr terminal or from the DHW Module to insure hot
water is available in a timely manner. See “ZR-Domestic
Hot Water (DHW) Request” on page 7.
CHECKOUT
Put the system into operation and observe at least one
complete cycle to make sure that the controller operates
properly. See TROUBLESHOOTING section to use LED
to assist in determining system operation.
TROUBLESHOOTING
When attempting to diagnose system performance,
reference to the LED display can help to identify specific
areas not working properly. The LED display will scroll
Err, followed by a digit (1-8). Refer to Table 10 and 11 for
a description of each error and suggested actions.
Pump Cycling
The Pump Cycling feature exercises the system pump for
15 seconds after a non-adjustable five day period of no
boiler activity. The Pump Cycling feature default setting is
enabled (ON) but can be disabled (OFF) using the 3-digit
display. See “Adjusting Settings” on page 5.
7
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L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS
LINE VOLTAGE INDIRECT
TANK AQUASTAT
L1
(HOT)
W8735Y1000 OR
W8735S1000
INDIRECT
TANK
CIRCULATOR
L1
(HOT)
L2
1
2
3 OT OT
1
L2
C7089U
OUTDOOR
SENSOR
2
T
T
3
2
1
SENSOR
ZR
L1
LINE
L2
VOLTAGE
CIRCULATOR
C2
B2
C1
B1
ZC
LINE
VOLTAGE
OIL BURNER
RELAY
1
2
OUTDOOR RESET MODULE IS OPTIONAL. W8735S1000 WIRED OUTDOOR
RESET MODULE SHOWN.
FOR BEST PERFORMANCE SET DUU=”ON”.
M32023A
Fig. 8. L7224A,C; L7248L single heat zone with indirect water tank and circulators. Optional Outdoor Reset
Module.
68-0281—16
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L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS
Table 6. L7224/L7248 Controller Operating Sequence.
Action
System Response
Thermostat calls for heat.
Circulator starts when water temperature is above Low Limit setting (if
applicable) or above the Thermal Purge Temperature Limit (tPL) if
Thermal Purge is enabled. Boiler temperature is checked. Burner
starts when water temperature is below High Limit setting minus the
differential or at or below the Thermal Purge Temperature Limit (tPL)
for cold start boilers if the Thermal Purge Temperature Limit is
enabled. If tPL is enabled, the burner may also start if the boiler
temperature is cooling at 10 ºF or greater per minute or the Thermal
Purge Time Delay (tPt) has expired.
If Anti Short-Cycle Time is enabled, the burner does not start until the
set Anti Short-Cycle Time between cycles expires after the previous
call for heat was satisfied.
Boiler temperature exceeds the High Limit.
Thermostat is satisfied.
Burner is turned off. Burner restarts when the water temperature
drops below the High Limit setting minus the Differential. If Thermal
Purge is enabled, the burner is turned on when either the Thermal
Purge Temperature Limit is reached, the Thermal Purge Time Delay
has expired or the boiler temperature cooling rate exceeds 10 ºF/
minute.
Circulator and burner turn off.
Boiler temperature drops below the Low Limit Burner is turned on, Circulator is turned off. Burner stops when the
setting minus the differential (if applicable).
water temperature exceeds the Low Limit setting. Power to Zc is
removed.
Error condition
1-5.
If an error condition is detected, all outputs except ZC are shut down.
Burner is off. Control continues to function and restarts when error is
corrected.
During the error check sequence, the system checks for drift in the
sensor and corrosion in the connections.
Error condition 6.
Error condition 7.
EnviraCOM communication is not available.
The control has reset the High Limit, Low Limit and Differential setting to
a default setting and will continue to run at those settings.
Performance of the system will be degraded.
Error condition 8.
If the error condition is detected, all outputs except ZC are shut down.
Burner is off. Control continues to function and restarts when all three
user keys have been pressed longer than 60 seconds.
Error condition 9*.
Error condition 10*.
System continues to run with no outdoor reset functionality
System continues to run with outdoor reset parameters enabled as
programmed. Error cleared automatically.
Error condition 11*.
System continues to run with boiler temp set to High Limit.
* Error condition only available when the Outdoor Reset Module is installed.
Table 7. L7224/L7248 Controller Operating Sequence with multiple zones connected through the ZR terminal.
Action
System Response
Zone Request (ZR) terminal is connected to Boiler temperature is checked. Burner starts when water temperature
L1 (Zone calls for heat).
is below High Limit setting or at or below the Thermal Purge
Temperature Limit (tPL) for cold start boilers if the Thermal Purge
Temperature Limit is enabled. If tPL is enabled, the burner may also
start if the boiler temperature is cooling at 10 ºF or greater per minute
or the Thermal Purge Time Delay (tPt) has expired. Anti Short-Cycle
Time is applied, see Table 6.
Boiler temperature exceeds the High Limit.
Burner is turned off. Burner restarts when the water temperature
drops below the High Limit setting minus the Differential. If Thermal
Purge is enabled, the burner is turned on when either the Thermal
Purge Temperature Limit is reached, the Thermal Purge Time Delay
has expired or the boiler temperature cooling rate exceeds 10 ºF/
minute.
Zone Request input is de-energized (Zones
are satisfied).
Burner turns off.
Boiler temperature drops below the Low Limit Burner turns on and Zone Control is de-energized. Burner turns off
setting minus the differential (if applicable).
and Zone Control is re-energized when the water temperature
exceeds the Low Limit setting.
9
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L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS
.
Table 8. Controller Operating Sequence with External Low Limit device connected trough the ZR terminal.
Action
System Response
Zone Request (ZR) terminal is connected to Boiler temperature is checked. Burner starts when water temperature
L1 (External Low Limit call for heat).
is below High Limit setting. Circulator turns off.
Boiler temperature exceeds the High Limit.
Burner is turned off. Burner restarts when the water temperature
drops below the High Limit setting minus the Differential.
Zone Request input is de-energized (External Burner is turned off.
Low Limit is satisfied).
Table 9. L7224 Controller Operating Sequence with Domestic Hot Water connected trough the ZR terminal.
Action
System Response
Zone Request (ZR) terminal is connected to Boiler temperature is checked. Burner starts when water temperature
L1 (Domestic Hot Water calls for heat).
Boiler temperature exceeds the High Limit.
is below High Limit setting.
Burner is turned off. Burner restarts when the water temperature
drops below the High Limit setting minus the Differential.
Zone Request input is de-energized
(Domestic Hot Water is satisfied).
Burner is turned off.
Table 10. LED Error Codes.
Aquastat
EnviraCOM
Alarm
Error Code
Cause/Action
Aquastat sensor fault; check water sensor.
ECOM fault; check EnviraCOM™ wiring.
Err1
Err2
Err3
Err4
Err5
18
18
Excessive electrical noise or frequency out of range. Hardware fault; replace controller.
B1 fault; check B1 wiring/voltage.
18, 58
64
Low Line; check L1-L2, 110 Vac.
59
a
Warning: Fuse; check ECOM wires, replace fuse.
92
Err6
Err7
Warning: EEPROM, HL, LL, Hdf, Ldf; reset to default values.
N/A
b
Repeated B1 fault (voltage present at B1 when output is turned off); check B1 wiring/voltage. 25
Err 8
a
Warning: Outdoor Reset System failure; communication to Outdoor Reset Module lost,
Outdoor Reset Module failure, multiple outdoor temperature sensors detected on the bus, or
outdoor temperature sensor failure. Check EnviraCOM wiring (1, 2, 3), check sensor wiring.
50, 53, 149
Err9
a
a
Warning: Boost Failure; Boost Mode active at least once per cycle for the last 60 consecutive 150
cycles. Check Outdoor Reset curve settings.
Err 10
DHW Module/Sensor failure; communication to DHW Module lost, DHW Module failure, or 146, 147,
Err 11
a
temperature sensor failure. Check EnviraCOM wiring (1, 2, 3), check sensor wiring.
148
Warnings are generated to enunciate the system is not operating optimally, but the Aquastat is still operating and
maintaining boiler temperature. In the instance where an Outdoor Reset Module is used, the warnings may indicate a
reset curve setting error one or more features is not running optimally, and the Aquastat is reverting to default settings
or has stopped running the Outdoor Reset algorithms. The warnings are cleared when the issue(s) is resolved.
To clear Err 8 condition, depress and hold all three user keys simultaneously for 60 seconds. Err 8 condition clears
and display returns to normal. Err 8 condition is designed to catch welded relays on the Aquastat and will normally
only occur near end of life for the control. If Err 8 condition has occurred early in the controls life, be sure to check for
voltage feedback to B1 when B1 should be off and check current draw on b terminal to be sure oil burner is not draw-
ing excessive current. Err 8 condition will keep repeating if B1 fault is not cleared.
b
Table 11. Troubleshooting Guide
System
Diagnostic
Condition
Condition
Check
Action
Turn system power on.
Boiler is cold, Display is OFF. 120 Vac System power.
house is cold.
Display is ON.
24 Vac T-T
No 24 V; replace control.
24 V present; disconnect
thermostat, short T-T.
Boiler starts, check wiring and thermostat.
120 Vac at B1-B2
Refer to Err on display.
10
•
•
If no, replace control.
If yes, check burner and wiring.
—
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L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS
Table 11. Troubleshooting Guide
Diagnostic
System
Condition
Condition
Check
Action
Boiler is hot,
house is cold.
Display is ON.
120 Vac at C1-C2
•
•
•
•
120 Vac at C1-C2, check wiring to pump.
Wiring OK, is pump running?
If not, replace the pump.
If pump is running, check for trapped air or
closed zone valves.
Boiler below the Low Limit
—
temperature, wait for boiler to go
above Low Limit temperature.
Boiler above LL? If yes, check for
120 Vac between ZC and L2.
•
•
If no 120 Vac, replace control.
If yes, check zone relays, circulators and
wiring.
ELL setting (L7248L only)
•
•
Set ELL to Off for multizone system (see Fig.
11).
Set ELL to On for External Low Limit (see
Fig. 13).
Boiler above LL? If yes, check 120
Vac at ZR-L2 (only L7248L with
ELL set On)
•
•
If no 120 Vac, check C1-C2 (see above).
If yes, check the External Low Limit control.
Boiler is hot,
no hot potable
water.
Display is ON.
Boiler Demand signal from the
water heater (either 120 Vac at
ZR-L2, or 0 Vac on T-T; depends
on installation and “duu” setting)
•
•
24 Vac on T-T (or 0 Vac on ZR-L2), check
wiring to water heater
Wiring OK, check the water heater
“duu” setting
•
•
Set duu to ON if 120 Vac water heater
demand is connected to ZR
Set duu to OFF if open/closed water heater
demand is connected to T-T
Check DHW Module and DHW
Sensor
•
DHW Module not properly connected and/or
DHW Sensor improperly positioned
TO ADDITIONAL R845A
RELAYS FOR OTHER ZONES
ZONE 2
CIRCULATOR
LOW
VOLTAGE
THERMOSTAT
1
2
L1
L7224
L2 (HOT)
R845A RELAY ZONE 2
T
T
6
5
3
2
1
3
SENSOR
4
1
ZR
L1
LINE
2
VOLTAGE
L2
CIRCULATOR
C2
B2
C1
B1
ZC
ZONE 2
LOW VOLTAGE
THERMOSTAT
LINE
VOLTAGE
OIL BURNER
RELAY
1
2
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
CONTROL CASE MUST BE CONNECTED
TO EARTH GROUND. USE GROUNDING
SCREW PROVIDED.
M27115
Fig. 9. L7224A,C multizone system with circulator connections.
11
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L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS
LINE VOLTAGE
W8735Y1000 OR
W8735S1000
INDIRECT
TANK AQUASTAT
3
2
1
1
2
3 OT OT
C7089U1006
OUTDOOR
SENSOR
6
TH9421C
INDIRECT
TANK
CIRCULATOR
R7184/R7284
L1
(HOT) L2
L2
T
2
1
3
1
T
T
LIMIT
L1
L7224
3
L2
2
1
T
3
2
1
5
3
BURNER
MOTOR
ENVIRACOM™
TERMINAL
BURNER
MOTOR
SENSOR
7
3
3
IGNITER
VALVE
IGNITER
VALVE
ZR
L1
LINE
VOLTAGE
CIRCULATOR
L2
C2
B2
C1
B1
ZC
4
TO REMOTE
ALARM
CIRCUIT
CAD
CELL
CAD
CELL
2
JUNCTION
BOX
LEGEND
SCREW TERMINAL
1/4 IN. (6 MM) QUICK CONNECT TERMINAL
SOLDERLESS WIRE CONNECTION
5
6
ENVIRACOM™ TERMINAL 3 IS ALSO THE FIRST THERMOSTAT TERMINAL.
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
OPTIONAL OUTDOOR RESET MODULE AND OUTDOOR SENSOR.
W8735S1000 WIRED OUTDOOR RESET MODULE SHOWN.
OPTIONAL FEATURE ON SELECT MODELS.
REFER TO DEVICE LABEL FOR WIRE COLOR CODE.
VALVE IS OPTIONAL ON SPECIFIED MODELS.
2
3
4
7
DUU MUST BE SET TO “ON” ON THE AQUASTAT.
M32025B
Fig. 10. L7224A,C single zone system with circulator and indirect water tank with EnviraCOM™ thermostat.
68-0281—16
12
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L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS
ELL=OFF
TO ADDITIONAL R845A
RELAYS FOR OTHER ZONES
CIRCULATOR
ZONE 2
1
L1
(HOT) L2
R845A RELAY ZONE 2
6
5
3
4
1
2
ZONE 2
LOW VOLTAGE
ENVIRACOM
TERMINALS
THERMOSTAT
4
LOW VOLTAGE
THERMOSTAT
W8735Y1000 OR
W8735S1000
2
L7248L
T
T
1
2
3 OT OT
3
2
1
3
C7089U1006
OUTDOOR
SENSOR
SENSOR
ZR
W8735S1008
5
DOMESTIC HOT
WATER MODULE
L1
L2
C2
B2
C1
B1
ZC
LINE
VOLTAGE
CIRCULATOR
1
2
3 TS TS
LINE
VOLTAGE
OIL BURNER
RELAY
32003971-003
TEMPERATURE
SENSOR
1
2
3
4
5
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
CONTROL CASE MUST BE CONNECTED TO EARTH GROUND. USE GROUNDING SCREW PROVIDED.
OPTIONAL OUTDOOR RESET MODULE AND OUTDOOR SENSOR. W8735S1000 WIRED OUTDOOR RESET MODULE SHOWN.
ENVIRACOM TERMINALS.
OPTIONAL DOMESTIC HOT WATER MODULE AND TEMPERATURE SENSOR.
M29655A
Fig. 11. L7248L multizone system with circulator connections.
13
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L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS
W8735Y1000 OR
W8735S1000
W8735S1008
MULTI-ZONE
RELAY PANEL
1
2
3 TS TS
1
2
3 OT OT
C7089U
OUTDOOR
SENSOR
7
6
32003971-003
TEMPERATURE
SENSOR
T
T
9
8
R7184/R7284
L1
1
(HOT) L2
T
T
LIMIT
L1
L7224
3
L2
2
1
T
T
3
2
1
5
3
BURNER
MOTOR
ENVIRACOM™
TERMINAL
BURNER
MOTOR
SENSOR
3
3
IGNITER
VALVE
IGNITER
VALVE
ZR
L1
L2
C2
B2
C1
B1
ZC
LINE
VOLTAGE
CIRCULATOR
4
TO REMOTE
CAD
CELL
CAD
CELL
ALARM
CIRCUIT
2
JUNCTION
BOX
LEGEND
SCREW TERMINAL
1/4 IN. (6 MM) QUICK CONNECT TERMINAL
SOLDERLESS WIRE CONNECTION
6
OPTIONAL OUTDOOR RESET MODULE AND OUTDOOR SENSOR.
W8735S1000 WIRED OUTDOOR RESET MODULE SHOWN.
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
7
8
OPTIONAL DOMESTIC HOT WATER MODULE.
OPTIONAL FEATURE ON SELECT MODELS.
2
3
4
5
WIRE ONLY THE ENVIRACOM TERMINALS (1, 2, 3) ON OIL PRIMARY
IF CONNECTING TO REMOTE DIAGNOSTICS, OTHERWISE CONNECT
A JUMPER BETWEEN THE TT TERMINALS.
REFER TO DEVICE LABEL FOR WIRE COLOR CODE.
VALVE IS OPTIONAL ON SPECIFIED MODELS.
9
ZONE PANEL TERMINALS MAY HAVE DIFFERENT LABEL. CHECK
PANEL MANUFACTURER SPECIFICATIONS FOR WIRING INSTRUCTIONS.
M32024A
ENVIRACOM™ TERMINAL 3 IS ALSO THE FIRST THERMOSTAT TERMINAL.
Fig. 12. L7224/L7248 multizone system with Outdoor Reset and Domestic Hot Water Modules (indirect tank
applications).
68-0281—16
14
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L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS
ELL=ON
1
L2 L1 (HOT)
L6006
R
LOW LIMIT
CONTROLLER
W
B
LOW
VOLTAGE
THERMOSTAT
2
L7248L
T
T
3
2
1
SENSOR
ZR
L1
L2
LINE
VOLTAGE
CIRCULATOR
C2
B2
C1
B1
ZC
LINE
VOLTAGE
OIL BURNER
RELAY
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
CONTROL CASE MUST BE CONNECTED TO EARTH GROUND.
USE GROUNDING SCREW PROVIDED.
M27113
Fig. 13. L7248L External Low Limit connections.
15
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L7224A,C; L7248A,C,L OIL AND ELECTRIC BOILER ELECTRONIC AQUASTAT CONTROLLERS
Automation and Control Solutions
Honeywell International Inc.
1985 Douglas Drive North
® U.S. Registered Trademark
© 2013 Honeywell International Inc.
68-0281—16 M.S. Rev. 09-13
Golden Valley, MN 55422
Printed in United States
customer.honeywell.com
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