Thermo Products Furnace MDA1 100N User Manual

INDUCED DRAFT HIGHBOY AND

COUNTERFLOW/HORIZONTAL

GAS FURNACE

INSTALLATION AND SERVICE MANUAL

MODELS

MHA1-50N

MHA1-75N

MHA1-100N

MHA1-125N

MDA1-50N

MDA1-75N

MDA1-100N

MDA1-125N

: IF YOU DO NOT FOLLOW THE SAFETY PRECAUTIONS BELOW AND IN THIS MANUAL,

A FIRE OR EXPLOSION MAY RESULT CAUSING PROPERTY DAMAGE, PERSONAL INJURY, OR

LOSS OF LIFE.

DO NOT STORE OR USE GASOLINE OR OTHER FLAMMABLE VAPORS AND LIQUIDS IN THE

VICINITY OF THIS OR ANY OTHER APPLIANCE.

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.

LEAVE THE BUILDING IMMEDIATELY.

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. (REFERRED TO IN THESE INSTRUCTIONS AS A QUALIFIED

HEATING CONTRACTOR).

PLEASE READ THESE INSTRUCTIONS PRIOR TO INSTALLATION, INITIAL FIRING, AND BEFORE

PERFORMING ANY SERVICE OR MAINTENANCE. THESE INSTRUCTIONS MUST BE LEFT WITH

THE HOMEOWNER AND SHOULD BE RETAINED FOR FUTURE REFERENCE BY

QUALIFIED SERVICE PERSONNEL.

THERMO PRODUCTS, LLC.

BOX 217

MG-1008

ECN 4283-MA

NORTH JUDSON, IN 46366

PHONE: (574) 896-2133

MADE IN USA

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All installations and services must be performed by qualified service personnel.

VI. INSTALLER’S INSTRUCTIONS TO USER ......................................................41

APPENDIX A: SOURCES FOR REFERENCED STANDARDS .......................42

APPENDIX B: SEQUENCE OF OPERATION ..................................................43

APPENDIX C: TROUBLESHOOTING FLOWCHART ......................................45

APPENDIX D: PARTS PACKAGE COMPONENTS .........................................49

APPENDIX E: REPLACEMENT PARTS LIST..................................................50

APPENDIX F: ELECTRICAL DIAGRAMS ........................................................54

WARRANTY......................................................................................................59

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All installations and services must be performed by qualified service personnel.

Notice to the Installer

Installation of this gas-fired furnace must be performed by a qualified installer in

accordance with all local codes and authorities having jurisdiction. In the absence of

local governing codes, installation shall conform to these instructions and to the

regulations of the National Fuel Gas Code, ANSI Z223.1/NFPA 54-2002 and/or,

National Gas and Propane Installation Codes CSA B149.1, or the latest editions

thereof.

A qualified installer, also referred to in this instruction manual as a “qualified heating

contractor”, is an individual, or agency, that is responsible for the installation and

adjustment of the equipment. A qualified installer is properly licensed and

experienced to install gas-burning equipment in accordance with all local codes and

ordinances.

Any reference to L.P. or propane gas in this manual, any other label, or markings

on the furnace is to be construed to be propane HD-5, a commercial grade of

liquefied petroleum gases composed of a minimum of 90 percent liquid propane

(C₃H₈).

Material and Workmanship

This furnace was built with the highest quality materials and attention to

workmanship. However, omissions and defects occasionally occur. Before

installing the furnace, inspect the furnace thoroughly. If missing parts, defective

material, or poor workmanship are evident, report the model and serial

numbers imprinted on the furnace rating label to the seller.

Packaging

This is a complete, factory-assembled furnace contained within one package.

However, certain parts, including, air filter(s), air filter rack(s), the venting system

must be assembled to the furnace, in the field.

Shipping Damage

If this furnace was damaged during transit, please immediately request the

transportation company inspect the furnace and issue a concealed damage

report. The party receiving the furnace should file the claim for shipping

damage. Report any shipping damage immediately.

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All installations and services must be performed by qualified service personnel.

It is absolutely essential that a damage report be obtained. If a concealed

damage report is not obtained, we cannot provide assistance in recovering your

claim against the transportation company.

Warranties

The manufacturer of this equipment assumes no liability for any

damages resulting from unauthorized modifications made to the

furnace, or components thereof, or improper installation of the furnace

in the field. Furthermore, any such field modifications VOID THE

WARRANTY and place the responsibility for safe and reliable operation

of the furnace on those who performed the modification(s).

Make certain the warranty cards are returned. These must be on file to verify

installation dates for replacement of any warranted part(s).

I. Safety

The following guidelines and warnings should be read and understood

before continuing with the installation of this furnace. Failure to follow

these guidelines can result in improper and unsafe operation of this

appliance, which can cause substantial property damage, severe

personal injury, or death.

These instructions must be read in their entirety before installing the furnace. It is

the installer's responsibility to do the following:

1. Use only with the type of gas approved for this furnace. Refer to the furnace

marking plate.

2. Install this furnace only in a location and position as specified in Section II, B

of this manual.

3. Provide adequate combustion and ventilation air to the furnace space. Refer

to Sections II, E of this manual.

4. Connect this furnace to an approved vent system only. Combustion products

must be vented outdoors. Refer to Section II, J of this manual for vertical

vented units.

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All installations and services must be performed by qualified service personnel.

5. Never test for gas leaks with an open flame. Use a commercially available

soap solution made specifically for the detection of leaks to check all

connections. Refer to Section II, L of this manual.

6. Always adjust the furnace to operate within the furnace’s temperature-rise

range with a duct system, which has an external static pressure within the

allowable range. Refer to Section III, D of this manual.

7. Make sure supply and return air ducts are completely sealed to the furnace

casing. Ductwork must run to an area outside the air space where the

furnace is located and be sealed where it runs through walls, ceilings, and

floors. Refer to Section II, G of this manual.

8. This furnace is not to be used for temporary heating of buildings or structures

under construction

9. Refer to MDA1 horizontal application Section II, F of this manual for safety

switch relocation associated with horizontal installation of the MDA1.

10.Inform and demonstrate to the user, the correct operation and maintenance

of the appliance as explained in the Users Information Manual.

11.Inform the user of the hazards of flammable liquids and vapors and to

remove such liquids and vapors from the vicinity of the appliance.

12.Inform the user of warnings and cautions as well as user information in the

sidewall venting manufacturer’s manual when sidewall venting is applied.

II. Installation Guidelines

A. Codes

All local codes and/or regulations take precedence over the instructions in this

manual and should be followed accordingly. In the absence of local codes,

installation must conform to the instructions and the regulations of the National

Fire Protection Association National Electrical Code, ANSI/NFPA70-2002, and

the National Fuel Gas Code, NFPA 54/ANSI Z223.1-2002, or the latest editions

thereof.

The heating capacity of the furnace proposed for installation should be based on

a rate of heat loss calculation made according to the manuals provided by the Air

Conditioning Contractors of America (ACCA) or ASHRAE.

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All installations and services must be performed by qualified service personnel.

B. Installation Location

• These furnaces are designed for indoor installation only.

• These furnaces are NOT to be used as construction heaters.

• The return air duct of the furnace must be sealed air tight to

prevent starvation of the combustion air, especially if the furnace

is located in a closet or confined area.

For best performance locate the furnace so that it is centralized with respect to

the duct system.

Place the unit so that proper venting can be achieved, with a minimum number

of elbows, in accord with the instructions in this manual. The furnace should be

located as close to the chimney (vertical venting) or to the outside vent wall

(horizontal venting) as practical.

The furnace must be located on a level, dry surface in an area, which is free

from and protected from excessive drafts. The furnace must be installed so that

the electrical components are protected from water. If the area becomes wet or

damp at times, the furnace should be raised above the floor using a concrete

base, bricks, patio blocks, etc.

When installing this furnace, provisions must be made to insure the supply of

adequate combustion and ventilation air in accordance with the air for

combustion and ventilation section of the National Fuel Gas Code, NFPA

54/ANSI Z223.1-2002, or latest edition, or applicable provisions of the local

building code. See Section II, E, of this manual

A furnace installed in a residential garage must be installed so the burners and

ignition source are located 18 inches or higher above the floor. Also, the furnace

must be located or protected to avoid physical damage by vehicles.

If this furnace is to be installed horizontally, see Section II, F, of this manual.

C. Closet and Alcove Installation

All furnace models may be installed in a closet or alcove on combustible flooring

with specified (standard) clearances to combustible construction. The furnace

shall not be installed directly on carpeting, tile or other combustible material other

than wood flooring. The MDA1-50, 75, 100, and 125, horizontal / counterflow

furnace, models requires an optional combustible surface-mounting base

for counterflow installation directly on combustible materials. The

combustible floor base model numbers are as follows: 50DA-BASE for MDA1-50

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and MDA1-75; 100CA-BASE for MDA1-100; and 125CA-BASE for MDA1-125.

refer to Figure 1.

Figure 1: Counter flow Furnace Combustible Surface-Mounting Base

D. Standard Clearances

Definitions of combustible material and non-combustible as issued by the

National Fuel Gas Code are as follows:

Combustible Material:

Materials made of or surfaced with wood, compressed paper, plant fibers,

plastics or other material that will ignite and burn whether flameproof or not or

whether plastered or not plastered.

Non-combustible Material:

Material which will not ignite and burn; such materials consisting entirely of steel,

iron, brick, concrete, slate, glass, plaster or combination thereof.

Table 1: Minimum Clearances to Combustible Materials

Sides & Rear

of Furnace

(in.)

Front of

Furnace

(in.)

Top of

Plenum

(in.)

Sides of

Plenum

(in.)

Model No.

Flue or Vent

(in.)

All Models

Covered by

This Manual

*6 in. clearance may be reduced to 1 in. with UL Recognized type B1 vent.

The minimum clearances are listed for fire protection. Clearances for servicing

and proper operation, the front of the furnaces and to all points on the furnace

requiring access must be 24 in.

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E. Air for Combustion and Ventilation

Relief openings in the front or top of the furnace casing should not

be obstructed or blocked. These openings supply combustion and

ventilation air to the furnace.

Chloride, fluoride, iodide, and bromide bearing compounds when present, even

in low concentrations, in air supplied for combustion to the furnace, can result in

accelerated and severe corrosion of the heat exchanger and/or the venting

systems. This condition can occur with less efficient furnaces, but is accelerated

on furnaces with efficiencies of 80% or greater.

Many, household chemicals contain chloride-bearing compounds. There are

many compounds representative of this classification of chemicals. A few

common examples are listed below.

•

Cleaning solvents

Varnish and paint removers

Bleaches

Fabric softeners

Water softener salt

Tile adhesives

Avoid installing the furnace in areas where it is evident these chemicals are

being stored, or used, within close proximity to the furnace. In addition, avoid

storing or using any chemicals of an unknown nature in close proximity to the

furnace. If it is necessary to store or use these chemicals in the same space as

the furnace, all containers should be sealed when not in use. If possible, keep

these chemicals in a separate, well-ventilated, room that is closed off, from the

furnace, with a door.

The furnace shall be installed in a location within the building that permits a

satisfactory supply of air for combustion, ventilation, and proper operation of the

venting system. While all forms of building construction cannot be covered in

detail in this manual, this requirement may usually be met by application of one

of the following methods in ordinary building construction. Consult the National

Fuel Gas Code, NFPA 54/ANSI Z223.1 – 2002, or the latest edition, for special

cases and further details. However, local installation codes always take

precedence and must be followed, if applicable.

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1. Utility Room (example of a confined space)

In buildings of unusually tight construction, such as those wherein weather

stripping and storm sash windows are used, two (2) permanent openings

connecting to a well-ventilated crawl space, attic, or with the outdoors

shall be provided. Each opening shall have a minimum free area of one

(1) square inch per 1000 BTUH of total input rating of all appliances to be

installed in the utility room. One opening should be located near, or in, the

ceiling of the room and the other should be located near, or in, the floor.

2. Full Basement (example of an unconfined space)

Where a furnace is installed in a full basement, infiltration is normally

adequate to provide air for combustion and ventilation.

When an opening in the outside wall must be provided, it should be furnished

with properly screened metal sleeves.

If an exhaust fan, or additional fuel burning appliances, are present in the

furnace room, there should be increased concern about providing adequate

airflow to the furnace. Additional efforts may be required to assure an adequate

supply of combustion and ventilation air is available to the furnace under all

conditions.

F. MDA1 Horizontal Installation

The auxiliary limit switch must be relocated in accordance with the

following instructions when installing this furnace horizontally.

DO NOT hang the horizontal / counterflow furnace from a structure

or surface by any integral part or fastener of the furnace. The furnace

was not designed to support itself in this manner.

The MDA1-50, 75, 100, and 125 furnaces may be installed in a horizontal

position by placing the furnace on the left or right side (as viewed from the front

in the upright position).

If the unit is placed on its right side the auxiliary limit switch located on the right

side of the house air blower must be moved to the opposite (left) side of the

blower (refer to Figure 2).

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A plenum angles kit, (AOPS4942) is available for connecting the supply plenum

to the furnace. The kit consists of four angles that are to be screwed to into the

predrilled holes in the base of the furnace using # 8 screws.

The horizontal furnace installation should be on a service platform large enough

to allow for proper clearances on all sides and service access to the front of the

furnace (refer to Table 1). If the furnace is suspended, it must be supported at

both ends and in the middle with clearance allowed for removal of both access

doors. Line contact is only permissible between lines formed by the intersection

of the top and two sides of the furnaces casing and the building joists, studs, or

framing.

Equipment must be

installed in

accordance with

regulations of the

National Board of Fire

Underwriters and the

National Fuel Gas

Code. Authorities

having jurisdiction

should be consulted

before installations

are made.

Figure 2: MDA1 Installed Horizontal

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G. Duct Work and Air Conditioning

Design and installation of the duct system should follow the current guidelines of

the Air Conditioning Contractors of America (ACCA) or the American Society of

Heating, Refrigeration and Air Conditioning Engineers, Inc. (ASHRAE).

All furnaces are tested over a range of external static pressure that simulates the

airflow resistance of the ductwork, fittings, and diffusers connected to the furnace

for a typical (average) duct system. The furnace blower and blower motor have

been selected to work successfully against the following range of duct system

resistance.

Recommended range of duct system resistance for all models: 0.2 to 0.5 in.

W.G. external static pressure.

When the furnace is installed in a small room, and no return air ducts are used,

the return openings to the unit should extend full size to a location outside the

furnace room.

If the furnace is used in connection with summer air conditioning (cooling), the air

conditioner’s evaporator coil must be installed on the air outlet side of the

furnace to avoid water vapor condensation in the furnace heat exchanger.

NOTICE: Return air grilles and supply registers in the air distribution system

should not be obstructed.

H. Filters/ Filter Installation

Filters must be installed external to the furnace casing.

It is necessary to cut the return air opening in one or both side(s) of the MHA1

models depending upon the needs of the specific installation.

This MHA furnace has been factory supplied with a high quality re-usable filter

rated for air velocities up to 600 ft/min. An optional Thermo Products filter rack

assembly (part no. AOPS7547 for MHA50, 75, 100 and AOPS7375 for the

MHA125) is available which, is sized for the filter provided.

If an optional Thermo Pride filter rack (Figure 3) is used with the furnace, square knock

outs have been provided on each side casing to act as a template for the cut out.

Scribe lines connecting the outside corners of each knockout, cut side casing along

lines. Position the open end of the filter rack so that it is accessible for filter

replacement. Attach the filter rack to the furnace with screws or pop-rivets along the

securing flange. Connect the return plenum to the filter rack and slide the filter into

place.

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FLANGE DIMENSIONS

(DUCT SIDE)

MHA1-50,75,100 15"

MHA1-125 19"

24-1/2"

24"

SECURING

FLANGE

(FURNACE SIDE)

OPEN END INTO WHICH

FILTER SLIDES

Figure 3: Optional Thermo Pride Filter Rack

I. Use of Non-Thermo Pride Filter Retention Means

Failure to comply with minimum filter installation requirements may

affect the performance and/or void the warranty on this furnace.

If a method other than a Thermo Pride filter rack is selected for retention of the

filter and/or use of a different filter type is desired, see Table 2 for minimum size

guidelines for selecting a filter system for the MHA1/MDA1 furnaces.

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Table 2: Minimum Filter Area Required (Sq. in.)

Maximum

Rate of

Velocity

(FPM)

Furnace Model

Filter Type

MHA1-50

MDA1-50

MHA1-75

MDA1-75

MHA1-100

MDA1-100

MHA1-125

MDA1-125

*THERMO

PRODUCTS

SUPPLIED

PERMANENT

FILTER

600

172

254

328

402

STANDARD

PERMANENT

FILTER

DISPOSABLE

TYPE

500

300

208

344

304

506

394

656

484

804

FILTER

* The Thermo Products supplied filter can be cut to size to fit other filter retention

systems as long as the minimum size requirement is met.

NOTICE: The filter areas in Table 2 are the minimum areas required based on

the flowrate generated by the furnace for standard heating speeds only. The

following formula can be used to determine the minimum filter area required for

cooling, if the unit is equipped with cooling. This value should then be compared

to the value shown in table 2 and the larger of the two should then be used for

determining the minimum filter area required for that installation.

FORMULA:

(tons of cooling)(400 CFM per ton)(144 sq. in. per foot) = filter area sq. inches

(max. air velocity of filter from table 5 for the filter type)

EXAMPLE: If you had an MHA1/MDA1-100 furnace and 4 tons of cooling and a

standard reusable filter.

4 tons x 400 CFM x 144 = 460 square inches for cooling

500

For heating an MHA/MDA-100 needs 328 square inches of standard reusable

filter. The filter system must be designed for the larger flow requirement

determined for cooling of 460 square inches. A filter would have to be sized so

that the area (length x width) was at least 460 sq. in.

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J. Venting

1. Vertical Venting

• The vent installation of this Category I furnace must be in

accordance with National Fuel Gas Code, NFPA 54/ANSI Z223.1-2002

or latest edition, and/or local building codes and these instructions.

• A furnace or any other gas utilization equipment must not be

connected to a chimney flue serving a separate appliance designed

to burn solid fuel.

• When venting two or more appliances into a common vent, the

smallest appliance must be vented into the top opening.

• The maximum gross stack temperature must not exceed 480°F

(249°C) under any circumstances

NOTICE: This section does not apply to units, which are sidewall vented. For

sidewall venting, see Section II, K, of this manual.

The following requirements must be followed when connecting this furnace to a

vent system.

The MHA1/MDA1 (induced draft gas highboy and counterflow/horizontal) series

furnace must be vented in accordance with these instructions into a factory built

chimney or vent complying with a recognized standard. Type B1 or double wall

vent as well as masonry chimneys lined with a lining material acceptable to the

authority having jurisdiction are acceptable as described in the venting tables

included in the appendix of the National Fuel Gas Code, NFPA 54/ANSI Z223.1-

2002, or latest edition.

A good vent is one that is sealed and has the capability of producing a -0.04 in.

W.G. draft with the capacity of handling the amount of flue gas that is introduced

to it.

The vent must be vertical or nearly vertical in design, unless equipped with a UL

listed mechanical venter.

This furnace must not be connected into any portion of a mechanical draft

system operating under a positive pressure.

This furnace shall not be vented into an unlined masonry or concrete chimney.

PVC piping is not an acceptable substitute for a chimney or a flue connector. A

chimney with an internal construction of stainless steel or some other material

that will withstand a gross flue gas temperature of 480ºF is required.

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These venting tables also include venting combinations, which apply to common

venting arrangements of two or more appliances. These requirements as well as

all the installation requirements outlined in this manual for an MHA1/MDA1

series furnace must be followed when an MHA1/MDA1 furnace is common

vented with another Category I gas appliance.

See also Section II, J, 2, of this manual, “Replacing an Existing Furnace From a

Common Vent” for information on testing the proper operation of appliances in a

common vent.

The minimum allowable chimney height is determined by the height of the

surrounding trees, roof, buildings and terrain. The chimney should extend 24"

above any surrounding obstructions. In cases where the chimney flue extends to

the basement floor, the draft can usually be improved by filling the base of the

chimney with sand to within 12" of the flue pipe after relocating the cleanout

cover.

All joints of the vent must be tightly sealed. The inside of the vent should be free

of all obstructions.

2. Replacing An Existing Furnace From a Common Vent

CARBON MONOXIDE POISONING HAZARD

Failure to follow the steps outlined below for each appliance connected to

the venting system being placed into operation could result in carbon

monoxide poisoning or death.

When an existing furnace is replaced or removed from a common vent serving

other appliances, the vent system may now be too large to properly vent the

remaining appliances only and must be modified accordingly. Failure to correct

an oversized vent can cause the formation of condensate, leakage or spillage of

combustion byproducts, which may cause property damage, personal injury, or

loss of life.

The steps below must be followed with each appliance, which is still connected,

to the common venting system. Each appliance should be placed in operation,

while the other appliances remaining connected to the common venting system

are not in operation.

1. Seal any unused opening(s) in the common venting system.

2. Visually inspect the venting system for proper size and horizontal pitch,

as required in the National Fuel Gas Code, NFPA 54/ANSI Z223.1 –

2002, or the latest edition. Determine there is no blockage or

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restriction, leakage, corrosion or other deficiencies which could cause

an unsafe condition.

3. Insofar as is practical, close all building doors and windows and all

doors between the space in which the appliances remaining connected

to the common venting system are located and other spaces of the

building.

4. Turn on clothes dryers and any appliance not connected to the

common venting system. Turn on any exhaust fans, such as range

hoods and bathroom exhausts, so they will operate at maximum

speed. Do not operate a summer exhaust fan.

5. Close fireplace dampers.

6. Follow the lighting instructions. Place the appliance being inspected in

operation. Adjust thermostat so appliance will operate continuously.

7. Test draft hood equipped appliances for spillage of flue gases at the

draft hood relief opening after 5 minutes of main burner operation. Use

the flame of a match or use a draft gauge.

8. If the improper venting is observed on any of the appliances during the

above testing, the common vent system must be corrected. Follow the

steps outlined in the National Fuel Gas Code, NFPA 54/ANSI Z223.1 -

2002 or the latest edition thereof, to resize the vent system to

approach the minimum size using the appropriate tables in the

appendix of the Code.

9. Return doors, windows, exhaust fans, fireplace dampers and the

remaining appliances to their previous conditions of use after

determining that each appliance remaining connected to the common

venting system is venting properly when tested as outlined above and

the vent system is properly sized.

NOTICE: Common vent sizing of two Category I appliances may be done as

referenced in the National Fuel Gas Code, NFPA 54/ANSI Z223.1 - 2002 or the

latest edition thereof.

3. Condensing in the Chimney

Due to the improved designs, resulting in increasing thermal efficiencies of our

furnaces, more heat is being placed into the home instead of up the chimney.

This means the stack temperature will be lowered, which may result in

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condensing within the chimney under certain conditions. The following is an

explanation on why and what to do if condensing occurs in a chimney or vent.

Moisture (in the form of water vapor) occurs in flue gases when hydrogen is

combined with oxygen during the chemical reaction produced by combustion.

The flue gas water vapor will do one of two things as it escapes up the chimney:

1. Remain in a vapor state, if the internal chimney wall temperature is above

the dew point, or

2. Condense on the chimney walls, if they are chilled below the dew point.

Condensing will always occur on chimney walls whose temperatures are below

the dew point of the flue gas. However, the water may evaporate once the walls

are warmer than the dew point. If the chimney walls do not reach the dew point

during the cycle of the furnace, the moisture may accumulate in large enough

quantities to cause problems such as corrosion of the chimney or corrosion of

the furnace heat exchanger.

This condensation most likely will not occur at the bottom of the chimney,

because the flue gas is heating the chimney walls as it rises and the bottom will

be heated first. This heating of the walls will cause the flue gas temperature to

drop, which in turn may reduce the wall temperature below the dew point causing

condensation to appear on the upper part of the chimney first. This condensation

may drip back as far as the flue pipe and heat exchanger, where corrosion may

occur if not corrected.

To prevent condensation, it is necessary that the internal chimney wall

temperature always be kept above the dew point. The chimney may have to be

lined with a flue liner if the temperature loss is too great for the furnace. A liner

will act as an insulator and reduce the flue gas temperature loss. Insulation may

be added around the liner for further temperature stability. If the chimney is on

the exterior of the home and condensing occurs, the chimney may be insulated

around its exterior to help the flue hold it's temperature. Also, check to see if the

chimney is too large for the flue gases to heat, if so reduce to proper size by

lining. Be sure to use steel liners such as stainless types 430, 304, 316, or for

the toughest against corrosion type 29-4C.

More detailed information on condensing may be obtained from the 2000

ASHRAE systems and Equipment Handbook Chapter 30. Refer to National Fuel

Gas Code, NFPA 54/ANSI Z223.1-2002, or latest edition, Category I venting

tables, for proper vent sizing.

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4. Flue/Vent Connector

• Either drill a starter hole in the inducer or use a self-tapping screw to

mount the flue pipe to the inducer. Failure to follow these instructions

may damage the inducer.

• All vents and vent connectors must fit tightly to avoid air leaks.

• The MHA1/MDA1 series furnaces must not be installed with vent

damper.

The connection of this furnace to the vent system, shall be in accordance with

the local building codes, the vent manufacturers instructions and part 10,”

Venting of Equipment”, of the National Fuel Gas Code, NFPA 54/ANSI Z223.1-

2002, or latest edition.

These venting tables also include venting combinations, which apply to common

venting arrangements of two or more appliances. These requirements as well as

all the installation requirements outlined in this manual for an MHA1/MDA1

series furnace must be followed when an MHA1/MDA1 furnace is common

vented with another Category I gas appliance.

See also Section II, J, 2, of this manual “Replacing an Existing Furnace from a

Common Vent” for information on testing the proper operation of appliances in a

common vent.

The vent connector must be galvanized or stainless steel metal pipe and must be

a 3 in. in diameter for the MHA1/MDA1-50 and 4 in. in diameter for the

MHA1/MDA1-75, MHA1/MDA1-100 and MHA1/MDA1-125. The MHA1/MDA1-75,

MHA1/MDA1-100 and MHA1/MDA1-125 are supplied with a 3 in. to 4 in. adapter

as a transition from the inducer to the 4 in. vent size (see figure 4). No size

reduction is permissible. For minimum and maximum vent lengths, see Venting

Tables for Category I appliances in the National Fuel Gas Code, NFPA 54/ANSI

Z223.1-2002, or latest edition.

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All installations and services must be performed by qualified service personnel.

Figure 4: Vent Connection to Inducer

A self-tapping sheet metal screw and high temperature sealant such as Dow

Corning 736 or General Electric RTV106 (temperature rating 480°F minimum)

should be used to secure both the flue pipe (MHA1/MDA1-50), and the Thermo

Products supplied

in. adapter (MHA1/MDA1-75, MHA1/MDA1-100,

MHA1/MDA1-125) to the outlet of the inducer. If using other than a self-tapping

sheet metal screw to secure the flue pipe to the inducer, a starter hole must be

drilled in the inducer before inserting the screw (refer to Figure 4) to avoid

damage to the inducer housing.

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All installations and services must be performed by qualified service personnel.

When venting the MDA1 series through the blower compartment a vent chute

(AOPS4941) must be used. Refer to Figure 4. This option requires the removal

of the two 4-inch diameter plastic plug from the blower pan and the top panel of

the unit. After removing the plastic plugs, run the 3-inch diameter vent through

the vent chute and the top and bottom openings.

The MDA1-75, MDA1-100 and MDA1-125 will require the use of the 3-inch to 4-

inch adapter provided. This adapter is to be installed after the 3-inch vent exits

the furnace.

The 3-inch diameter vent running through the vent chute must be a continuous

section. No connections should be within the vent chute.

If this venting option is not utilized, the 4-inch diameter plastic plug in the blower

pan and the 3 1/2 inch diameter plastic plug in the top panel of the unit should be

left in place for proper furnace operation.

The flue may exit the unit through the top, left side, or right side of the unit, refer

to Figure 5. The inducer can be rotated by removing the four (4) inducer

mounting screws and rotating the inducer housing. Ensure that inducer gasket is

in place before reinstalling inducer.

Figure 5: Inducer Mounting

All vent connectors connecting the furnace to the vent must be rigidly supported

with hangers and straps in order to prevent sagging and movement after

installation. The vent connector must be supported at a maximum of every four

feet depending on the design and weight of the material used, to maintain

clearances, and to prevent physical damage. The vent pipe must slope upward a

minimum of 1/4" for each foot of horizontal run away from the furnace.

Vent connectors used in connecting the furnace to the vent cannot be channeled

through floors, ceilings, and walls without the proper protective construction. This

construction must be in accordance with the requirements of the National Fuel

Gas Code, NFPA 54/ANSI Z223.1-2002 or the latest edition thereof.

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All installations and services must be performed by qualified service personnel.

It is recommended that all single wall vent connectors connected to the

MHA1/MDA1 Series furnaces have all seams and joints sealed with high

temperature pressure sensitive aluminum tape or high temperature silicone

rubber sealant as noted below.

1. High temperature, aluminum tape, having a temperature rating of 480°F or

greater.

2. Dow Corning 736, General Electric RTV106 sealant, or equivalent, having

a temperature rating of 480°F, or greater.

It is recommended that all vent connectors be insulated with 1.0" thick foil

fiberglass or its equivalent to reduce the chance of condensation and prolong the

life of the venting system. It is mandatory that vent connectors installed in or

passing through an unheated space must be insulated in this manner to prevent

condensate from forming in the connector or vent.

K. Sidewall Venting

• The MHA1/MDA1 Series furnaces SHALL NOT BE COMMON

VENTED IF SIDEWALL VENTING IS EMPLOYED.

• Before sidewall venting the MHA1/MDA1 furnace, read and

understand this section as well as the sidewall vent

manufacturers instructions, which accompany the venting

product. Failure to follow these instructions may cause unsafe

conditions resulting in property damage, personal injury, or loss

of life.

• The sidewall venting system must be installed so as to avoid

possible contact with concealed plumbing or electrical wiring.

• All joints between sections or fittings of the vent system must be

sealed as recommended by the vent manufacturer.

• The proper operation of the vent system and appliance requires

part specified by the vent or appliance manufacturer with no

deletions or substitutions.

The MHA1/MDA1 series furnaces are approved for sidewall venting using only

Field Controls SWGII Power Venter Kit specified below:

Model: SWGII-4HD Power Venter and CK-43F Control Kit

FIELD CONTROLS

2630 AIRPORT ROAD

KINSTON, NC 28504

(252) 522-3031

AUTOMATED LITERATURE FAX: 1-800-385-9460

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All installations and services must be performed by qualified service personnel.

Installation, setup, and operation must be in accordance with the instruction

provided by the manufacture of the power venter. Thermo Products has provided

in the following section maximum and minimum vent lengths guidelines that must

also be followed.

Contact Field Controls for instructions for installing the SWGII vent system

IMPORTANT: No warranty will be made on behalf of the appliance manufacturer

with respect to the sidewall venting system installation or replacement. The

appliance manufacturer shall not be liable for any special, incidental, indirect, or

consequential damages. (Some jurisdictions do not allow exclusion or limitation

of incidental or consequential damages. The above limitations or exclusions may

not apply to you).

IMPORTANT: It is the installer’s responsibility to inform and demonstrate to the

user the correct operation and maintenance of the appliances explained in this

manual, the user’s information manual, and the sidewall vent manufacturer’s

manual.

1. Horizontal Size and Lengths for Horizontal Vents

The minimum sidewall vent length is two (2) feet of straight vent pipe with one (1)

elbow and one (1) adapter or transition to inducer. The maximum vent length and

permitted number of elbows are shown in the following table.

Table 3: Horizontal Size and Length for Sidewall Venting

SIZE

VENT

(In.)

Max. Length of Vent

Pipe (in Feet) With

EQUIVALENT

LENGTH

OF VENT*

(Ft)

MODEL NUMBER

OF FURNACE

ELBOW ELBOWS ELBOWS

MHA1/MDA1-50

MHA1/MDA1-75

MHA1/MDA1-100

MHA1/MDA1-125

* Each elbow used is considered to be equivalent to 5 feet of straight vent pipe.

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L. GAS PIPING

GENERAL GAS PIPING

FIRE OR EXPLOSION HAZARD

• Failure to follow the safety warnings exactly could result in

serious injury, death or property damage.

• Never test for gas leaks with an open flame. Use a commercially

available soap solution made specifically for the detection of

leaks to check all connections.

• Because of the potential of odorant fade, a gas leak may not be

detected by smell. If this furnace is installed below grade, contact

your gas supplier for a gas detector.

• All gas piping must be leak tested using a soap and water

solution (when the gas is turned on) following the procedure

outlined in this section. A final test for gas leakage must be made

after purging the gas line (Refer to Section III, E, of this manual).

This test must be conducted with the unit operating and should

include the furnace piping and gas valve. Never use an open

flame to check for a gas leak.

• Care must be taken not to wet electronic components during leak

test. Wetting the electronic components may damage circuitry

and cause a hazardous situation. Dry moisture from all leads and

terminals if minor wetting occurs. Wait at least 24 hours for the

circuit to fully dry before energizing the burner circuit.

• The furnace and its individual gas shutoff valve must be

disconnected from the gas supply during pressure testing of the

gas supply system at pressures in excess of 1/2 PSIG or 14.0 in.

W.C. The furnace must be isolated from the gas supply by closing

its manual shut off valve at test pressures equal to or less than

1/2 PSIG or 14.0 in. W.C.

• Do not use a connector, which has previously served another gas

appliance.

All gas piping and testing must be performed by a qualified installer or service

person. The installation must comply with local codes, these instructions and the

National Fuel Gas Code, NFPA 54/ANSI Z223.1-2002 or the latest edition

thereof.

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All installations and services must be performed by qualified service personnel.

Piping from the natural gas meter to the furnace shall be in accordance with

requirements of the local utility. Piping from the propane tank to the furnace must

follow the recommendations of the gas supplier.

A readily accessible, design certified manual shut off valve with a non-

displaceable rotor member shall be installed within six feet of the gas equipment

it serves. A union or flanged connection shall be provided downstream from the

manual valve to permit removal of controls. A 1/8" N.P.T. plugged tapping is

provided at the inlet of the gas control for connection of a test gage to check gas

supply pressure to the furnace. Unions must be of a ground joint type or flanged-

jointed using a gasket resistant to LP gas. Pipe dope or sealant certified to be

resistant to the action of liquefied petroleum gases shall be used on all threaded

joints.

Left and Right Gas Supply Piping - This furnace is set up to accept either left or

right side gas piping using a street elbow and a straight pipe.

A sediment trap (drip leg) must be used on both propane and natural gas

installations, to trap oil, condensate and other impurities, which might otherwise

lodge in the gas, valve or plug the burner orifice. The sediment trap shall be

installed as close to the furnace inlet as possible. When there is excessive

condensation between the gas meter and the furnace, a sediment trap shall be

provided at the outlet of the gas meter. Failure to install a sediment trap may void

the limited warranty on the furnace, refer to Fig. 6.

If local codes permit the use of a flexible gas appliance connector, always use a

new listed connector. Do not use a connector, which has previously served

another gas appliance.

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GROUND JOINT

MANUAL GAS

SHUT OFF VALVE

STREET ELBOW

GAS VALVE

SEDIMENT TRAP

₈" N.P.T. MANIFOLD

PRESSURE TAP

5 FT.

NOTE:

ACTUAL UNIT MAY

DIFFER SLIGHTLY

FROM WHAT IS SHOWN.

MHA1 SERIES

Figure 6: Typical Gas Piping

1. INSTALLATION OF NATURAL GAS PIPING

The installation of the gas piping and the following test procedures must be

performed by a qualified installer or service person.

The following chart may be used as a guide in sizing natural gas supply piping.

The input loading of all gas appliances installed on any main or trunk line must

be totaled to determine its required carrying capacity.

EXAMPLE: A line must supply a furnace of 100,000 BTU/hr input, a hot water

heater of 40,000 BTU/hr input and gas range with a 30,000 BTU/hr input

capacity. The total BTU/hr input loading on the line is 170,000 BTU/hr. The

200,000 BTU/hr column on the chart must be used in sizing the pipe.

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TABLE 4: Steel Pipe Size for Natural Gas (IPS)

Burner

Firing Rate,

BTU/Hr

Feet of Pipe From Meter to Burner

50,000

100,000

150,000

200,000

250,000

300,000

1/2

3/4

1/2

3/4

1-1/4

All black pipe sizes shown are nominal iron pipe sizes.

Use black iron steel pipe and malleable iron fittings for natural gas service lines.

Provide rigid supports for the pipe. If the pipe size must be reduced, use

reducing couplings when possible. Avoid the use of reducing bushings. Remove

all burrs and inspect the pipe for dirt or other foreign material prior to connecting.

Maximum supply pressure for natural gas is 14.0 in. W.C. and minimum supply

for purpose of input adjustment is 4.5 in. W.C.

2. INSTALLATION OF PROPANE GAS PIPING

• Copper and brass tubing and fittings (except tin lined) shall not

be used if the gas contains more than a trace (0.3 grains per 100

cubic ft.) of hydrogen sulfide gas. Check with your gas supplier.

Maximum supply pressure for propane gas is 14.0 in. W.C. and the minimum

supply for purpose of input adjustment is 11.0 in. W.C.

Experience has proven that the pressure drop in the gas line running from the

outside propane gas tank to the gas appliances in a home is the most frequent

cause of equipment malfunctions. A single pressure regulator, located at the

tank, will not reliably regulate the high tank pressures (up to 200 PSIG.) down to

11.0 in. W.C. Varying pressures will occur at the appliances as outside

temperatures and usage demands vary. Two-stage regulation is the only

effective method of controlling gas pressure (refer Figure 7).

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Figure 7: Typical Piping For Two-Stage Regulation

NOTICE: Two-stage regulation must be installed for propane gas when used

with any Thermo Pride propane furnace. See illustration above of a typical two

stage piping system.

Table 5: COPPER TUBING SIZE FOR PROPANE GASES

All black pipe sizes shown are nominal iron pipe sizes.

Seamless copper tubing may only be used with gases that are not corrosive to it.

See note below and check with your LP gas supplier before using. Seamless

copper tubing must comply with standard type K or L for seamless copper water

tube, ASTM B 88; or seamless copper tube for air conditioning field service,

ASTM B 280. Copper tubing sizes for indicated BTU input rates are given above

in Table 5.

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M. Electrical

1. Wiring

The furnace must be grounded in accordance with local codes or in

the absence of local codes with the National Electrical Code,

ANSI/NFPA 70-2002, or latest edition.

All wiring shall be performed by a qualified electrician or service person. The

wiring must comply with local codes, the instructions in this manual, and in the

absence of codes with the National Electrical Code, ANSI/NFPA-70, or latest

edition.

Follow these guidelines to complete the wiring portion of the installations.

A separate power supply circuit with over current protection and a disconnect

switch must be provided. The minimum fuse or circuit breaker size is 15 amp.

All electrical components and junction boxes shall be installed in such that they

are protected from water.

All MHA1/MDA1 series furnaces are supplied with a switch box to be mounted

on the outside surface of the right or left side casing. A strain relief bushing is

provided for support of the supply wire harness. Make the 115 volt supply

connection in this junction box. A green screw is provided in order to connect

the power supply ground wire. A disconnect switch can be field mounted on the

2x4 box provided. If not, the disconnect switch must be located reasonably close

to and within sight of the furnace.

NOTICE: The hot surface igniter and operation of this furnace depends on

correct polarity. The hot leg of the supply circuit must be connected to the black

line lead and the common leg to the white line lead in the field mounted junction

box. The hot leg must be connected through the disconnect switch in all cases to

prevent the hazard of electrical shock when servicing.

2. Field Wiring and Replacing Wiring

Field wiring between the furnace and devices not attached to the furnace shall

conform to the temperature limitation for Type T wire [63°F (35°C) rise] when

installed with the manufacturers instructions. If any of the original factory

supplied furnace wiring is replaced, or a separate device other than the

thermostat is wired internal to the unit, 105°C temperature rated thermoplastic

insulated wire or equivalent wire must be used.

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3. Electronic Air Cleaner and Humidifier Connections

The ignition module on this furnace has designated terminals to control the

operation of an electronic air cleaner and/or humidifier. These terminals provide

line voltage for the control of these accessories (See Figure 8).

NOTICE: It is important to confirm that the operating voltage of the humidifier or

EAC being installed matches the output of this control. If not, a field supplied

relay or transformer may be necessary to provide the proper control and supply

voltage for the accessory being installed. See the manufacturers instructions for

the humidifier or EAC for additional requirements.

4. Room Thermostat

A room thermostat is not furnished with this furnace. However, a thermostat is

required to properly operate the furnace control system.

The room thermostat should be located in the natural circulating path of the room

air. The thermostat should not be placed where exposed to cold air infiltration,

i.e. drafts from outside openings such as windows and doors, or where exposed

to air currents from supply or return air registers, or such that natural circulation

of air is blocked, such as behind doors, in shelves, or in corners. It should always

be located on an interior wall.

In addition, the room thermostat should not be exposed to heat from a nearby

fireplace, electrical appliances, lamps, rays from the sun, or mounted directly on

a wall containing warm air ducts, a chimney, or a gas vent. These sources of

heat could adversely affect the operation of the thermostat, preventing it from

properly controlling the room temperature.

Generally, a room thermostat should be set at the lowest temperature that is

comfortable to the building occupants. This will result in the lowest cost to heat

the building.

Proper control of the indoor temperature can only be achieved if the thermostat

is calibrated to the heating and/or cooling cycle. A vital consideration of this

calibration is related to the thermostat heat anticipator.

The proper thermostat heat anticipator setting is 0.8 AMPS for furnace operation

only. To increase length of the heating cycles, increase setting of heat scale; to

decrease length of cycle, decrease setting of heat scale.

Anticipators for the heating operation are of two types, pre-set and adjustable.

Those that are pre-set will not have an adjustment scale and are generally

marked accordingly.

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Anticipators for the cooling operation are generally pre-set by the thermostat

manufacturer and require no adjustment.

5. Blower Motor Speed Wiring

• TURN OFF THE ELECTRICAL POWER to the furnace before

attempting to change blower speed wiring.

The blower motor is factory wired to the ignition control with standard heating

and cooling speeds pre-selected.

When changing motor speeds, simply switch the wire from the needed speed to

either the heating or cooling terminal as applicable on the module to obtain the

desired airflow. The wires for the unused speeds should then be reconnected to

the module in the “park” positions.

GREEN

CAPACITOR

OPTIONAL FAN

DELAY SWITCHES

COMMON (WHITE)

MED-HIGH SPEED (YELLOW)

MED-LOW SPEED (BLUE)

LOW SPEED (RED)

EAC - COMMON

HUMIDIFIER - COMMON

HIGH SPEED (BLACK)

NOTE:

MHA1-50,75,100,125

MDA1-50,100

USE LOW SPEED FOR HEATING

HUMIDIFIER

TRANSFORMER

EAC

TERMINAL COOLING SPEED

MDA1-75,125

USE MED-LOW SPEED FOR HEATING

PARK TERMINALS

FOR UNUSED

SPEEDS

TERMINAL HEATING SPEED

MHA/MDA1-50 HAS A

3 SPEED MOTOR

Figure 8: Blower and Control Panel

The option switches on the W/R integrated control are used to determine the

length of the heat delay-to-fan-on and delay –to-fan-off periods. The following

tables show the time periods that will result from the various switch positions.

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Table 6: Blower delay settings for heating cycles

To delay fan

turn-on by:

15 sec.

Set Switch

Off

30 sec.

*45 sec.

60 sec,

To delay fan

turn-off by:

60 sec.

90 sec.

120 sec.

*180 sec.

Set Switch

#3 #4

Off

*Factory settings for optimal performance

III. Initial Operation of the Furnace:

A. Initial Startup:

• Turn off power to furnace. Before the gas piping system is placed

into service, it must have been leak tested by a qualified heating

contractor. (Refer to the General Gas Piping Requirements section of

this manual regarding the installation and leak testing of gas piping).

• For initial start-up of the appliance after installation, it may be

necessary to purge the air out of the gas line. A qualified heating

contractor should do this. If excessive gas escapes when purging

the gas supply at a pipe union joint, allow the gas to disperse for at

least 15 minutes before attempting to start the appliance. LP gases

are especially dangerous because the specific gravity of LP gases

allows them to accumulate at ground level at possibly explosive

concentrations.

Review the following items before the initial startup. It may be helpful to review

the Sequence of Operations in Appendix B of this manual, also.

a. Check all wiring for loose connections and proper hook-up. Refer to the

connection diagram.

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b. Leak test all field gas piping connections.

c. Check the tubing to the pressure switch to make sure it is snug and

completely seated on the pressure tap.

d. Check to see that the vent terminal is correctly installed and the terminal

openings are clear and free from blockage.

e. Make sure the air filter is in place and relatively clean of dirt and debris.

f. Make sure the thermostat is set in the heating mode of operation.

For Your Safety Read Before Operating:

: If you do not follow these instructions exactly, a fire or

explosion may result causing property damage, personal injury or loss of

life.

This appliance does not have a pilot light. It is equipped with a hot surface

igniter that automatically lights the burner. Do not attempt to light the burner by

hand.

BEFORE OPERATING smell all around the appliance area for gas. Be sure to

smell next to the ground because some gas is heavier than air and will settle on

the ground.

WHAT TO DO IF YOU SMELL GAS

• Do not try to light any appliance.

• Do not touch any electric 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.

Use only your hand to operate the gas control valve knob or, if equipped, the

gas control valve switch. Never use tools. If the knob or lever will not move,

don’t try to repair it, call a qualified service technician. Forced or attempted

repair may result in a fire or explosion.

Do not use this appliance if any part has been under water. Immediately call a

qualified service technician to inspect the appliance and to replace any part of

the control system and any gas control that has been under water.

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Operating Instructions:

STOP! Read the safety information above.

Set the thermostat to the lowest setting.

Turn off all electric power to the appliance.

This appliance is equipped with a hot surface igniter that automatically lights the

burner. Do not try to light the burner by hand.

The burner compartment cover must first be removed before the gas control

valve can be manually operated.

Rotate the gas control valve knob or switch lever to the “OFF” position.

Wait five (5) minutes to clear out any gas. Then smell for gas near the ground. If

you smell gas, STOP! Follow section “h” in the safety information above. If

you don’t smell gas, go to the next step.

Rotate the gas control valve knob or switch lever to the “ON” position.

Replace the burner compartment cover.

Turn on the electric power to the appliance.

Set the thermostat to the desired setting.

If the appliance will not operate, follow the instructions “To Turn Off Gas To

Appliance” and call your service technician or gas supplier.

To Turn Off Gas To Appliance:

Set the thermostat to the lowest setting and set the operating mode switch to

“OFF”.

If service is to be performed, turn off the electrical power to the appliance.

To turn off the gas control valve, remove the burner compartment cover.

Rotate the gas control valve knob or switch lever to the “OFF” position.

Replace the burner compartment cover.

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B. Adjustment Of Heat Input Rate

The main burner gas orifices for this unit were selected based upon the following

assumed characteristic values of the two fuel gases suitable for use with this

appliance design:

a. For natural gas having a higher heating value of 1025 BTU per standard

cubic foot and a specific gravity of 0.60, or

b. For commercial propane gas with a higher heating value of 2500 BTU per

standard cubic foot and a specific gravity of 1.53.

The appliance rating plate inside the burner compartment will specify for which

gas the main burner orifices were selected. If the appliance is installed at an

altitude that is more than 2,000 feet above sea level, it is mandatory that the

input to the burner be reduced 4.0% for every 1,000 feet that it is above sea

level. Example: A furnace installed at an elevation of 5,000 feet, its input must be

reduced 20.0%. At 5000 ft, a total reduction of 5000 ft x 4% per 1000 ft or 20% is

required. This equates to a reduced firing rate of 80,000 BTUH (100,000 BTUH x

0.80 = 80,000 BTUH) at an elevation of 5,000 feet. (If the furnace is installed at

an elevation of 2,000 feet or less, no reduction in input rate is required.)

For high altitude installations, your local gas supplier may assist in determining

the correct main burner orifice size for the elevation at which the appliance is

installed. Our Engineering Department will gladly assist in sizing the orifice if the

lower heating value, in BTU per cubic foot, the specific gravity of the fuel gas,

and the altitude where the appliance will be installed are provided.

To check the input rate of the furnace, allow the unit to operate for 15 minutes

and proceed as follows:

1. Contact your gas supplier and ask for the BTU content (higher heating value)

of one standard cubic foot of the fuel gas supplied to the appliance at the

installation site. If the higher heating values are unavailable, it is reasonable

to assume values of 1025 BTU/cu ft, for natural gas, or 2500 BTU/cu ft, for

commercial propane gas.

2. With all other gas consuming appliances turned off and using a stopwatch,

clock the time required for the (small) dial on the gas meter to make one full

revolution. The meter dial will indicate how many cubic feet pass through the

meter during one revolution, usually one, two or five. The unit must have

been in operation at least 15 minutes before clocking.

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3. The following formula may be used to calculate the heat input rate for the

appliance:

Gas heating value x Amount of gas consumed = Heat input rate, or

Amount of time required to consume the gas

BTU/cu ft x Number of cu ft x 3600 seconds = Input rate (BTU/hr).

Seconds for one revolution x 1 hour

In cases where a gas meter is not installed on the fuel gas supply line, the input

rate can be assumed to be approximately correct if the burner manifold pressure

is the same as that shown on the rating label.

Make sure the gas supply pressure at the appliance falls within the allowable

range for the type of fuel gas. See table 8. The pressure to the furnace must be

checked while the burner, and any other gas appliances, on the same supply

system are operating. Measure the pressure using a pressure gauge, or

manometer, at the 1/8 in. NPT plugged tap on the inlet side of the appliance gas

control valve, shown in the General Gas Piping Requirements section of this

manual. An Allen wrench is normally required to remove the plug from the valve.

Make sure the fuel gas is shut off before removing this plug and installing a

pressure test gage.

Table 8: Allowable Gas Pressures for All MHA1/MDA1 Models

Range of

Supply

Fuel Gas Pressure

(in. W.G.)

Manifold

Pressure

(in. W.G.)

Type of

Natural

14.0 - 4.5

3.5 (± .3)

Propane 14.0 - 11.0 10.0 (±. 3)

This appliance is equipped with multiple, identical, fixed, main burner orifices

sized for the fuel gas and manifold pressure shown on the rating label. The input

rate can only be increased, or decreased, by adjusting the manifold pressure.

To adjust the manifold gas pressure to the main burners:

a. With the gas shutoff, remove the 1/8 in. NPT threaded pipe plug located

on the front side of the main burner gas manifold. Use a U-tube

manometer or pressure gage, capable of measuring pressure in inches of

water column, to measure the gas pressure at this point.

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b. Turn on the fuel gas and cause the appliance to activate the heating

section by answering a “call for heat”.

c. Allow the heating section to operate for 15 minutes.

d. Note the manifold gas pressure.

e. To adjust the pressure, remove the brass screw from the regulator on the

outlet side of the gas control valve. Using a common screwdriver, increase

the manifold pressure by turning the screw inward (clockwise), or

decrease it by turning the screw outward (counterclockwise).

Adjustments to the listed pressure must not exceed 0.3 in. W.G. A

0.3 in. W.G. adjustment will change the input approximately 4.0%.

f. Measure the heat input rate by counting the number of seconds required

for the appliance to consume a specified quantity of gas. Refer to the

preceding procedure to calculate the heat-input rate.

g. If required, repeat the manifold pressure adjustment again. Repeat the

input rate measurement.

h. When the input rate adjustment has been completed, shut off the fuel gas

to the appliance. Remove the pressure gage. Reinstall the manifold pipe

plug using a thread compound resistant to the action of LP gases.

Replace the regulator screw (cap) in the gas valve.

If an input rate within the allowable range cannot be obtained with the present

orifice over the range of manifold pressures given, make sure the gas supply

pressure is within the specified range. If the supply pressure is less than

required, the upstream supply pressure regulator may have to be adjusted to

increase the pressure. If increasing the gas supply pressure fails to provide

adequate gas pressure at the unit, the supply piping may have to be modified to

reduce pressure drop.

C. Burner Adjustment

There are no manual adjustments to the main burners. With the burner

compartment door removed, the flames can be observed. Natural gas flames

should be relatively short in length, have well defined shapes, and are bright light

to deep blue in color, refer to Figure 10.

NOTICE: For appliance operation with propane gas, it is not unusual to

observe mostly blue flames having yellow or yellow-orange tips.

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Figure 10: Typical Observation of Main Burner Flames

If long, rather poorly defined, mostly yellow in color, and nearly opaque burner

flames are observed, this is an indication the quality of combustion is poor.

(Under adverse conditions, black smoke and some sooting may be noticeable as

well.) Some of the causes of poor combustion are, too high an input rate (“over-

firing”), too little or a contaminated supply of combustion air, or a partially

blocked heat exchanger or vent terminal. Should any of these conditions

occur, they must be corrected immediately. Call your qualified heating

contractor for assistance.

D. Setting Supply Air Temperature Rise

All MHA1/MDA1models are designed and wired at the factory for a blower speed

during heating that should result in an approximate temperature rise of 70°F. The

temperature rise through the heating section, for any given blower speed may

vary depending on a number of factors. A few of these factors are, changes in

the actual resistance of the duct system to airflow at any time, de-rating of the

appliance due to elevation, fouling of the heat exchanger surfaces, and changes

in the fuel gas heating value. In general, a lower temperature rise through the

heating section will result in higher heating efficiency.

Temperature rise = supply air temperature - return air temperature.

After 15 to 20 minutes of continuous operation, the temperature rise through the

furnace must fall within a range of 55° to 85° F. If the outlet or supply duct

temperature is too high, check to make sure the return air filter is clean, the

return air registers are free from obstruction, the outlet registers are properly

adjusted and clear, and the supply and return air ducts are open.

The circulating air blower is not moving enough air if the supply air temperature

is still too high. Before proceeding further, turn off the power supply to the

appliance and remove the blower access door. The speed of the blower must be

increased by changing the speed tap from the motor to the next higher tap, refer

to Figure 8.

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E. Checkout Procedure

Before any system of gas piping is finally put into service, it shall be carefully

tested to assure that it is “gas-tight”, as indicated in the General Gas Piping

Requirements section of this manual.

NOTICE: All controls on the unit should be checked for proper functioning

prior to the qualified service personnel leaving the job site. Specifically the

following should be checked:

1. With heating system in normal heating operation, check to make certain

blower will start and stop automatically under control of integrated furnace

control.

2. Check safety limit control as follows:

a. Shut off incoming power.

b. Block return air opening or disconnect blower motor leads.

c. Restore power to appliance.

d. In the heating mode, set the thermostat above room temperature

producing “a call for heat”.

e. When high air temperatures are reached within the furnace, the high limit

control should act to shutdown the main burners.

f. Shut off the electrical power.

IMPORTANT: Remove blockage or reconnect blower motor and

restore power.

3. Make certain the thermostat will automatically start and stop the appliance.

4. Block the vent terminal outlet gradually with a flat piece of metal, until the

pressure switch functions shutting off the main burners.

IMPORTANT: Remove flue blockage when done.

NOTICE: Heat exchanger oil will burn off on initial firing creating an

unpleasant odor. To prevent this odor from occurring more than once, it is

suggested the furnace be allowed to run for 30 minutes, or until odor has

dissipated.

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IV. Troubleshooting

NOTICE: BEFORE TROUBLESHOOTING, FAMILIARIZE YOURSELF WITH

THE START UP AND CHECKOUT PROCEDURE.

ALL INSTALLATION AND SERVICES MUST BE PERFORMED BY QUALIFIED

HEATING CONTRACTORS.

To assist you in troubleshooting this furnace, it is equipped with an integrated

ignition control with diagnostics. These diagnostics evaluate what control system

has experienced a failure and activate a flashing light on the control in different

sequences to help pinpoint the failure which has occurred. Also provided in

appendix C is a troubleshooting flow chart located in the back of this manual.

IMPORTANT: For your convenience, Thermo Products has installed a sight

glass in the blower door of this furnace. The number of flashes in groups should

be observed through this sight glass and recorded before turning off power to the

furnace. Otherwise power to the furnace will be interrupted upon or removing the

blower turning off power or removing the necessary to restart the furnace and

have the failure occur again.

DIAGNOSTIC FEATURES

The 50A65 control used on this furnace continuously monitors its operation and

the operation of the system. If a failure occurs, the LED light on the control will

failure code. If the failure is internal to the control, the light will stay on

continuously. In this case, the entire control should be replaced, as the

control is not field-repairable.

If the sensed failure is in the system (external to the control), the LED will flash in

the following flash-pause sequences to indicate failure status (each flash will last

approximately 0.25 seconds and each pause will last approximately 2 seconds).

1 flash, then pause

2 flashes, then pause

3 flashes, then pause

4 flashes, then pause

6 flashes, then pause

7 flashes, then pause

8 flashes, then pause

Continuous flashing

(no pause)

System lockout

Pressure switch stuck closed

Pressure switch stuck open

Open high limit, aux. limit, or roll-out switch

115 Volt AC power reversed

Low flame sense signal

Check ignitor or improper grounding

Flame has been sensed when no flame should

be present (no call for heat)

The LED will also flash once at power-up.

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V. Dealer Maintenance

SAFETY DURING SERVICING AND INSPECTION

ELECTRICAL SHOCK, FIRE OR EXPLOSION HAZARD

• Failure to follow safety warnings exactly could result in dangerous

operation, serious injury, death or property damage.

• Improper servicing could result in dangerous operation, serious injury,

death or property damage.

• Before servicing, disconnect all electrical power to furnace.

• When servicing controls, label all wires prior to disconnecting. Reconnect

wires correctly.

• Verify proper operation after servicing.

Notice: Homeowner/user routine maintenance

Complete instructions for the homeowner including maintenance procedures,

which must be performed by the homeowner/user, can be found in the "Users

Information Manual."

The following maintenance procedures should be performed at the beginning of

each heating season by a qualified heating contractor. Correct any deficiencies at

once.

A. Electrical

1. Check all wiring for loose connections and any signs of damage or unusual

wear.

2. Check for correct voltage at the furnace when operating.

3. Check amp-draw on blower motor and inducer motor to assure they are not

exceeding nameplate amp rating.

4. Check for correct operation and proper settings (if manually adjustable) of all

controls.

Shut off gas and disconnect power before continuing.

B. General Inspection

1.Inspect the heat exchanger for evidence of corrosion, pitting, warpage,

deterioration, and carbon build-up. Also, look for loose gaskets in the flue pipe,

burner box and accessible areas of the heat exchanger.

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2. Chimney/vent pipe - Vertically vented units - Remove flue pipe from inducer

and inspect for restriction, loose joints, carbon build-up and condensation. Clean

vent and chimney if necessary and replace or repair any degraded vent, vent

connector or chimney damage found. For sidewall vented units refer to the

manufacturer’s maintenance instructions for the sidewall venter.

3. Burners - If it appears that material is accumulating in the burner box the box

and burners can be vacuumed. If necessary, the burners box assembly can be

removed from the separator panel, by removing the screws behind the 1” holes

near the top of the burner box, and the one screw in the flange under the burner

box.

4. Inducer Blower Assembly - Inspect pressure switch tubing connections and

inspect inducer blower/assembly for corrosion, warpage, deterioration and

carbon build-up. If necessary, clean housing and blower wheel with a damp

cloth. Vacuum to remove any lint or dust from motor assembly. The inducer

gasket and the collector box gasket must be replaced if they show any sign of

having been damaged.

5. Clean all furnace markings as necessary and verify that all are still legible. Any

illegible or missing markings must be replaced. Replacements can be obtained

by contacting Thermo Products.

Once all components are cleaned, they must be re-installed to their factory-

produced state. Any seals or joints in the flue system, which have been removed

or loosened, must be reconnected and sealed if necessary. Do this in

accordance with the installation instructions. (Section II, J, of this manual for

vertically vented units, or Section II, K, of this manual for sidewall vented units).

NOTICE: After cleaning the furnace, reference the burner adjustment section of this

manual. Check for operation, proper combustion and no gas leakage according to

the procedure outlined in Section III, of this manual, Burner and Adjustment.

Observe the burner flame illustrations and follow the adjustment procedures if

proper flame(s) are not present.

C. House Air Blower

Check and clean the blower wheel, housing, and compartment with a vacuum.

Check the motor nameplate and follow motor manufacturer instructions for

lubrication, if required.

IMPORTANT: Some motors are permanently lubricated and should not be

oiled. See motor nameplate for specific instructions.

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D. Return Air Filter

The Return Air Filter(s): Provided with this unit is a permanent type filter. This

filter(s) should be inspected and when dirty, cleaned or replaced, if necessary to

assure proper furnace operation. Follow the cleaning, removal and replacement

procedure below.

Filter Maintenance Procedure:

The filter rack will be located between the return air plenum and the return air

opening of the furnace. See Figure 11 for MHA1/MDA1 series units. Slide dirty

filter out of the filter rack. Clean the filter by vacuuming, rinsing with tap water,

hosing or dipping in an ordinary detergent solution. After cleaning, replace the

completely dry filter in the rack. If the filter has a mesh, the mesh side of the filter

must be towards the furnace.

FILTERS

RETURN AIR

SUPPLY AIR

RETURN

AIR

FRONT DOOR

BLOWER

ACCESS

DOOR

COMBUSTIBLE

FLOOR BASE

TYPICAL FILTER

LOCATION

MHA1 SERIES

SUPPLY AIR

MDA1 SERIES

Figure 11: Filter Location

FILTER REPLACEMENT

Should the filter used require replacement, see Table 2 in Section II, I, of this

manual for minimum filter areas required for the different types of filters available

to ensure an adequate replacement is selected.

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IMPORTANT: Remind homeowner of the importance of monthly filter inspections

during operation to ensure maximum efficiency.

VI. Installers Instructions to User

After completing the installation, the installer shall inform and/or demonstrate to

the homeowner:

1. The location of these instructions in the furnace and that these instructions and

the users information manual must be kept along with instructions for any

accessories in the plastic pouch on the inside of the furnace.

2. The location and use of the manual gas shut off valve and furnace electrical

disconnect switch. Instruct user to always shut off gas before shutting off electric

power.

3. The sequence of operation of the furnace.

4. The correct operation and maintenance of the appliance as outlined in the users

information manual.

5. That failure to maintain and operate this furnace in accordance with these

instructions could result in hazardous conditions, bodily injury, and property

damage and may void the limited warranty on the furnace.

6. Review with and encourage the user to read the warnings and instructions

outlined on the front cover and the Safety section of this manual and in the Users

Information Manual.

7. Recommend to the user that a CO detector be installed in the living space with

the use of any fossil fuel burning appliance. The CO Detector should be one that

is design certified by a nationally recognized testing agency.

8. Recommend that the user have a qualified heating contractor inspect the furnace

at the start of each heating season. Inform the user of the frequency of

inspection required for each item in Section IV of the Users Manual.

9. Inform the user to maintain adequate clearances around air openings into the

furnace and not to block or restrict the entrance of air into the furnace area or the

furnace air opening.

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APPENDIX A: SOURCES FOR REFERENCE STANDARDS

1. Air Conditioning Contractors of America

1712 New Hampshire Avenue, NW

Washington, D.C. 20009

(202) 483-9370

2. American Gas Association

Distribution Center

P.O. Box 79230

Baltimore, Maryland 21279-0230

(301) 617-7819

3. American National Standards Institute, Inc.

Attn: Customer Service

11 West 42^ndStreet

New York, New York 10036

(212) 642-4900

4. American Society for Testing and Materials

100 Burr Harbor Drive

West Conshohoken, Pennsylvania 19428-2959

(610) 832-9585

5. American Society of Heating, Refrigeration, and Air-Conditioning Engineers, Inc.

1791 Tullie Circle N.E..

Atlanta, Georgia 30329

(404) 636-8400

6. National Fire Protection Association

1 Batterymarch Park

Quincy, Massachusetts 02269

(800) 344-3555

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APPENDIX B: SEQUENCE OF OPERATIONS

A. Sequence of Operations for Heating System

Mode of Operation

Control System Action

Standby

(At any time the gas

valve is not energized)

Continous safe operation check. If

flame simulation condition present

or roll-out switch opens,system

energizes inducer fan and circulator

blower at high speed until situation

correction occurs.

Start

Thermostat calls for heat,

contacts close

Ignition control module

energized,draft inducer starts.

Pressure switch senses

adequate pressure,

contacts close.

Power is applied to the hot

surface ignitor. Ignitor warms-

up for 20 seconds.

On power interruption, system

shuts off, restarts when

power is restored.

After ignitor warm-up, the

automatic gas control valve

is energized to open.

Start trial for

ignition

If flame is not detected, the

gas valve is de-energized,

the ignitor is turned off and

the ignition control module

goes into the "Retry" sequence.

Flame must be detected

within 4 seconds. If flame

detected, the delay-to-fan-

on time begins (45 seconds)

The retry sequence

provides a 60 second

wait before ignition retry.

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Mode of Operation

Control System Action

After delay-to-fan-on period

ends, circulating air fan is

energized at heating speed.

The (optional) electronic air

cleaner and humidifier are

energized.

Main Burner

Operation

If ignition attempt is unsuccessful,

one more retry will be made before

the ignition control module goes into

system lockout.

Repeated Trials

for Ignition.

If flame is detected,then lost,

the ignition control module will

repeat the initial ignition sequence

for a total of four recycles. After

four unsuccessful recycle attempts,

the control will go into system lockout.

The ignition control module will reset

automatically in 60 minutes.

When thermostat is satisfied,

contacts open and the gas

valve is de-energized. After

proof of flame loss, inducer

and (optional) humidifier are

de-energized. The

Call for Heat

Satisfied

delay-to-fan-off period begins

(180 seconds)

If system is in lockout, try to

reset by interrupting the power

to the furnace at the disconnecting

switch or interrupting the call for heat

at the thermostat. If this does

not restart the system, refer to

the troubleshooting section of

this manual.

System Lockout

After the delay-to-fan-off

period ends, the circulating

air fan and {optional)

electronic air cleaner are

de-energized.

End of Cycle

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APPENDIX C: TROUBLESHOOTING FLOWCHARTS

A. Heating System

Set thermostat subbase to "HEAT".

Does thermostat make contact?

Yes

Is room temperature

above thermostat setting?

Turn thermostat setting

above room temp.

Yes

Is the transformer supplying

24 VAC to the thermostat ?

Replace thermostat.

Are the thermostat wires connected

properly?

Correct wire

connections.

Yes

Check input power,control

system fuse,disconnecting

switch and fuses (if equipped).

Is the control transformer

receiving 120 VAC?

Yes

Replace control transformer.

Is there 24 VAC across

"TH" & "TR" terminals of the

ignition control module.

Is the inducer

blower operating?

Check for continuity

& proper connections

Yes

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Yes

Is there 120 VAC across draft

inducer power terminals "IND"

& "IND N" at the ignition control

module?

Yes

Check wiring to draft inducer.

If okay, replace inducer assembly.

Check the ignition control module

diagnostic LED lamp. Reset the

module by interrupting power to

system for more than one second.

If LED stays on continuously, replace

ignition control module.

After pre-purge,does the

hot surface ignitor energize

and glow?

Is there voltage present at the

hot surface ignitor terminals

"IGN" & "IGN N" at the ignition

control module?

Yes

Check wiring to hot surface

ignitor. If okay, replace hot

surface ignitor assembly.

Check across "MV" terminals

on ignition control module for 24

VAC during the 4 second flame

proving period after ignitor

After hot surface ignitor

warm-up, does gas valve

open?

warm-up. Is there 24 VAC?

Yes

Check wiring to gas valve.

If okay, Replace gas valve.

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Yes

Measure gas supply pressure

at inlet to gas valve. Is it at

least 4.5" W.G. for natural gas

or 11" W.G. for L.P. gases?

After gas valve opens,

do the burners ignite?

Check gas supply. Open all

manual gas control valves

serving the unit.

Yes

Check ignitor voltage.

during 20 second warm-up,

it should be at least 105

VAC.

Correct low line voltage

problem or replace ignition

control module.

Yes

Is ignitor positioned

correctly?

Reposition to

correct location.

Yes

Check for blocked or severely

corroded burners or burner orifices.

Clean or replace as required.

Adjust supply pressure to

4.5" W.G. for natural & 11"

W.G. for LP gases. Adjust

manifold pressure to 3.5" W.G.

for natural gas or 10" W.G. for LP

gases. If gas pressure fluctuates,

a pressure regulator may be

required or gas piping

Yes

Measure supply & manifold

pressures. Are they constant

over time and within the allowable

ranges?

Do burners stay lit

past proof of flame

check?

may be too small for flow.

Check DIP switch settings on

ignition control module against

those on connection diagram.

Is blower still inoperable after

time delay with DIP switches

set correctly?

Yes

Does the ignition control

module energize the circulating

air blower after the 45 second

time delay?

Yes

Measure voltage on the

circulating air blower

terminals "CIR N " &

"HEAT". Is it 120 VAC?

Check wiring to blower. If okay,

replace the ignition control

module.

Yes

Does the circulating

air fan come on

when energized?

Check for blower wheel

rubbing against housing

or motor shaft spinning

freely. Adjust or replace

as necessary.

Does blower wheel

spin freely?

Yes

Is blower motor capacitor

working properly?

Replace blower

motor capacitor

Yes

Replace Motor

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Yes

Does system run until

thermostat is satisfied?

Check all wiring for

loose connections.

Is LED light on ignition

control module flashing?

Yes

If LED Light Flashes:

1 Flash, then pause............System lockout

2 Flashes, then pause........Pressure switch stuck closed

3 Flashes, then pause........Pressure switch stuck open

4 Flashes, then pause........Open high limit, aux. limit, or roll-out switch

6 Flashes, then pause........115 Volt AC power reversed

7 Flashes, then pause........Low flame sense signal

8 Flashes, then pause........Check ignitor or improper grounding

Continuous flashing............Flame has been sensed when no flame

(no pause)

should be present (no call for heat)

Does burner shut off

when thermostat is

satisfied?

Check for short in wire to

thermostat. Replace

thermostat if necessary.

Yes

Does the circulating air

blower turn off after

thermostat is satisfied

within 180 seconds?

Check DIP switch settings

on ignition control module

against those on connection

diagram. Reset if necessary.

Yes

Troubleshooting Complete.

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APPENDIX D: PARTS PACKAGE COMPONENTS

INSTALLATION PARTS PACKAGE

MDA1/MHA1-50(S00S4426)

DESCRIPTION

WIRE NUT

PART NUMBER

300132

QTY.

#8X1/2 TEK SCREWS

for mounting 2X4 J-box

300208

#10-32X1/2 GND SCREW

#10-32 HEX NUT

300109

300110

300270

350024

350020

MG-966

350016

350750

3/16” DIA. STAR WASHER

2X4 J- BOX

2X4 J- BOX COVER

GROUNDING INSTRUCTIONS

HEYCO SR 34-2

HEYCO UB-875

INSTALLATION PARTS PACKAGE

MHA1/MDA1-75(S00S4427)/MDA1/MHA1-100 (S00S4428) / MDA1/MHA1-125

(S00S4429)

DESCRIPTION

WIRE NUT

PART NUMBER

300132

QTY.

#8X1/2 TEK SCREWS

for mounting 2X4 J-box

300208

#10-32X1/2 GND SCREW

#10-32 HEX NUT

300109

300110

300270

350024

350020

MG-966

350016

350750

14310

3/16” DIA. STAR WASHER

2X4 J- BOX

2X4 J- BOX COVER

GROUNDING INSTRUCTIONS

HEYCO SR 34-2

HEYCO UB-875

3” X 4” TAPERED TRANSITION

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APPENDIX E: REPLACEMENT PARTS LIST - MHA1

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REPLACEMENT PARTS LIST - MDA1

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APPENDIX F: WIRING DIAGRAM

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APPENDIX G: MID-EFFICENCY FURNACE SPECIFICATIONS

MID-EFFICIENCY HIGHBOY GAS FURNACE SPECIFICATIONS⁵

Model NO.

MHA1-50

50,000

40,000

MHA1-75

75,000

59,000

MHA1-100

100,000

79,000

MHA1-125

125,000

99,000

Heat input rate (BTUH)

Heating capacity (BTUH)¹

Nominal temp. rise

Heating fan speed

Burner orifice size for nat. gas

Burner orifice size for L.P. gas

AFUE %

70°F

LOW

80.0

17”

LOW

80.0

24”

0.0935” (#42)

0.0591” (1.5 mm)

80.0

44-1/4”

27 ½”

Height of casing

Width of casing

Depth of casing

Warm air outlet²

Return air inlet²

17”

21”

15” x 18”

25” x 16”

131 LBS

15” x 18”

25” x 16”

143 LBS

19” x 18”

25” x 16”

170 LBS

22” x 18”

25” x 16”

186 LBS

Approx. shipping weight

3”

4”

Dia. of flue (vertical vent)

Dia. of flue (sidewall vent)³

CFM @ .2” & .5” W.C. external

static pressure

@HI speed

@MH speed

@ML speed

.2”

.5”

.2”

.5”

.2”

.5”

.2’

.5”

950

860

830

740

1495

1205

920

1335

1125

865

1795

1590

1410

1240

1560

1410

1290

1160

2245

1885

1605

1350

1970

1710

1510

1300

580

440

750

700

@LO speed

Permanent split capacitor, air over, 48 Y

Blower motor type & frame

Blower motor nominal HP

Blower motor full load amps

Motor shaft diameter

1/5

3.25

1/3

6.0

1/2

8.0

3/4

11.0

½”

Clockwise

Direction of rotation (shaft end)

No. of speeds

10 mfd

370 VAC

10-7 R DD

10 mfd

370 VAC

10-9 R DD

10 mfd

370 VAC

10-9 R DD

15 mfd

440 VAC

10-9 R DD

Run capacitor

Blower size

(1) – 1” x 24 ¾” x (1) – 1” x 24 ¾” x (1) – 1” x 24 ¾” x (1) – 1” x 24 ¾”

Size of filters

15 ¾”

x 19 ¾”

Largest recommended air

conditioner⁴

2 Ton

3.5 Ton

4 Ton

5 Ton

115 volts, 60 Hz., 1 phase

Electrical power requirements

Min. Fuse size

15 AMP

20 AMP

ACCESSORY ITEMS

Filter Rack

AOPS 7547

24-1/2” X 15”

AOPS 7547

24-1/2” X 15”

AOPS 7547

24-1/2” X 15”

AOPS 7375

24” X 19”

Flange dimensions²

NOTES:

1. BTU output based on annual fuel utilization efficiency rated by manufacturer.

2. On all outlet and inlet dimensions, the first dimension is width.

3. The MHA1/MDA1 furnaces are approved for sidewall venting using only an approved sidewall power venter. Refer to Side

Wall Venting section of the Installation and service manual provided with the furnace for additional information.

4. To permit largest recommended air conditioning (at .5 static pressure), selection of the highest motor speed is required.

5. All specifications are subject to change without notice.

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All installations and services must be performed by qualified service personnel.

MID-EFFICIENCY COUNTERFLOW / HORIZONTAL GAS FURNACE SPECIFICATIONS⁵

Model NO.

MDA1-50

50,000

40,000

MDA1-75

75,000

60,000

MDA1-100

100,000

81,000

MDA1-125

125,000

101,000

Heat input rate (BTUH)

Heating capacity (BTUH)¹

Nominal temp. rise

Heating fan speed

Burner orifice size for nat. gas

Burner orifice size for L.P. gas

AFUE %

70° F.

LOW

81.0

17”

MD LOW

LOW

MD LOW

81.0

0.0935” (#42)

0.0591” (1.5 mm)

80.0

81.0

44-1/4”

27 ½”

Height of casing

Width of casing

Depth of casing

Warm air outlet²

Return air inlet²

17”

15” x 18”

131 LBS

15” x 18”

143 LBS

19” x 18”

170 LBS

22” x 18”

186 LBS

Approx. shipping weight

3”

4”

Dia. of flue (vertical vent)

Dia. of flue (sidewall vent)³

CFM @ .2” & .5” W.C. external

static pressure

@HI speed

@MH speed

@ML speed

.2”

.5”

.2”

.5”

.2”

.5”

.2’

.5”

900

835

730

680

1400

1200

926

1220

1075

850

1595

1460

1360

1220

1370

1260

1170

1075

2075

1830

1620

1345

1790

1605

1430

1265

580

425

765

700

@LO speed

Permanent split capacitor, air over, 48 Y

Blower motor type & frame

Blower motor nominal HP

Blower motor full load amps

Motor shaft diameter

1/5

3.25

1/3

6.0

1/2

8.0

3/4

11.0

½”

Clockwise

Direction of rotation (shaft end)

No. of speeds

10 mfd

370 VAC

10-9 R DD

10 mfd

370 VAC

10-9 R DD

10 mfd

370 VAC

10-10 R DD

15 mfd

440 VAC

10-10 R DD

Run capacitor

Blower size

(2) –1” x 17 ¾” x (2) –1” x 17 ¾” x (2) – 1” x 17 ¾” x (2) – 1” x 17 ¾”

Size of filters

11 ¾”

13 ¾”

x 17 ¾”

Largest recommended air

conditioner⁴

2 Ton

3 Ton

3.5 Ton

4 Ton

115 volts, 60 Hz., 1 phase

Electrical power requirements

Min. Fuse size

15 AMP

20 AMP

ACCESSORY ITEMS

Combustible Floor Base

Horizontal Plenum Angles

Vent Kit (top vent option)

NOTES:

50DA-BASE

100CA-BASE

125CA-BASE

AOPS4942

AOPS4941

1. BTU output based on annual fuel utilization efficiency rated by manufacturer.

2. On all outlet and inlet dimensions, the first dimension is width.

3. The MHA1/MDA1 furnaces are approved for sidewall venting using only an approved sidewall power venter. Refer to Side

Wall Venting section of the Installation and service manual provided with the furnace for additional information.

4. To permit largest recommended air conditioning (at .5 static pressure), selection of the highest motor speed is required.

5. All specifications are subject to change without notice.

Download from Www.Somanuals.com. All Manuals Search And Download.

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