Goodman GSM Manual

INSTALLATION & OPERATING
INSTRUCTIONS
for GSM & GSMS
SEALED COMBUSTION
CONDENSING FURNACES
(CATEGORY IV)
WARNING
IF THIS FURNACE IS INSTALLED IN AN ENCLOSED AREA, SUCH AS A GARAGE OR UTILITY
ROOM, WITH ANY OTHER CARBON MONOXIDE PRODUCING DEVICE (i.e. AUTOMOBILE,
SPACE HEATER ETC.) INSURE THAT THE ENCLOSED AREA IS PROPERLY VENTILATED.
WARNING
CARBON MONOXIDE (REFERRED TO AS CO) CAN CAUSE SERIOUS PERSONAL INJURY OR
DEATH
WARNING
THIS FURNACE IS DESIGN CERTIFIED FOR INSTALLATION IN BUILDINGS
CONSTRUCTED ON SITE ONLY.
Goodman Manufacturing Company,L.P.
IO-176A 2550 North Loop West, Suite 400, Houston, TX 77092 12/01
www.goodmanmfg.com

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REPLACEMENT PARTS
Replacement parts for this appliance is available through your contractor or local distributor. For
the location of your nearest distributor consult the white business pages, the yellow page section
of the local telephone book or contact;
SERVICE PARTS DEPARTMENT
GOODMAN MANUFACTURING CO., LP
2550 NORTH LOOP WEST, SUITE 400
HOUSTON, TEXAS 77092
(713) 861 - 2500
The major parts groups are as follows;
BLOWER ASSEMBLY
Motor
Blower housing
Blower wheel
Misc. sheet metal items
Capacitor
HEAT EXCHANGER
Heat exchanger sections
Innerfront
Secondary coil
ELECTRICAL CONTROLS
Control board
Auxiliary / main limit switch
Roll-out switch
Transformer
Door interlock switch
Air pressure switch
Induced draft blower
BURNER ASSEMBLY
Burners
Manifold
Orifices
Gas valve
Ignitor
Flame sensor
MISCELLANEOUS
Wrapper
Access doors
Chimney
Gaskets and seals
Wiring assemblies
To effectively process the parts requirement, the distributor / contractor will need the entire model
number and serial number found on the series and rating plate located inside the blower
compartment.

INDEX
WARNINGS & GENERAL INFORMATION 4
INSTALLATION 5
LOCATION 6, 7
COMBUSTION AIR 7-9
VENTING 9,10
HORIZONTAL THROUGH THE WALL VENTING 11, 12
JOINING PIPE, DRAIN CONNECTIONS 12, 13
GAS PIPING AND GAS PIPE CAPACITY TABLE 13, 14
CIRCULATING AIR SUPPLY, RETURN AIR 15
ELECTRICAL SUPPLY AND CONTROL VOLTAGE CONNECTIONS 16, 17
RATING THE FURNACE 17, 18
TIMING THE GAS METER, MAIN BURNER ADJUSTMENT 18, 19
SAFETY CONTROLS 19 -21
CIRCULATING AIR FILTERS 21
TEMP RISE, SERVICE INSTRUCTIONS 21, 22
SEQUENCE OF OPERATION, REMOVING AN EXISTING APPLIANCE 22 -24
INSPECTING AND CLEANING THE HEAT EXCHANGER 24, 25
BLOWER OFF DELAY, EAC CONTROL, HUMIDIFIER CONTROL 25
WIRING DIAGRAMS 26, 27
LIGHTING INSTRUCTIONS 28
THIS FURNACE CONTAINS ELECTRONIC COMPONENTS WHICH REQUIRE A DEFINITE GROUND. PROVISIONS
ARE MADE FOR CONNECTION OF THE GROUND. IF THIS PRODUCT IS NOT PERMANENTLY AND
POSITIVELYGROUNDED NUMEROUS SERVICE CALLS MAY RESULT. A DEDICATED GROUND FROM THE MAIN
POWER SUPPLY OR AN EARTH GROUND MUST BE PROVIDED.
IO-176
3

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HOUSEHOLD CO ALARMS. CURRENT LIMITATIONS TO THEIR EFFECTIVENESS REQUIRES
THAT YOU OTHERWISE CONTINUE TO FOLLOW APPROPRIATE INSTRUCTIONS LOCATED IN
THE “INSTALLATION & OPERATING INSTRUCTIONS” AND “USERS INFORMATION” MANUALS
RELATING TO PROTECTING PERSONS FROM THE RISKS OF CARBON MONOXIDE. REVIEW
EACH CO MANUFACTURERS’ EXPLANATION OF THEIR UNIT’S CAPABILITIES AND FOLLOW
THOSE INSTALLATION AND OPERATING MANUAL WHEN INSTALLING AND OPERATING
THESE UNITS.
WARNING
THE CIRCULATING AIR DUCTS MUST BE COMPLETELY AND POSITIVELY SEALED TO
PREVENT COMBUSTION PRODUCTS, INCLUDING CARBON MONOXIDE, FROM ENTERING
THE AIR STREAM.
WARNING
TO ENSURE PROPER INSTALLATION AND OPERATION OF THIS PRODUCT, COMPLETELY
READ AND UNDERSTAND THESE INSTRUCTIONS PRIOR TO ATTEMPTING TO ASSEMBLE,
INSTALL, MAINTAIN, OR REPAIR. IF THESE INSTRUCTIONS ARE NOT FOLLOWED PRECISELY
THERE IS A POTENTIAL OF CARBON MONOXIDE POISONING, WHICH CAN RESULT IN
SERIOUS ILLNESS OR DEATH.
WARNING
THIS FURNACE WAS EQUIPPED AT THE FACTORYFOR USE WITH NATURAL GAS ONLY. L.P.
CONVERSION, IF REQUIRED, MUST BE PERFORMED BY A QUALIFIED TECHNICIAN FAMILIAR
WITH PERFORMING THIS TYPE OF CONVERSION. IF L.P. CONVERSION IS REQUIRED, ALL
INSTRUCTIONS INCLUDED WITH THE FACTORY AUTHORIZED KIT MUST BE FOLLOWED. THE
ONLY KIT THAT MUST BE USED FOR THIS CONVERSION IS THE FACTORY AUTHORIZED
LPM-03 (GSM) OR LPM-04 (GSMS). FAILURE TO FOLLOW THOSE INSTRUCTIONS EXPLICITLY
MAY CAUSE FIRE, EXPLOSION, OR PERSONAL INJURY AND PROPERTY DAMAGE.
WARNING
IF PROHIBITED BY LOCAL CODE, DO NOT INSTALL A LIQUID PETROLEUM GAS BURNING
APPLIANCE IN A PIT, BASEMENT, OR SIMILAR LOCATION WHERE, L.P., A HEAVIER THAN AIR
GAS, CAN COLLECT IN LOW AREAS AND MAY NOT DISPERSE NATURALLY. APPLIANCES
SO FUELED SHALL NOT BE INSTALLED IN AN ABOVE GRADE UNDER FLOOR SPACE OR
BASEMENT UNLESS SUCH LOCATION IS PROVIDED WITH APPROVED MEANS FOR
REMOVAL OF UNBURNED GAS.
GENERAL INFORMATION
These Installation and Operating Instructions are intended for use by fully qualified installation
technicians. Some localities require the installer/servicer to be licensed. If in doubt, check with local
authorities. The GSM furnace is a two stage heating appliance. For optimum use, the GSM furnace
should use a two stage room thermostat. The GSMS furnace is a single stage furnace and uses a
single stage room thermostat.

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INSTALLATION: In the USA this furnace MUST be installed in accordance with the latest edition of
the ANSI Z223.1 booklet entitled “National Fuel Gas Code” (NFPA 54), and the requirements or
codes of the local utility or other authority having jurisdiction. In Canada this furnace must be installed
in accordance with the current CAN/ CGA-B149.1 & 2 Gas Installation Codes, local plumbing or
waste water codes and other applicable codes.
ANNUAL inspection of the furnace and it’s vent system are strongly recommended. It is the installer’s
responsibility to inform the user of this importance.
Additional helpful publications are available from the NFPA are, NFPA 90A-Installation of Air
Conditioning and Ventilating System and NFPA90B-Warm Air Heating and Air Conditioning
System. These publications are available from:
National Fire Protection Association, Inc.
Batterymarch Park
Quincy, MA 02269
These furnaces meet the California NOX emission standards and the California efficiency standards.
The GSM & GSMS furnace may be installed as either a Direct Vent or Non-Direct Vent Furnace.
These furnaces are designed to be an UPFLOW or HORIZONTAL furnace. The following sketch
shows a typical installation:
TYPICAL UPFLOW
INSTALLATION
DRAIN
HOSE

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LOCATION
DO NOT install this furnace in a mobile home. This furnace is designed only for installation in
buildings constructed on site and connected to ductwork. When installed in a utility room or closet, the
door should be wide enough to allow the largest part of the furnace to enter, or to permit the
replacement of another appliance, such as a water heater. This furnace is designed to be installed
indoors only. DO NOT install outdoors. This furnace should be installed in such a manner so that it is
protected from water. If any components should become submerged under water, replace those parts
before returning the furnace to operation. DO NOT use as a construction heater. DO NOT install in an
area where freezing can occur without properly protecting the unit and drain system. DO NOT install
in a room designed to be used as a bedroom, bathroom, storage closet, or in any enclosed space
with access only through such room or space. The furnace and it’s individual shut-off must be
disconnected from the gas supply piping system during any pressure testing of that system at test
pressures in excess of 1/2 psig (3.5kPa) The furnace must be isolated from the gas supply piping
system by closing it’s individual manual shut-off valve during any pressure testing of the gas supply
piping system at pressures equal to or less than 1/2 psig (3.5 kPa).
MINIMUM CLEARANCES TO COMBUSTIBLE SURFACES
Unobstructed front clearance of 24” for servicing is recommended.
VENT -0” FRONT -3” RIGHT SIDE-1”
LEFT SIDE-1” REAR -0” TOP OF PLENUM -1”
ACCESSIBILITY CLEARANCE, WHERE GREATER, SHOULD TAKE PRECEDENCE OVER
MINIMUM FIRE PROTECTION CLEARANCE.
A gas fired furnace for installation in a residential garage must be installed so that the ignition source
and burners are located not less than eighteen inches (18”) above the floor and is protected or
located to prevent physical damage by vehicles. A gas furnace must not be installed directly on
carpeting, tile, or other combustible materials other than wood flooring.
WARNING
COMBUSTIBLE MATERIAL MUST NOT BE PLACED ON OR AGAINST THE FURNACE JACKET.
THE AREA AROUND THE FURNACE MUST BE KEPT CLEAR AND FREE OF ALL
COMBUSTIBLE MATERIAL INCLUDING GASOLINE AND OTHER FLAMMABLE VAPORS AND
LIQUIDS. THE USER SHOULD BE CAUTIONED THAT THE FURNACE AREA MUST NOT BE
USED AS A BROOM CLOSET OR FOR ANY OTHER STORAGE PURPOSE.
WARNING
A SOLID BASE PLATE IS SUPPLIED WITH THIS FURNACE AND MUST BE LEFT IN PLACE
WHEN THE FURNACE IS INSTALLED WITH SIDE RETURN DUCTS. FAILURE TO LEAVE THIS
BASE PLATE INSTALLED COULD CAUSE PRODUCTS OF COMBUSTION, INCLUDING
CARBON MONOXIDE, TO BE CIRCULATED INTO THE LIVING SPACE AND CREATE A
POTENTIALLY HAZARDOUS CONDITION, INCLUDING CARBON MONOXIDE POISONING.
REFER TO THE SECTION ON “CIRCULATING AIR SUPPLY” FOR RETURN DUCT
INSTRUCTIONS.

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Before proceeding with this installation check the following;
•Correct clearance from combustible
materials.
•Adequate accessibility for servicing.
•Flooring is not carpet or any other
combustible material, except wood.
•In a garage, the furnace has been
adequately elevated and protected
from vehicle damage.
•Furnace area is free of flammable materials
and vapors such as gasoline.
•Adequate combustion / ventilation air is
supplied.
•Metal base plate is in place when using
side(s) for return air return.
COMBUSTION AIR
The GSM & GSMS furnaces can be installed either as a Direct Vent or a Non-Direct Vent appliance.
If installed as direct vent appliance the combustion air is to be taken from the outdoors via a 2” or 3”
schedule 40 PVC pipe and terminate at the furnace burner box. As a non-direct vent furnace the
combustion air is taken from the area which the furnace is installed. Avoid combustion air sources
which contain flammable fumes and vapors, and gasses such as carbon monoxide, hydrogen sulfide,
ammonia, chlorine, and halogenated hydrocarbons.
Direct Vent Combustion Air. As shown in the following illustration, the combustion air pipe is to
originate at the furnace’s burner box and terminate outside of the building. The diameter of the PVC
combustion air pipe depends upon the furnace size, the length of pipe, and the quantity of fittings
employed. The table found in the “Combustion/Vent Pipe Size” section of this manual outlines these
sizing requirements. As a direct vent installation, the “Air for Combustion and Ventilation Air”
requirements found in ANSI Z223.1, section 5.3 is not required for the furnace to operate correctly.
However, other fuel burning appliances located in the same space as the furnace may still require that
the area be serviced with Combustion and Ventilation Air consistent with ANSI Z223.1, section 5.3.
Non-Direct Vent Combustion Air. If the furnace is to be installed as a non-direct vent appliance,
the combustion air pipeoutlined previously is not used. In lieu of this pipe the 2” or 3” PVC fitting
provided with this furnace is to be attached to the burner box. Also, a debris screen provided with this
furnace is to be cemented into the inlet of the PVC fitting. See thefollowing drawing for details.
Wall
Combustion Air Pipe
PVC Elbow

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As a non-direct vent furnace, this must be installed in accordance with the combustion and ventilation
air requirements found in ANSI Z221.3, section 5.3. When installed as a non-direct vent furnace in an
area which is deemed as a confined area, see (ANSI Z223.1, section 1.7, “Space, Confined”) the
requirements are as follows:
All Combustion Air Taken From The Inside Of The Building. When installed as a non-
direct vent furnace and indoor air is used as the combustion air source, the space is to
be provided with (2) permanent openings communicating directly with an additional
room(s) of sufficient volume so that the combined volume of all spaces meets the
criteria of an unconfined area. The total input of all gas burning equipment shall be
used to determine the minimum size of each opening. Each opening shall be sized to
be a minimum of 1 square inch of free area per 1,000 Btu/hr of combined input of gas
utilization equipment in the area. The minimum area for each opening shall not be less
than 100 square inches, and the minimum dimension of these openings shall not be
less than 3 inches. One opening shall be commence within 12 inches of the top of the
area, while the other opening shall commence within 12 inches of the bottom of the
area.
All Combustion Air Taken From Outdoors. If installed as a non-direct furnace and
outdoor air is selected as the combustion air source, then area shall be serviced with
an opening(s) communicating directly with the outdoors by either of the following two
methods. When calculating the minimum area for each opening the combined input of
all gas utilization equipment is to be considered. Also, the minimum dimension for any
opening shall not be less than 3inches.
Method 1..... Two permanent openings communicating directly with the
outdoors via. horizontal ducts shall be sized to be a minimum
of 1 square inch per 4,000 Btu/hr or,
Two permanent openings communicating directly with the
outdoors via. vertical ducts shall be sized to be a minimum of 1
square inch per 2,000 Btu/hr.
Method 2..... One permanent opening communicating directly with the
outdoors via. a horizontal duct. This opening/duct shall be
sized to be equal to 1 square inch per 3,000 Btu/hr, but not less than
the sum of the areas all of the vent connectors in the confined space.
Debris Screen
s
PVC fitting
Burner Box

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When installed as a direct vent furnace and the unit is notusing the concentric vent kit (CVK-00)
option, the combustion air is to be terminated in the following manner.
If the optional concentric vent kit (CVK-00) is used follow the instructions provided with this accessory.
COMBUSTION AIR / VENT PIPE SIZE
The vent / combustion airpipe system should be of the following sizes.
MODEL #
GSM(S) VENT. DIA. COMB. AIR O ELL 1 ELL 2 ELL 3 ELL 4 ELL
060-33” 2” 100’ 100’ 100’ 100’ 100’
060-32” 2” 75’ 67.5’ 60’ 52.5’ 45’
080-43” 3” 100’ 100’ 100’ 100’ 100’
080-42” 3” 75’ 67.5’ 60’ 52.5’ 45’
100-43” 3” 100’ 100’ 100’ 100’ 100’
VENTING
ANNUAL inspections of the furnace and it’s vent / combustion air supply is strongly recommended. It
is the contractor’s responsibility to inform the user of this importance.
All venting shall be in accordance with Part 7, Venting of Equipment, of the National Fuel Gas Code,
ANSI Z223.1, or applicable local building and / or air conditioning codes.
PROPER INSTALLATION OF THE VENT / COMBUSTION AIR SYSTEMS IS CRITICAL TO SAFE
OPERATION OF THIS APPLIANCE. CAREFULLY READ AND UNDERSTAND THE
INSTRUCTIONS IN THIS SECTION. EACH VENT AND COMBUSTION AIR SUPPLY PIPE MUST
SERVE ONLY ONE APPLIANCE. DO NOT CONNECTTO AN EXISTING VENT OR CHIMNEY.
These furnaces are a condensing type appliance. The products of combustion are recirculated
through a secondary coil. During this process the flue products are brought to a point below dew
point. Thus the moisture present in the flue products condense leaving a liquid by-product. This by-
product must be removed from the furnace and it’s collection system.

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In addition, the vent temperatures are also considerably lower than conventional furnaces. This allows
the use of low temperature plastic as the vent system. The recommended plastic is schedule 40 PVC,
ABS, DWV (or equivalent if allowed by local code). See the previous chart for proper sizing. The use
of two 45oelbows is suggested over the use of a single 90° elbow. The vent pipe must slope toward
the furnace to properly drain the condensate. The drain trap and related parts must be installed as
shown in the illustrations. Failure to follow these instructions can cause products of combustion
including CARBON MONOXIDE entering the dwelling.
IF THIS FURNACE IS INSTALLED IN AN ATTIC OR SIMILAR AREA WHERE CONDENSATE
OVERFLOW MAY BE A PROBLEM, AN AUXILIARY DRAIN PAN MUST BE INSTALLED UNDER
THE FURNACE WITH THE AUXILIARY DRAIN LINES ROUTED TO THE OUTDOORS TO
PREVENT WATER DAMAGE CAUSED BY LEAKS.
THE COMBUSTION PRODUCTS AND MOISTURE IN THE FLUE GASES WILL CONDENSE. THE
CONDENSATE MAY FREEZE ON THE EXTERIOR WALL AND SURROUNDING SURFACES.
SOME DISCOLORATION OR ETCHING IS TO BE EXPECTED.
THE VENT AND COMBUSTION AIR SUPPLY PIPES MUST BE INSPECTED ANNUALLY.
Visually check the vent terminal and combustion air supply pipe screens, clean if necessary.
Visually check for blockage of the condensate disposal system. Hoses may be disconnected to
determine that proper flow is maintained. Should an obstruction be observed, it can be dislodged by
forcing a stream of water through it using a device such as a garden hose.
Materials and procedures must conform to the ASTM Standards.
Pipe and Fittings ASTM 1785, D2465 and D2266
PVC Primer and Solvent Cement ASTM D2564
Procedure for Cementing Joints ASTM D2855 (ref.)
This appliance may be vertically or horizontally vented.
PROTECTION FROM FREEZING The vent pipe and drain assembly must be properly protected
from freezing particularly if it is installed in an UNHEATED SPACE. Low wattage type heaters should
be employed on the drain system. The vent pipe should be insulated using a one (1) inch thick closed
foam insulation if exposed to the outdoors. For pipes located indoors or protected from the elements
such as a garage, basement, etc., fiberglass with an R value of 7 or better is acceptable.
CAUTION
DO NOT install the vent pipe in the same chase with the vent from another fuel burning appliance,
except with a GMN, GMPN, GSM, or GSMS.
DO NOT install the combustion air supply pipe and / or vent pipe under a deck or overhang where
recirculation of combustion products can occur or a positive pressure may exist.
DO NOT install the vent pipe or the combustion air supply pipe within six (6) inches of another fuel
burning appliance.
The drain trap must be easily accessible for checking and / or cleaning. It must be mounted on the
furnace jacket in the holes provided.
DO NOT install the trap higher than the venter blower outlet.
DO NOT install this appliance in any area where freezing may occur without properly protecting the
drain assembly.
CONSULT LOCAL CODES FOR SPECIAL ADDITIONAL REQUIREMENTS.

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HORIZONTAL THROUGH THE WALL VENTING
This appliance may be horizontally vented through an exterior wall following the applicable instructions
in the “VENTING” section in conjunction with these additional requirements.
ALL HORIZONTAL VENT INSTALLATIONS MUST BE MADE IN ACCORDANCE WITH THESE
INSTRUCTIONS.
When selecting which exterior wall to penetrate, the following items should be taken into
consideration:
1. Layout the combustion air and vent system to avoid the possibility of interference with beams,
poles, posts, electricalwiring, plumbing, etc.
2. When possible the combustion air and vent termination should not be subjected to prevailing
winds.
3. The combustion air intake and vent termination must be located at least twelve (12) inches above
expected snowfall. Consideration should be made to past unusual snow falls.
•DO NOT locate the terminal less than seven (7) feet above public walkways. This applies to steps
and stairwells.
•DO NOT locate the termination areas where condensate may present a problem such as flower
beds, patios, etc.
•DO NOT locate within four (4) feet of a gas meter, electric meter, or gas regulator.
•DO NOT locate the vent terminal within four (4) feet of an adjacent building.
•DIRECT VENT INSTALLATION -DO NOT locate the vent terminal within twelve (12) inches of an
operable window or door.
•NON-DIRECT VENT INSTALLATION -DO NOT locate the vent terminal less than (12) inches
above a door or operable window.
•NON-DIRECT VENT INSTALLATION -DO NOT locate the vent terminal less than (4) feet below
or (4) feet horizontally from any door, window or gravity air inlet into any building.
•DO NOT locate the vent terminal less than three (3) feet above, or (10) feet horizontally from, a
forced air inlet into any building, other than the combustion air supply pipe.
•DO NOT locate the vent terminal within three (3) feet of an inside corner of a building or structure.
Minor corners created by fireplace chimneys are excluded from this requirement.
To protect the exterior surface from staining due to the condensate, an aluminum plate or similar
material may be installed surrounding the termination. This plate should extend approximately two (2)
feet from the termination.
WARNING
The area surrounding the vent terminal and combustion air supply pipe must be kept free of snow,
trash, bushes or any other obstacle which may cause a blockage. A blockage can cause
CARBON MONOXIDE to enter the building.

SUPPORTING AND PITCHING THE VENT AND COMBUSTION AIR SUPPLY PIPE
All horizontal runs must be supported at least every five (5) feet and at joints with straps or hangers.
No sags or dips are permitted. The pipes must be saddle supported only. Do not secure the hangers
or straps tightly to the pipes to allow for expansion and contraction of the vent pipe. Maintain a 1/4 “
per foot minimum pitch upward on the horizontal vent pipe from the drain to the
terminal. This will allow the condensate to flow into the drain system and not out the terminal. Vertical
runs must be supported minimum of every six (6) feet.
The combustion air supply pipe should be pitched slightly downward at the inlet to prevent water from
entering the pipe.
JOINING PIPE AND FITTINGS
Follow the instructions accompanying the Cleaner / Primer and Cement.
Observe all cautions printed on the label.
DO NOT CEMENT THE PIPE OR FITTINGS DIRECTLY TO THE VENTER. A RUBBER BOOT AND
HOSE CLAMPS ARE PROVIDED FOR THIS PURPOSE.
CONDENSATE DRAIN
This furnace is designed to remove both sensible and latent heat from the combustion flue gas. As a
result water vapor is condensed in the secondary heat exchanger. This condensate must be drained
either to the outdoors or, where local code permits, to a sewage system. In areas where floor level
drains are not available a condensate pump must be employed. This condensate pump must be
constructed of corrosion resistant materials. It must also have an auxiliary switch which will shut down
the appliance in the event of pump failure or drain tube blockage.
DO NOT run the condensate drain to an outdoor drain or to an unheated area where the possibility of
freezing may occur.

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Note: Some local codes require this condensate to be neutralized prior to disposal.
See illustrations below for proper drain connections.
LEFT DRAIN & VENT RIGHT DRAIN & VENT
HORIZONTAL LEFT HORIZONTAL RIGHT
GAS PIPING & GAS PIPE CAPACITY TABLE
Check the rating plate to make certain that the unit is equipped to burn the type of gas supplied. Care
should be taken after the installation of this appliance that the gas control valve is not subjected to
high gas supply line pressure. In making connections, avoid strains as they may cause noise and
damage the controls. Always use a back-up wrench when tightening the gas supply pipe to the gas
control valve. Check for leaks in the gas supply piping using soap bubbles or other approved method.
NEVER USE AN OPEN FLAME TO CHECK FOR GAS LEAKS. THIS PRACTICE MAY CAUSE A
FIRE, EXPLOSION, BODILY HARM OR PROPERTYDAMAGE.

IO-176 14
All pipe joint compound must be resistant to the action of L.P. gas. When connecting the gas service
to the furnace, install a ground union joint and manual shutoff exterior to the furnace cabinet. This
permits the control assembly to be easily removed. A 1/8” NPT plug on the supply pipe at the manual
valve for the purpose of making pressure measurement must also be installed. The valve should be
readily accessible for turning on or off. A capped drip leg must be installed in the gas supply pipe as
close to the furnace as possible. The drip leg should be installed so that it incorporates a change of
direction.
Refer to local codes or the above mentioned publications for proper location of the manual shutoff
and drip leg lengths. The gas pipe must be sized to eliminate undue pressure drop. See pipe
capacity table or consult your local utility. When checking the manifold pressure, use the pressure tap
located on the gas valve. When checking the service pressure, use the field installed tap located on
the manual shut-off or supply pressure tap located on the gas valve.
All gas piping must conform to local codes, or in the absence of local codes, to the National Fuel Gas
Code ANSI Z223.1 and / or CAN/CGA B149 Installation Codes.
NOTE: Copper tubing must not be used for natural gas installations where more than .3 grains of
hydrogen sulfide per 100 standard cubic feet of gas is present.
For installations in the Commonwealth of Massachusetts see Fuel Gas and Plumbing Code 248
CMR: Appendix C.
Capacity of gas pipe of different diameters and length in ft3/hr, with a pressure drop of 0.3” W.C. and
a specific gravity of 0.60 (natural gas).
*PIPE
SIZE LENGTH OF PIPE IN FEET
10 20 30 40 50 60 70 80
1/2 132 92 73 63 56 50 46 43
3/4 278 190 152 130 115 105 96 90
1 520 350 285 245 215 195 180 170
1 1/4 1050 730 590 500 440 400 370 350
1 1/2 1600 1100 890 760 670 610 560 530
* Nominal size of Iron Pipe in inches.
After the length of pipe has been determined, select the pipe size which will provide the minimum
cubic per hour of gas flow for the required input of the appliance. In the case where more than one
appliance utilizes the same supply pipe be sure to consider the sum of all appliances. The cubic feet
required for the appliances should be determined using the following formula;
Cubic feet of gas required = Gas input of appliance (Btu/hr) / heating value of gas(Btu/hr)
The gas input of the appliance is marked on the specification plate. The heating value of the gas may
be determined by contacting the gas utility or gas supplier. The GSM furnace is a two stage furnace
with the first stage delivering approximately 60% of the total furnace input.

IO-176 15
CAUTION
If the local utility permits the use of a flexible gas connector ALWAYS USE A NEW FLEXIBLE
CONNECTOR. DO NOT USE FLEXIBLE GAS LINES WHICH HAVE SERVICED ANOTHER
APPLIANCE. AFTER A PERIOD OF TIME THESE LINES MAY BECOME BRITTLE AND WITH
THE DISCONNECTION AND RECONNECTION CAN DEVELOP LEAKS.
CIRCULATING AIR SUPPLY AND RETURN AIR
The circulating air supply may be taken from; 1) Outside the building, 2) return ducts from several
rooms, 3) centralreturn, 4) any combination of the above.
When a cooling coil is not installed it is recommended that the supply duct have an access panel so
the heat exchanger can be viewed. This panel shall be of sufficient size to permit the entrance of a
light or probe to assist in the observation of the heat exchanger integrity or sampling the air stream. It
should be sealed to prevent air leakage during normal operation.
CAUTION
DO NOT take return air from bathrooms, kitchens, furnace rooms, garages, utility or laundryrooms or
cold areas. If outside air is utilized it should not be taken from within 10 feet of an appliance vent
outlet, a vent opening or a plumbing drainage system or the discharge from an exhaust system unless
the outlet is three (3) feet above the outside air inlet. DO NOT take return air from areas where it can
pick-up objectionable odors, fumes, or flammable vapors.
Note: When a combination of outdoor and indoor air is utilized the system should be designed and
adjusted such that the temperature reaching the appliance will not drop below 50oF during heating
operation. When this type of system is utilized the volume of air must not be reduced.
Plenum chambers and air ducts must be installed in accordance with the Standard for the Installation
of Air Conditioning and Ventilating Systems, NFPA #90A, or the Standard for the Installation of Warm
Air Heating and Air conditioning Systems, NFPA # 90B. If installed in parallel with a cooling unit the
damper or other means used to control the flow of air must be adequate to prevent chilled air from
entering the furnace, and if manually operated must be equipped with means to prevent operation of
the other unit unless the damper is in the full heat or cool position.
NOTE: UPON INITIAL START-UP SOME SMOKE OR AN ODOR MAY BE PRESENT. THIS IS
NORMAL AND SHOULD DISAPPEAR IN A SHORT AMOUNT OF TIME. IT IS RECOM-
MENDED THAT WINDOWS & DOORS BE OPENED UPON INITIAL START-UP TO VENT THIS
NON-TOXIC SMOKE.
CAUTION
One of the most common causes of problems, including premature heat exchanger failure, in a forced
air heating systems is insufficient return air.
The return air connections to the furnace should be approximately equal to or greater than the area of
the warm air discharge. Consult local codes for specific requirements.
The blower speed should be adjusted to maintain the temperature rise range shown on the rating
plate The total static pressure should not exceed 0.50” W.C.

IO-176 16
WARNING
NEVER ALLOW THE PRODUCTS OF COMBUSTION TO ENTER THE RETURN DUCTWORK OR
CIRCULATING AIR SUPPLY. ALL RETURN DUCTS MUST BE ADEQUATELY SECURED TO THE
FURNACE AND COMPLETELY SEALED. ALL OTHER DUCTWORK MUST BE SECURED WITH
APPROVED CONNECTIONS AND SEALED AIRTIGHT. THE VENT AND COMBUSTION AIR SUPPLY
PIPES MUST BE PROPERLY INSTALLED AND SUPPORTED TO PREVENT LEAKAGE AS NOTED
ELSEWHERE IN THESE INSTRUCTIONS. WHEN A FURNACE IS MOUNTED ON A PLATFORM IT MUST
BE SEALED AIRTIGHT BETWEEN THE FURNACE AND RETURN DUCTWORK. THE FLOOR OR
PLATFORM MUST PROVIDE SOUND PHYSICAL SUPPORT FOR THE FURNACE WITHOUT
CRACKING, GAPS, SAGGING ETC. AROUND THE BASE AS TO PROVIDE A SEAL BETWEEN THE
SUPPORT AND THE BASE. FAILURE TO PREVENT PRODUCTS OF COMBUSTION FROM ENTERING
THE RETURN AIR SUPPLY MAY CAUSE SEVERE ILLNESS OR DEATH FROM CARBON MONOXIDE
POISONING.
Install the return air to terminate through the base under the furnace. For installations where return air
ducts cannot be run under the floor, the return air supply may be taken from the side(s). The solid
bottom supplied on the furnace must remain in place.
WHERE THE MAXIMUM REQUIRED AIR FLOW IS 1800 CFM OR GREATER THE BOTTOM OR
BOTH SIDES MUST BE UTILIZED FOR RETURN AIR SUPPLY. NEVER USE THE REAR OF THE
FURNACE FOR THE RETURN CONNECTION.
WARNING
A SOLID METAL BASEPLATE IS SUPPLIED WITH THIS FURNACE. THIS BASEPLATE MUST BE
IN PLACE WHEN THE FURNACE IS INSTALLED WITH SIDE(S) RETURN AIR DUCTS. FAILURE
TO DO SO MAY PERMIT COMBUSTION PRODUCTS TO ENTER THE LIVING SPACE. THIS MAY
CREATE POTENTIALLY HAZARDOUS CONDITIONS SUCH AS CARBON MONOXIDE
POISONING OR DEATH.
ELECTRICAL SUPPLY CONNECTIONS
The electrical requirements are listed on the series and rating plate on the furnace. A separate supply
line with a current overload device and a manual switch, where required, must be installed. Type “T”
wire or equivalent with a minimum rating of 63oF ( 17oC ) temperature rise must be run directly from
the main power supply to the junction box in the furnace. Copper conductors are required.
Installation of the electricalsupply should be in accordance with local codes. In the absence of local
codes refer to the National Electrical Code ANSI/NFPA No. 70 (latest edition), which can be obtained
from; National FireProtection Association
Batterymarch Park,
Quincy, MA 02269
In Canada refer to the latest edition of the CanadianElectrical Code C22.1 Part I.
WARNING
THE GAS SUPPLY PIPE MUST NEVER USED FOR GROUNDING PURPOSES.

IO-176 17
CONTROL VOLTAGE CONNECTIONS
THERMOSTAT INSTALLATION:
Install the thermostat in accordance with the instructions accompanying the thermostat. Run the
thermostat wires into the control compartment in the furnace. Connect the thermostat wiring as shown
on the wiring diagram. The thermostat wiring should be a minimum of 18 gauge. Adhere to
recommended color code to facilitate future troubleshooting. The thermostat should be located near
the return air grille or opening. It should be approximately 5 feet from the floor level.
Never locate the thermostat where it will be influenced by heat generated from hot water pipes, lamps,
televisions, direct sunlight, supply air registers, etc.
Interconnecting wiring must be secured and protected from damage or disconnection. The use of
solderless connectors or equivalent is recommended.
The low voltage control wiringexiting the furnace is labeled “thermostat wiring”.
SETTING THE HEAT ANTICIPATOR
The following method should be used in measuring the amp draw of the control circuit to assure
proper adjustment of the thermostat heat anticipator.
R
R
Wrap the ‘‘R’’ leg around a
clip-on amp meter 10 times.
Energize the furnace in the
heat mode. Record the reading.
Divide this reading by 10.
Set the heat anticipator on the
thermostat to match this reading.
EXAMPLE:
If the reading on the amp meter is
‘‘4’’, divide this by 10.
The anticipator setting
will be .4 amps.
RATING THE FURNACE
This furnace is shipped from the factory equipped for use with natural gas. The following instructions
are for use with natural gas at altitudes up to 2,000 feet. Should this appliance be converted to L.P.,
refer to the instructions included in the factory authorized L.P. conversion kit LPM-03 (GSM) or LPM-
04 (GSMS). If for use at altitudes in excess of 2,000 feet refer to the instructions included in the
factory authorized high altitude kit (HA-02).
It is important to check and adjust the input rate of the furnace to prevent an overfiring situation.
Overfiring can cause premature heat exchanger failure. The input is controlled by the supply pressure,
orifice size, manifold pressure and heating (calorific) value of the gas. The furnace is supplied with
orifices sized for altitudes up to 2,000 feet using a heating value of approximately 1,000 Btu/hr and
should not normally require change.

IO-176 18
The supply pressure must be measured with this furnace and all other gas burning appliances in
operation. The supply pressure must be adjusted to the pressure range stated on the series and
rating plate. Applications for altitudes in excess of 2,000 feet require an orifice change. The orifices
must be selected using the table below. The furnace de-rate is 4% for each 1,000 feet above sea
level. This table is based upon a heating value of approximately 1,000 Btu/ft3.
The input to the furnace must be checked AFTER reorificing.
For altitudes above 7,000 feet refer to appropriate section of the National Fuel Gas Code, ANSI
Z223.1. To calculate the input of the furnace for installations in altitudes over 2,000 feet use the
following formula;
CORRECTED INPUT = SERIES & RATING PLATE INPUT -(ALTITUDE X .04) X SERIES &
RATING PLATE INPUT / 1000
EXAMPLE:
Corrected input for a 100,000 Btu/hr. appliance installed at an altitude of 6,000 ft. utilizing natural gas
with a heating value of 1,000 Btu/ ft3is determined by-
Corrected Input = 100,000-(6,000 X .04) X (100,000 / 1,000)
Corrected Input = 100,000-(240 X 100)
Corrected Input = 100,000-24,000
Corrected Input = 76,000
Using the orifices sized as shown in the table for 6,000 feet (#48), a meter time of 48.0 seconds is
measured. The actual firing rate of the furnace is
Input = 1,000 (heating value of the gas) X 3600 (constant) / 48.0 (meter time for 1 ft3 of gas)
Input = 3,600,000 / 48.0
Input = 76,000 Btu/hr
In Canada, the series and rating plate input for the furnace apply to installations up to 2,000 feet
(610m) above sea level. Kit HA-02 for natural and L.P. gases is required to convert furnaces from
elevations of 2,000 to 4,500 feet (610m to 1,370m). Canadian certification applies to the installations
of up to 4,500 feet above sea level. Installations above 4,500 feet is subject to acceptance by the
local authorities having jurisdiction.
WARNING
BEFORE ATTEMPTING ANY SERVICE OR ADJUSTMENTS -INSURE THAT THE GAS AND
ELECTRICAL SUPPLIES ARE “OFF”.
ALTITUDE NAT. GAS ORIFICE SIZE
0 -2,000 #45
3,000 #47
4,000 #47
5,000 #47
6,000 #48
7,000 #48

IO-176 19
TIMING THE GAS METER
Use the following method to determine the firing rate of the furnace. The supply pressure tap should
be located on the field installed piping or gas shut-off valve. The manifold pressure tap is located on
the combination gas valve in the furnace and labeled “PRESSURE TAP”.
•Install a manometer graduated in tenths of an inch of water column on the supply pressure tap on
the gas supply pipe.
•Remove the plug at the “Manifold” pressure tap on the gas valve & install a second manometer.
•Determine the size of gas meter used.
•Shut off all other gas fired appliances with the exception of the pilots.
•Adjust the room thermostat.
•Place furnace in operation. The GSM is a two-stage furnace; therefore, both stages are to be
engaged when timing the gas meter.
•Check the supply pressure regulator until the pressure shown on the series and rating plate is
obtained. Adjust if necessary.
•After 15 minutes of operation, time the meter with a stop watch for 2 revolutions and divide by 2.
•Use the appropriate column to determine the furnace input.
•If necessary, adjust the manifold pressure at the gas valve by removing the regulator cap and
turning the adjustment screw clockwise to raise the pressure and counterclockwise to reduce the
pressure. The manifold pressure must be between 3.2” W.C. and 3.8” W.C. for natural gas and 9.5”
W.C. and 10.0” W.C. for L.P.( a field conversion is necessary for L.P.). The inability to obtain the
proper pressure range will require reorificing. After reorificing, repeat the above steps to insure that
the furnace input is adjusted properly.
•Turn off gas and electrical supply, remove manometers and replace any plugs which were removed.
Use a pipe joint compound which is suitable for use with L.P. gas.
•Restore any other appliances affected to their normal operating mode.
METER TIME IN MINUTES AND SECONDS FOR NORMAL INPUT RATING OF FURNACES
EQUIPPED FOR USE WITH NATURAL GAS AT 0-2,000 FEET ALTITUDE.
INPUT
BTU/HR METER SIZE FT3 HEAT VALUE 900
MIN. SEC.
HEAT VALUE
1,000
MIN. SEC.
HEAT VALUE
1040
MIN. SEC.
HEAT
VALUE
1,100
MIN. SEC.
60,000 1
10 0 54 9 00 1 00 10 00 1 03 10 24 1 06 11 00
80,000 1
10 0 41 6 45 0 45 7 30 0 47 7 48 0 50 8 15
100,000 1
10 0 32 5 24 0 36 6 00 0 37 6 14 0 40 6 36
MAIN BURNER ADJUSTMENT
The main burners do notneed adjustment in normal installations.

IO-176 20
SAFETY CONTROL FUNCTIONS AND CHECK-OUT PROCEDURE
GENERAL
In most cases the safety controls are wired is series with the “W” leg. It is imperative that these
switches remain in the circuit. Never jumper, relocate or bypass any control. The proper function of the
safety controls must be checked for proper operation at the time of start-up of the furnace.
WARNING
SHOULD ANY SAFETY CONTROL BE ALTERED, JUMPERED OR BYPASSED, A HAZARDOUS
CONDITION SUCH AS FIRE OR THE POSSIBILITY OF CARBON MONOXIDE ENTERING THE
BUILDING MAY OCCUR.
MAIN LIMIT SWITCH
The main limit switch is a 1/2” disc designed to shut off the burner gas should the outlet (bonnet)
temperature exceed the maximum design outlet air temperature. This switch is not adjustable. To
check the operation, block the return air flow through the unit temporarily. The limit switch should
function and shut the burner gas off within a few minutes. Remove the blockage and allow the switch
to cool sufficiently before reestablishing burner flames.
VENT PRESSURE SWITCH(S)
This furnace utilizes a vent pressure switch(s) which prevents the furnace from operating should any
portion of the vent system become restricted or a venter failure occur. The GSM uses (2) two
individual vent pressure switches. One switch is to control the first stage operation and another for the
second stage operation. To check this switch, place the furnace in operation and remove the hose
from the switch. The burner gas will become extinguished. Replacing the hose will allow the furnace to
operate normally.
COMBUSTION AIR SUPPLY SWITCH
The switch is connected to the combustion box enclosing the burner section of this furnace. It will
function should a restriction occur in the combustion air supply pipe. To check this switch, block the
combustion air supply pipe at it’s termination. The burner gas shouldextinguish.
FLAME SENSOR
Ignition is provided by a hot surface ignition system. The burner flames should be extinguish if the
flame sensor fails to detect the presence of the burner flame. To test , disconnect the flame sensor
wire before placing the furnace in operation. The hot surface igniter should glow and the burners
ignite. However, the burners should shut off after a few seconds of operation. Disconnect the
electrical supply to the furnace, reinstall the disconnected sensor wire and reset the power supply to
restore the furnace to it’s normal operation.
FLAME ROLL-OUT SWITCH
This furnace is equipped with a flame roll-out switch. This manually resetable switch is a 1/2” disc type
and is non-adjustable. This switch is designed to shut down the burner gas in the event that flames
are detected outside the heat exchanger. Should this switch function, contact a qualified service
person to determine the cause of function before resetting. To reset this switch press the button on
top of the switch after the furnace has cooled. To test the operation of the switch with the furnace in
operation, place an open flame on the disc portion of the switch. The switch should function to shut
down the burner gas. Wait until the furnace has cooled sufficiently before resetting the switch.