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M1 Series

Service Manual

M1G and M1M Furnaces

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Summary of Contents for M1G

Page 1: ...M1 Series Service Manual M1G and M1M Furnaces ...

Page 2: ...Typical meters used to service M1 furnaces A Differential Pressure Gauge B Volt Ohm Meter C Manometer D Inclined Manometer A B C D ...

Page 3: ... M1G Troubleshooting flow chart M1G 056 070 15 Troubleshooting flow chart M1G 077 090 16 Sequence of operation heating 17 TROUBLESHOOTING Power supply 17 Transformer 17 On off switch and fan switch 17 Low voltage wiring 18 Limit controls 18 Combustion air relay 077 and 90 only 18 Combustion air blower 077 and 90 only 18 Pressure switch 077 and 90 only 18 Burner assembly 19 Gas valve 20 Pilot assem...

Page 4: ...s is essentially the same with the exception of certain controls which may be unique to each model This manual will deal with all subjects in a general nature i e all text will pertain to all models unless that subject is unique to a particular model or family in which case it will be so indicated It will be necessary for you to accurately identify the unit you are servicing so you may be certain ...

Page 5: ...cal Supply 120 Volts 60 Hz 1 Ph Thermostat Circuit 24 Volts 60Hz 30 VAC Fuse or Breaker 15 Amps Norm Anticipator Setting 0 4 Temperature Rise 45 to 75 F Manifold Pressure Natural Gas 3 5 w c LP Gas 10 w c High Altitude See Table 7 Nominal blower capacity only relay must be field added For Canadian High Altitude 2 000 4 500 reduce the gas manifold pressure to 3 0 w c for natural gas and to 8 w c fo...

Page 6: ...turn air duct system must be at least 352 sq in At least one register should be located whereitisnotlikelytobecoveredbycarpeting boxesand other objects e Materials located in the return duct system must have a flame spread classification of 200 or less This includes a closet door if the furnace is in a closet f Noncombustible pans having 1 upturned flanges are located beneath openings in a floor d...

Page 7: ... Figure 2 if slant deck flashing is used The total length of A B X must be within the minimum and maximum range of one of the Roof Jacks listed in Table 3 ROOF JACK TROUBLE SHOOTING The roof jack assembly is a telescoping type assembly see selection that is made up of a pipe within a pipe construction The inner pipe 5 is for the flue gases to exit the home The outerpipe 8 isusingthespacein between...

Page 8: ...115 volt to the furnace must be supplied from a dedicated circuit containing the correct fuse or circuit breaker for the furnace See Table 5 An electrical switch should be readily accessible from and within sight of the furnace All line voltage connections must be made within the junction box located within the furnace The furnace cabinet must have an uninterrupted unbroken ground to minimize inju...

Page 9: ...tems Once the furnace is installed check the thermostat anticipator against the nominal setting of 0 4 1 Connect the milliamp meter in series with the W circuit 2 Energize a call for heat 3 Read the value of the milliamps 4 Adjust the heat anticipator of the thermostat to the value read on the milliamp meter If the heat anticipator is set too high the furnace may delay in coming on If the heat ant...

Page 10: ...e floor NOTE Shut off valve must be designed and listed for use with liquid petroleum LP gas The gas supply to your home will either be Natural Gas or LP bottle gas Your furnace is factory equipped to operate on Natural Gas If your gas supply is LP you must convert the furnace Thenecessaryinstructionsforthegasconversionare found on the lighting instruction label attached to the furnace in Section ...

Page 11: ...l Gas Code For Canadian high altitude 2 000 4 500 reduce gas manifold pressure to 3 0 W C for natural gas and 9 W C for LP gas NOTE Do not attempt to change the size of an orifice by drilling it out To do so will void the manufacturer s warranty Table 7 High Altitude Derate Figure 8 Convertible Pressure Regulator Cap PRESSURE REGULATOR CAP M11678 N A T N A T L P L P N A T N A T OR OTHER SIDE OF CA...

Page 12: ...ter several tries move the gas control lever to OFF and call your service technician or gas supplier i Move the gas control lever left to ON j Turn on all electric power to the furnace Set the thermo stat to Heat and or the desired temperature setting Set the On Off Fan switch to ON k Replace the furnace door In the event of any flashback or explosion immediately shut off the furnace and call your...

Page 13: ...g Packaged Units Necessary when the Furnace is Used with Some Central Air Conditioners If an air conditioner is installed that does not use the furnace blower for air distribution and that operates independently of the furnace the thermostat system must have an interlock to prevent the furnace and air conditioner fromoperatingatthesametime Thisinterlocksystemusually contains either a Heat Cool swi...

Page 14: ...14 Standing Pilot Model M1G Furnace Sequence of Operation Troubleshooting Wiring Diagrams ...

Page 15: ...lit Relight pilot Consult Pilot Outage Problems in service manual Yes Yes 24 Volts at Gas Valve Lever in ON Position Inlet gas pressure OK Replace Valve Yes Yes 14 second second stage high fire No Yes Yes Air Circulating Blower Starts No Yes Thermostat Satisfies No No Fan Switch closes at 115 Power at Motor Yes Replace Motor No Replace Switch Open R to W Yes Shut down Replace Thermostat Air Circul...

Page 16: ...n and chart Yes Yes 24 Volts at Gas Valve Lever in ON Position Inlet gas pressure OK Replace Valve Yes Yes 14 second second stage high fire No Yes Yes Air Circulating Blower Starts No Yes Thermostat Satisfies No No Fan Switch closes at 115 Power at Motor Yes Replace Motor No Replace Switch Open R to W Yes Shut down Replace Thermostat Air Circulating Blower Shuts Down Yes Stand by for next cycle Fa...

Page 17: ...ary can handle When a transformer is replaced the VA should be at least 30 VA but no more than 40 VA Check out procedure 1 Using a volt ohmmeter on at least 115 vac scale 2 Measure the voltage at the primary side 3 Ifvoltageis115vacmeasurethevoltageatthesecondary terminals marked 24 vac Com on the transformer 4 If115vacismeasuredatprimarybutnovoltageispresent at 24 vac Com replace transformer 5 Fu...

Page 18: ...ft method of combustion air The quantity of air is determined by the inlet orifice ring located on the inlet to the motor assembly Upon a call for heat under normal conditions the combustion blower starts up and supplies combustion air to the chamber If motor does not start check to be sure call for heat is established See troubleshooting flow chart and sequence of operation for further details Th...

Page 19: ...ermocouple cleaningofpilotandburner andinspectingthe heat exchanger the burner assembly must be removed Changing Complete Burner Assembly 1 Gas Line Remove the furnace door then disconnect and remove the gas line from the valve body by using two backup wrenches Be careful not to damage the pipe threads or introduce dirt into the gas line 2 Wiring Leads Remove the two low voltage wiring leads from ...

Page 20: ... thermostat aboveroomtemperaturesothefurnacewillrunthroughout the test procedure g With the furnace operating check for valve staging The operating pressure should be approximately 3 5 WC for Natural Gas 10 WC for LP gas Pilot Assembly Thermocouple and Venturi Burner Thepilotlightsthemainburner Thethermocouplegenerates around 30 MV unloaded unscrewed from valve and around 15 MV loaded screwed into...

Page 21: ... temperature riseandisinserieswiththeheatingspeedoftheaircirculating blower Upon a call for heat and when the burner builds up asupplyofheat thefanswitchwrapsclosedat115 5 and blower motor starts After the thermostat opens and the chamber cools down the fan switch opens at 95 5 and blower shuts off Ifblowerdoesnotstartafterwarmup checkblowerforpower If blower has power see Blower Checkout section ...

Page 22: ...Remove combustion air pipe and combustion blower 5 Remove blower assembly 6 Remove blower deck panel NOTE Panel will be difficult to remove with furnace in alcove 7 Remove front panel NOTE One of the panel screws is located through the combustion air box on the right 8 Lift up divider panel out of side cabinet lances 9 Support the underside of the heat exchanger with a board 10 Remove top collecto...

Page 23: ...re Check sources Plugged pilot orifices Clean or replace orifices 2 Thermocouple burned through Replace thermocouple if defective Millivolts OK Replace gas valve 3 Restricted air inlet or exhaust pipe Clean out any debris No baffle prior to April 1999 Install baffle kit 903722 4 Gas valve not staging Replace gas valve 5 Gas valve closing improperly Replace valve Pilot dirty or needs adjustment Adj...

Page 24: ...BLACK HIGH BLUE MED HI ORANGE MED LO 1 5 2 A C BLOWER RELAY 3 6 4 ON OFF SWITCH GAS VALVE FAN SWITCH HI LIMIT AUX LIMIT TRANSFORMER L1 N C R 24 V 115 V BLACK ORANGE BLUE ORANGE GREEN WHITE WHITE WHITE BLACK GRAY BLUE BLUE BLACK VENT SWITCH BLUE FURNACE ELECTRICAL BOX L1 NEUTRAL GROUND SCREW HEATING COOLING C R G W HEATING COOLING RED RED SEE NOTE TIE WIRE CONNECTOR HOUSING CAP BLUE GRAY 3A FUSE GR...

Page 25: ...UE MED HI ORANGE MED LO WHITE BLOWER MOTOR 4 SPEED 6 5 4 3 2 1 RED LOW BLACK HIGH WHITE CONNECTOR HOUSING CAP SUPPLIED BY INSTALLER Jumper Wire M1GB Units Only Otherwise Hi Speed Connected to Blower Relay GRAY RED GREEN WHITE BLACK BLACK RED BLOWER MOTOR 2 SPEED 7038880 Figure 20 Standing Pilot with Induced Draft Furnace M1GH 077 090 Models 1 5 2 3 6 4 GAS VALVE FAN SWITCH HI LIMIT AUX LIMIT PRESS...

Page 26: ...26 Hot Surface Ignition System Model M1M Furnace Sequence of Operation Troubleshooting Wiring Diagrams ...

Page 27: ...ens Main blower starts after delay time 30 seconds Flame inducer main blower stay on until call for heat ends Replace ignitor Replace circuit board 24 volts at gas valve Insure lever is in ON position Insure gas inlet pressure is below 14 W C Replace gas valve Manifold Gas Pressure Available Burners stay on longer than 6 seconds Check and adjust ignitor gap to 5 16 Will retry 4 more times Soft loc...

Page 28: ...s on for a 30 second post purge period Blower off delay The indoor blower motor is de energized after a 120 second blower off delay Blower timing begins when the thermostat is satisfied COMPONENT PARTS TROUBLESHOOTING Polarity and Ground The furnace will not operate if loss of ground occurs Every effort should be made at the installation to provide a good ground If old 2 wire romex exists it shoul...

Page 29: ...ht will flash 1 M1M Control Board Replacement Replace the control board only after determining a failure has occurred in it Most problems that are blamed on control are actually external to control See troubleshooting section If control has failed use the following procedure to replace 1 Disconnect power to unit by turning off power switch 2 Disconnect molex plugs and all push on terminal connecti...

Page 30: ...trol checks to see if the pressure switch has been openmomentarilywithin2secondspriortotheflameloss If the pressure switch was open any time within the 2 seconds prior to a flame loss the control assumes the flame loss was due to the open pressure switch and responds as described below If the pressure switch opens for more than 1 second after flamehasbeenestablished thecontrolshallde energize theg...

Page 31: ...trollable gas If the control senses the gas valve output as energized when it should be de energized and flame is present the control keeps the inducer motor and indoor blower motor energized until flame is removed Ifthecontroldoesnotsensethatthegasvalveisenergized when it should be the control locks out with the Status LED flashing rapidly CombustionAirBlower AllM1Mmodelsuseacombustion air blower...

Page 32: ... Connect a differential pressure gauge magnehelic or equivalent to the tees The magnehelic connection marked low connects to the lower tee and the one marked high connects to the top tee 3 Start motor 4 Negativepressurecreatedbytheforceddraftmotormust be greater than 0 30 w c for the switch to close 5 Use the ohm meter to check for continuity across the switch 6 If continuity is established switch...

Page 33: ...r and Voltmeter Picture 22 Test Hot Surface Ignitor Figure 24 M1M Burner Assembly Burner Assembly In order to perform procedures such as inspecting for presence of LP gas in chamber cleaning burner andinspectingtheheatexchanger theburnerassem bly must be removed Changing Complete Burner Assembly 1 Gas Line Remove the furnace door then disconnect and remove the gas line from the valve body by using...

Page 34: ...t screw on flat of motor shaft Heat Exchanger Replacement The heat exchanger is the largest and most expensive item in the furnace Before replacing the heat exchanger make certain it is the problem Call the technical service department if you have any uncer tainty about a heat exchanger failure Heat exchangers can become sooted up due to debris in top of furnaces improper conversion or not being c...

Page 35: ...tch is open with inducer on 3 Flashes Pressure switch is closed with inducer off 4 Flashes Lockout due to failed ignition 5 Flashes 115 vac neutral reversed or no ground CONTROL LIGHTS RED Jumper must be removed if converting to a multispeed blower Jumper is required for M1MA models and M1MB 077 090 BLACK WHITE WHITE BLACK BLACK GREEN RED GRAY WHITE BLACK HIGH RED LO WHITE RED LO BLACK HIGH BLUE M...

Page 36: ... After a 45 second pre purge the igniter is energized 3 After a 30 second heat up the gas valve is energized The igniter remains on during the first 6 seconds Gas valve will be de energized at 7 seconds if flame is not proved 4 After 30 seconds the main blower is energized Total elapsed time 105 seconds Normal Shut Down 1 Break R to W circuit 2 After 30 seconds the inducer is turned off 3 After 90...

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