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OPEN STANDPIPE FORA/C ORHUMIDIFIERDRAINTEETO OPENDRAINA94054Fig. 46—Example of Field Drain Attachment5. When using field-supplied heat tape, follow heat tape manufacturer’sinstructions for all other installation guidelines.SEQUENCE OF OPERATIONFurnace control must be grounded for proper operation, orcontrol will lock out. Control is grounded throughgreen/yellow wire routed to gas valve and burner box screw.Using schematic diagram, follow sequence of operation throughdifferent modes. (See Fig. 30.) Read and follow wiring diagramcarefully.NOTE: If a power interruption occurs during a call for heat (W),the control will start a 90-second blower-only ON period twoseconds after power is restored, if the thermostat is still calling forgas heating. The red LED light will flash code 12 during the90-second period, after which the LED will be ON continuous, asCONDENSATE TRAPWIRE TIE(S)HEAT TAPE(3 WRAPS MINIMUM)Fig. 47—Condensate Trap Heat TapeA9303634→long as no faults are detected. After the 90-second period, thefurnace will respond to the thermostat normally.The blower door must be installed for power to be conductedthrough the blower door interlock switch ILK to the furnacecontrol CPU, transformer TRAN, inducer motor IDM, blowermotor BLWM, hot-surface igniter HSI, and gas valve GV.Step 1—Heating Mode(See Fig. 27 for thermostat connections.)The wall thermostat ″calls for heat″, closing the R to Wcircuit. The furnace control performs a self-check, verifies thepressure switch contacts PRS are open, and starts the inducermotor IDM.a. Inducer Prepurge Period- As the inducer motor IDMcomes up to speed, the pressure switch contacts PRS close,24 vac power is supplied for a field installed humidifier atthe HUM terminal and the control begins a 15-secondprepurge period.b. Igniter Warm-Up- At the end of the prepurge period, theHot-Surface Igniter HSI is energized for a 17-secondigniter warm-up period.c. Trial-for-Ignition Sequence- When the igniter warm-upperiod is completed the main gas valve relay contacts GVRclose to energize the gas valve GV, the gas valve opens.The gas valve GV permits gas flow to the burners where itis ignited by the Hot Surface Igniter HSI. After 5 seconds,the igniter HSI is de-energized and a 2-second Flame-Proving period begins.d. Flame-Proving- When the burner flame is proved at theflame-proving sensor electrode FSE, the furnace controlCPU begins the blower-ON delay period and continues tohold the gas valve GV open. If the burner flame is notproved within two seconds, the control CPU will close thegas valve GV, and the control CPU will repeat the ignitionsequence for up to three more Trials-For-Ignition beforegoing to Ignition-Lockout. Lockout will be reset automaticallyafter three hours, by momentarily interrupting115 vac power to the furnace, or by interrupting 24 vacpower at SEC1 or SEC2 to the furnace control CPU (not atW, G, R, etc.)If flame is proved when flame should not be present, thefurnace control CPU will lock out of Gas-Heating modeand operate the inducer motor IDM until flame is no longerproved.e. Blower-On Delay- If the burner flame is proven, theblower motor is energized on HEAT speed 66 seconds (040through 120 sizes) or 45 seconds (140 size) after the gasvalve GV is energized.Simultaneously, the electronic air cleaner terminal EAC-1is energized and remains energized as long as the blowermotor BLWM is energized.f. Blower-Off Delay- When the thermostat is satisfied, theR-to-W circuit is opened, de-energizing the gas valve GV,stopping gas flow to the burners, and de-energizing thehumidifier terminal HUM. The inducer motor IDM willremain energized for a 15-second (040 through 120 sizes)or 5-second (140 size) post-purge period. The blower motorBLWM and air cleaner terminal EAC-1 will remain energizedfor 90, 120, 150, or 180 seconds (depending on theblower-OFF delay selection). The furnace control CPU isfactory-set for a 120-second blower-OFF delay.Step 2—Cooling Mode(See Fig. 27 for thermostat connections)Downloaded from www.Manualslib.com manuals search engine
→→The thermostat closes the R-to-G-and-Y circuits. The R-to-Ycircuit starts the outdoor unit, and the R-to-G and Y circuits startthe furnace blower motor BLWM on COOL speed.The electronic air cleaner terminal EAC-1 is energized with 115vac when the blower motor BLWM is operating.When the thermostat is satisfied, the R-to-G-and-Y circuits areopened. The outdoor unit will stop, and the furnace blower motorBLWM will continue operating on the COOL speed for anadditional 90 seconds. Cut jumper J2 to reduce the coolingoff-delay to 5 seconds.Step 3—Continuous Blower ModeWhen the R-to-G circuit is closed by the thermostat, the blowermotor BLWM will operate on continuous-blower speed (same asHEAT speed). Terminal EAC-1 is energized as long as the blowermotor BLWM is energized.During a ″call for heat,″ the blower BLWM will stop during igniterwarm-up (17 seconds), ignition (7 seconds), and blower-ON delay(66 or 45 seconds for 040 through 120 sizes or for 140 size),allowing the furnace heat exchangers to heat up more quickly, thenrestarts at the end of the blower-ON delay period at HEAT speed.In heating, the furnace control CPU will continue running theblower motor BLWM at HEAT speed after the selected blower-OFF delay period is completed.When the thermostat ″calls for cooling″, the blower motor BLWMwill operate at COOL speed. When the thermostat is satisfied, theblower motor BLWM will operate an additional 90 seconds onCOOL speed before reverting back to HEAT speed. Jumper J2 canbe cut to reduce the cooling off-delay to 5 seconds. See Fig. 31.When the R-to-G circuit is opened, the blower motor BLWM willcontinue operating for an additional 5 seconds, if no other functionrequires blower motor BLWM operation.Step 4—Heat Pump ModeWhen installed with a heat pump, the furnace control automaticallychanges the timing sequence to avoid long blower off times duringdemand defrost cycles. When the R-to-W-and-Y or R-to-W-and-Y-and-G circuits are energized the furnace control CPU willcontinue to turn on the blower motor BLWM at HEAT speed, andbegin a heating cycle. The blower motor BLWM will remain onuntil the end of the prepurge period, then shut off for 24 secondsthen come back on at HEAT speed. When the W input signaldisappears, the furnace control begins a normal inducer post-purgeperiod and the blower switches to COOL speed after a 3 seconddelay. If the R-to-W-and-Y-and-G signals disappear at the sametime, the blower motor BLWM will remain on for the selectedblower-OFF delay period. If the R-to-W-and-Y signals disappear,leaving the G signal, the blower motor BLWM will continuerunning the blower motor BLWM at HEAT speed after theselected blower-OFF delay period is completed.Control initiates a 90-sec blower only on period before startinganother heat pump cycle if there is a power interruption. Anytimecontrol senses false flame, control locks out of heating mode. Thisreaction occurs because control ignores W input due to false flamesignal and, as a result, sees only Y input and goes into coolingmode blower off delay. All other control functions remain instandard format.NOTE: EAC-1 terminal is energized whenever blower operates.HUM terminal is only energized when gas valve is energized.Step 5—Component TestCOMPONENT TESTNOTE: The furnace control component test allows all componentsto run for a short time; except the gas valve and humidifierterminal HUM are not energized for safety reasons. The EAC-1terminal is energized when the blower is energized. This featurehelps diagnose a system problem in case of a component failure.Downloaded from www.Manualslib.com manuals search engine35→Fig. 48—Inducer Housing Drain CapFig. 49—Filling Condensate TrapA99118A99119The component test feature will not operate if any thermostatsignal is present ant the control and not until all time delays arecompleted.NOTE: Record the status code BEFORE opening the bloweraccess door and before shutting off power to the furnace. Openingthe blower access door will open the blower door switch and shut
Page 1 and 2: Visit www.carrier.com58MCA4-Way Mul
Page 3 and 4: SAFETY CONSIDERATIONSApplication of
Page 5 and 6: BLOWER SHELFCONDENSATETRAP (INSIDE)
Page 7 and 8: →NOTE: Failure to use CPVC elbows
Page 9 and 10: PLUGCAPAUXILIARY "J" BOXCOLLECTOR B
Page 11 and 12: COMBUSTION - AIRINTAKEVENT5 3 ⁄ 4
Page 13 and 14: This gas furnace may be used for co
Page 15 and 16: APLENUMOPENINGBDFLOOROPENINGCA96283
Page 17 and 18: →supply/outlet or air conditionin
Page 19 and 20: →→→FIRE OR EXPLOSION HAZARDFa
Page 21 and 22: SCHEMATIC DIAGRAM(NATURAL GAS & PRO
Page 23 and 24: →Step 1—Removal of Existing Fur
Page 25 and 26: 12″ MIN12″ MINVENT PIPEVENT PIP
Page 27 and 28: Table 7—Maximum Allowable Pipe Le
Page 29 and 30: ALTITUDE (FT)8001 to 9000‡ALTITUD
Page 31 and 32: ROOF18″ MAXIMUMBRACKETVERTICAL SE
Page 33: AA96128Fig. 41—Rooftop Terminatio
Page 37 and 38: e. Find closest natural gas heat va
Page 39 and 40: U.S.A. OnlyU.S.A. OnlyU.S.A. OnlyTa
Page 41 and 42: U.S.A. and CanadaU.S.A. and CanadaU
Page 43 and 44: BURNERORIFICETable 11—Altitude De
Page 45 and 46: LOAD CALCULATION____________ Heatin
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