Carrier 58CTW Installation, Start-up, Operating And Service And Maintenance Instructions

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Carrier 58CTW Installation, Start-up, Operating And Service And Maintenance Instructions Manual pdf 50 page image

5013. Reconnect wires to the following components (Use con-nection diagram on wiring label, if wires were not markedfor reconnection locations.):a. Draft safeguard switch.b. Inducer motor.c. Pressure switches.d. Limit overtemperature switch.e. Gas valve.f. Hot surface igniter.g. Flame--sensing electrode.h. Flame rollout switches.14. Reinstall internal vent pipe, if applicable.15. Reinstall vent connector on furnace vent elbow. Securelyfasten vent connector to vent elbow with 2 field--supplied,corrosion--resistant, sheet metal screws located 180_ apart.16. Replace blower access door only if it was removed.17. Set thermostat above room temperature and check furnacefor proper operation.18. Verify blower airflow and speed changes between heatingand cooling.FIRE OR EXPLOSION HAZARDFailure to follow this warning could result in personalinjury, death, and/or property damage.Never purge a gas line into a combustion chamber. Nevertest for gas leaks with an open flame. Use a commerciallyavailable soap solution made specifically for the detectionof leaks to check all connections. A fire or explosion mayresult causing property damage, personal injury or loss oflife.! WARNING19. Check for gas leaks.Sequence of OperationNOTE: Furnace control must be grounded for proper operationor else control will lock out. Control is grounded throughgreen/yellow wire routed to gas valve and burner box screw.Using the schematic diagram in Fig. 55, follow the sequence ofoperation through the different modes. Read and follow thewiring diagram very carefully.NOTE: If a power interruption occurs during a call for heat(W/W1 or W/W1--and--W2), the control will start a 90--secondblower--only ON period two seconds after power is restored, ifthe thermostat is still calling for gas heating. The amber LEDlight will flash code 12 during the 90--second period, after whichthe LED will be ON continuous, as long as no faults are detected.After the 90--second period, the furnace will respond to thethermostat 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.1. Two--Stage Heating (Adaptive Mode) with Single--StageThermostatSee Fig. 27 -- 34 for thermostat connectionsNOTE: The low--heat only switch SW1--2 selects either thelow--heat only operation mode when ON, (see item 2. below) orthe adaptive heating mode when OFF in response to a call forheat. (See Table 52.) When the W2 thermostat terminal isenergized it will always cause high--heat operation when theR--to--W circuit is closed, regardless of the setting of the low--heatonly switch. This furnace can operate as a two--stage furnace witha single--stage thermostat because the furnace control CPUincludes a programmed adaptive sequence of controlledoperation, which selects low--heat or high--heat operation. Thisselection is based upon the stored history of the length ofprevious gas--heating periods of the single--stage thermostat.The furnace will start up in either low-- or high--heat. If thefurnace starts up in low--heat, the control CPU determines thelow--heat on--time (from 0 to 16 minutes) which is permittedbefore switching to high--heat.If the power is interrupted, the stored history is erased and thecontrol CPU will select low--heat for up to 16 minutes and thenswitch to high--heat, as long as the thermostat continues to call forheat. Subsequent selection is based on stored history of thethermostat cycle times.The wall thermostat “calls for heat”, closing the R--to--W circuit.The furnace control performs a self--check, verifies the low--heatand high--heat pressure switch contacts LPS and HPS are open,and starts the inducer motor IDM in high--speed.a. Inducer Prepurge Period(1.) If the furnace control CPU selects low--heat oper-ation the inducer motor IDM comes up to speed,the low--heat pressure switch LPS closes, and thefurnace control CPU begins a 15--second prepur-ge period. If the low--heat pressure switch LPSfails to remain closed the inducer motor IDM willremain running at high--speed. After the low--heatpressure switch re--closes the furnace control CPUwill begin a 15--second prepurge period, and con-tinue to run the inducer motor IDM at high--speed.(2.) If the furnace control CPU selects high--heat op-eration, the inducer motor IDM remains runningat high--speed, and the high--heat pressure switchrelay HPSR is de--energized to close the NC con-tact. When sufficient pressure is available thehigh--heat pressure switch HPS closes, and thehigh--heat gas valve solenoid GV--HI is ener-gized. The furnace control CPU begins a15--second prepurge period after the low--heatpressure switch LPS closes. If the high--heat pres-sure switch HPS fails to close and the low--heatpressure switch LPS closes, the furnace will oper-ate at low--heat gas flow rate until the high--heatpressure switch closes for a maximum of 2 min-utes after ignition.b. Igniter Warm--Up --At the end of the prepurge period,the Hot--Surface Igniter HSI is energized for a17--second igniter warm--up period.c. Trial--For--Ignition Sequence --When the igniterwarm--up period is completed the main gas valve relaycontact GVR closes to energize the gas valve solenoidGV--M. The gas valve solenoid GV--M permits gasflow to the burners where it is ignited by the HSI. Fiveseconds after the GVR closes, a 2--second flame prov-ing period begins. The HSI igniter will remain ener-gized until the flame is sensed or until the 2--secondflame proving period begins. If the furnace controlCPU selects high--heat operation, the high--heat gasvalve solenoid GV--HI is also energized.d. Flame--Proving -- When the burner flame is proved atthe flame--proving sensor electrode FSE, the inducermotor IDM switches to low--speed unless the furnaceis operating in high--heat, and the furnace control CPUbegins the blower--ON delay period and continues tohold the gas valve GV--M open. If the burner flame isnot proved within two seconds, the control CPU willclose the gas valve GV--M, and the control CPU will