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

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Carrier 58CVA Installation, Start-up, Operating And Service And Maintenance Instructions Manual pdf 44 page image

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.17. Set thermostat above room temperature and check furnace forproper operation.18. Verify blower airflow and speed changes between heating andcooling.19. Check for gas leaks.Never use a match or other open flame to check for gas leaks.Use a soap-and-water solution. A failure to follow thiswarning could result in fire, personal injury, or death.20. Replace outer access door.Step 3—Sequence of OperationNOTE: Furnace control must be grounded for proper operation orcontrol will lock out. Control is grounded through green/yellowwire routed to gas valve and burner box screw.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, if thethermostat is still calling for gas heating. The amber LED light willflash code 12 during the 90-second period, after which the LEDwill be ON continuous, as long as no faults are detected. After the90-second period, the furnace will respond to the thermostatnormally.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. Single-Stage Thermostat and Two-Stage Heating (Adap-tive mode)See Fig. 22 or 31 for thermostat connectionsNOTE: The low-heat only switch SW1-2 selects either thelow-heat only operation mode when ON, (see item 2. below) or theadaptive heating mode when OFF in response to a call for heat.(See Table 6.) When the W2 thermostat terminal is energized itwill always cause high-heat operation when the R to W circuit isclosed, regardless of the setting of the low-heat only switch.This furnace can operate as a two-stage furnace with a single-stagethermostat because the furnace control CPU includes a pro-grammed adaptive sequence of controlled operation, which selectslow-heat or high-heat operation. This selection is based upon thestored history of the length of previous gas-heating periods of thesingle-stage thermostat.The furnace will start up in either low- or high-heat. If the furnacestarts up in low-heat, the control CPU determines the low-heaton-time (from 0 to 16 minutes) which is permitted before switch-ing 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, andstarts the inducer motor IDM in high-speed.a. Inducer Prepurge Period -If the furnace control CPUselects low-heat operation the inducer motor IDM comesup to speed, the low-heat pressure switch LPS closes, andthe furnace control CPU begins a 15-second prepurgeperiod. If the low-heat pressure switch LPS fails to remainclosed the inducer motor IDM will remain running athigh-speed. After the low-heat pressure switch re-closes thefurnace control CPU will begin a 15-second prepurgeperiod, and continue to run the inducer motor IDM athigh-speed.If the furnace control CPU selects high-heat operation, theinducer motor IDM remains running at high-speed, and thehigh-heat pressure switch relay HPSR is de-energized toclose the NC contact. When sufficient pressure is availablethe high-heat pressure switch HPS closes, and the high-heatgas valve solenoid GV-HI is energized. The furnace controlCPU begins a 15-second prepurge period after the low-heatpressure switch LPS closes. If the high-heat pressure switchHPS fails to close and the low-heat pressure switch LPScloses, the furnace will operate at low-heat gas flow rateuntil the high-heat pressure switch closes for a maximum of2 minutes after ignition.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 contact GVRcloses to energize the gas valve solenoid GV-M. The gasvalve solenoid GV-M permits gas flow to the burnerswhere it is ignited. After 5 seconds, the igniter HSI isde-energized and a 2-second Flame-Proving period begins.If the furnace control CPU selects high-heat operation, thehigh-heat gas valve solenoid GV-HI is also energized.d. Flame-Proving - When the burner flame is proved at theflame-proving sensor electrode FSE, the inducer motorIDM switches to low-speed unless the furnace is operatingin high-heat, and the furnace control CPU begins theblower-ON delay period and continues to hold the gasvalve GV-M open. If the burner flame is not proved withintwo seconds, the control CPU will close the gas valveGV-M, and the control CPU will repeat the ignitionsequence for up to three more Trials-For-Ignition beforegoing to Ignition-Lockout. Lockout will be reset auto-matically after 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/W1, 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 on high speed untilflame is no longer proved.e. Blower-On delay - If the burner flame is proven theblower-ON delay for low-heat and high-heat are as follows:(1.) Low-heat - 45 seconds after the gas valve GV-M isopened the blower motor BLWM is turned ON atlow-heat airflow.(2.) High-heat - 25 seconds after the gas valve GV-M isopened the BLWM is turned ON at high-heat airflow.Simultaneously, the humidifier terminal HUM and elec-tronic air cleaner terminal EAC-1 are energized and remainenergized throughout the heating cycle.f. Switching from Low- to High-Heat - If the furnacecontrol CPU switches from low-heat to high-heat, thefurnace control CPU will switch the inducer motor IDM43→