Carrier 58UHV Installation, Start-up, And Operating Instructions Manual

Also see for 58UHV Series: Installation, start-up, and operating instructions User's information manual Installation, start-up, and operating instructions Installation, start-up, and operating instructions

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Carrier 58UHV Installation, Start-up, And Operating Instructions Manual Manual pdf 12 page image

either low- or high-stage. After the 90-sec period, the furnace willrespond 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 ignitor (HSI), and gas valve (GV).1. Adaptive Heating Mode—Single-Stage Thermostat with2-Stage Heating (See Fig. 11 for thermostat connections.)NOTE: In response to thermostat call for heat R to W/W1, thecontrol selects high-stage heating only with HIGH HEAT ONLYswitch (SW1) set to ON regardless of the LOW HEAT switch(SW2) setting. With the HIGH HEAT ONLY switch set to OFF,the LOW HEAT switch selects either the low-stage heating onlymode when set to ON, or the adaptive heating mode when set toOFF in response to a thermostat call for heat R to W/W1. (See Fig.14 for description of switch settings or Fig. 16 for control circuitdiagram.)This furnace can operate as a 2-stage furnace with a single-stage thermostat because the furnace control CPU includes aprogrammed adaptive sequence of controlled operation, whichselects low- or high-stage gas heat operation. This selection isbased upon the stored history of the lengths of previous gasheating on/off periods of the single-stage thermostat.The furnace will start up in either low- or high-stage gas heat.If the furnace starts up in low-stage, the control CPU deter-mines the low-stage on time (from 0 to 16 minutes) which ispermitted before switching to high-stage.If the power is interrupted, the stored history is erased. Whenthis happens, the control CPU selects low-stage for 16 minutesand then switches to high-stage, as long as the thermostatcontinues to call for heat. Subsequent selection is based onstored history of the thermostat cycle times.When the thermostat calls for heat, R-W/W1 circuit closes.The furnace control performs a self-check, verifies that thepressure switch contacts for low- and high-stage (LPS andHPS) are open, and starts the IDM in low speed or high speedas appropriate.a. Inducer prepurge period—A 15 sec prepurge period beginswhen LPS contacts close. For high-stage operation, bothLPS and HPS must be closed. For low-stage operation,only LPS must be closed.b. Ignitor warm-up—At the end of the prepurge period, theHSI is energized for a 17-sec ignitor warm-up period.c. Trial-for-ignition sequence—When the ignitor warm-upperiod is completed, the main gas valve relay contacts(MGVR-1 and -2) (and high-heat pressure switch relayHPSR for high-stage operation) close to energize low-(andhigh-) stage the gas valve solenoid(s) (GV) and thehumidifier terminal (HUM). The gas valve opens, and 24-vpower is supplied for a field-installed humidifier at termi-nals HUM and COM 24V. The GV permits gas flow to theburners where it is ignited. After 5 sec, the HSI isde-energized, and a 2-sec flame-proving period begins.If the HPS fails to close on a call for high-stage gas heat andthe LPS closes, the furnace operates at low-stage gas flow rateuntil the HPS closes.d. Flame-proving—When the burner flame is proved at theflame-proving sensor electrode (FSE), the control CPUbegins the blower-on delay period and continues to holdthe GV open. If the burner flame is not proved within 2 sec,the control CPU closes the GV, and the control CPUrepeats the ignition sequence for up to 3 more trials-for-ignition before going to ignition lockout. The CONTROLTERMINATES LOCKOUT AUTOMATICALLY after 3hrs, or by momentarily interrupting 115-v power to thefurnace, or by interrupting 24-v power at SEC1 or SEC2 tothe control CPU (not at W/W1, G, R, etc.). Opening thethermostat R-W circuit will not terminate an ignitionlockout.If flame is proved when flame should not be present, thecontrol CPU locks out of gas heating mode and operates theIDM on high speed until flame is no longer proved.e. Blower-on delay—If the burner flame is proved, 45 secafter the GV is opened the BLWM is energized at theappropriate heating airflow: low- or high-stage CFM.Simultaneously, the terminals EAC-1 and EAC-2 areenergized with 115v and remain energized as long asBLWM is energized.f. Switching from low- to high-stage gas heat—If the furnacecontrol CPU switches from low- to high-stage, the controlCPU switches the IDM speed from low to high. Thehigh-heat pressure switch relay (HPSR) closes. When theIDM provides sufficient pressure to close the HPS, thehigh-stage gas valve solenoid GV is energized. The BLWMswitches to high-stage airflow 5 sec after the control CPUswitches from low-gas heat to high-gas heat.g. Switching from high- to low-stage gas heat—The controlCPU will not switch from high- to low-stage while thethermostat R-W circuit is closed when a single-stagethermostat is used.h. Blower-off delay—When the thermostat is satisfied, theR-W circuit is opened, the GV is de-energized, stoppinggas flow to the burners, and terminals HUM and C OM 24Vare de-energized. The IDM remains energized for a 5 secpost-purge period. The BLWM, which had been operatingat low- or high-stage airflow, will operate at low-stageairflow for 90 sec.(1.) When in low-stage gas heat and the thermostat issatisfied, the blower will continue to operate at thelow-stage gas heat CFM until the blower-off delayreaches 90 sec. If the blower-off delay switches (onthe 2-stage furnace control) are set for more than 90sec, the blower will operate at the selected continuousfan CFM for the remaining blower-off delay time.(2.) When in high-stage gas heat and the thermostat issatisfied, the blower will continue to operate at thehigh-stage gas heat CFM until the blower-off delayexpires, for all settings of the gas heat blower-offdelay switches on the 2-stage furnace control.i. The furnace control is factory set for a 135-sec blower-offdelay.2. Non-Adaptive Heating Mode—Two-Stage Thermostat and2-Stage Heating (See Fig. 12 for thermostat connections).NOTE: In response to thermostat call for heat R to W/W1 andwith HIGH HEAT ONLY switch SW1 set to OFF, the controlselects low-stage heating only with LOW HEAT switch SW2 setto ON, or the control selects adaptive heating mode with LOWHEAT switch SW2 set to ON. The control selects high-stageheating only with HIGH-HEAT ONLY switch SW1 set to ON. Inresponse to thermostat call for high-stage heat R to W1 and W2,the control selects high-stage heating regardless of switch SW1and SW2 settings. See Fig. 14 for description of switch settings orFig. 16 for control circuit diagram.The start-up and shutdown functions and delays described initem 1. apply to the 2-stage heating mode as well, except forswitching from low- to high-stage and vice versa.12→