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

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Carrier 58UHV Installation, Start-up, And Operating Instructions Manual Manual pdf 13 page image

1. Adaptive Heating Mode—Single-Stage Thermostat with2-Stage Heating (See Fig. 13 for thermostat connections.)NOTE: In response to thermostat call for heat R to W/W1, controlselects high-heat heating only with HIGH HEAT ONLY switch(SW1) set to ON regardless of LOW HEAT switch (SW2) setting.With HIGH HEAT ONLY switch set to OFF, LOW HEAT switchselects either low-heat heating only mode when set to ON, or theadaptive heating mode when set to OFF in response to a thermostatcall for heat R to W/W1. (See Tables 6 and 7, and Fig. 15 fordescription of switch settings or Fig. 16 for control circuitdiagram.)This furnace can operate as a 2-stage furnace with a single-stage thermostat because furnace control CPU includes aprogrammed adaptive sequence of controlled operation, whichselects low- or high-gas heat operation. This selection is basedupon the stored history of the lengths of previous gas heatingon/off periods of the single-stage thermostat.The furnace will start up in either low- or high-gas heat. If thefurnace starts up in low-heat, the control CPU determineslow-heat on time (from 0 to 16 minutes) which is permittedbefore switching to high-heat.If power is interrupted, the stored history is erased. When thishappens, the control CPU selects low-heat for 16 minutes andthen switches to high-heat, as long as the thermostat continuesto call for heat. Subsequent selection is based on stored historyof thermostat cycle times.When thermostat calls for heat, R-W/W1 circuit closes. Thefurnace control performs a self-check, verifies that the pres-sure switch contacts for low- and high-heat (LPS and HPS) areopen, and starts motor IDM in low speed or high speed asappropriate.a. Inducer prepurge period—A 15 sec prepurge period beginswhen LPS contacts close. For high-heat operation, bothLPS and HPS must be closed. For low-heat operation, onlyLPS must be closed.b. Igniter warm-up—At end of the prepurge period, the HSI isenergized for a 17-sec igniter warm-up period.c. Trial-for-ignition sequence—When igniter warm-up periodis completed, the main gas valve relay contacts (MGVR-1and -2) (and high-heat pressure switch relay HPSR forhigh-heat operation) close to energize low- and high-heatgas valve solenoid(s) (GV) and humidifier terminal(HUM). The gas valve opens, and 24-v power is suppliedfor a field-installed humidifier at terminals HUM andC OM-24V. The GV permits gas flow to the burners where itis ignited. After 5 sec, the HSI is de-energized, and a 2-secflame-proving period begins.If the HPS fails to close on a call for high-gas heat and LPScloses, the furnace operates at low-heat gas flow rate untilHPS closes.d. Flame-proving—When burner flame is proved at flame-proving sensor electrode (FSE), the control CPU begins theblower-on delay period and continues to hold GV open. Ifburner flame is not proved within 2 sec, the control CPUcloses GV, and the control CPU repeats the ignitionsequence for up to 3 more trials-for-ignition before goingto ignition lockout. The CONTROL TERMINATESLOCKOUT AUTOMATICALLY after 3 hr, or by momen-tarily interrupting 115-v power to furnace, or by interrupt-ing 24-v power at SEC1 or SEC2 to the control CPU (notat W/W1, G, R, etc.). Opening thermostat R-W circuit willnot terminate an ignition lockout.If flame is proved when flame should not be present, thecontrol CPU locks out of gas heating mode and operates IDMon high speed until flame is no longer proved.e. Blower-on delay—If burner flame is proved, 45 sec afterGV is opened BLWM is energized at the appropriateheating airflow: low- or high-heat CFM. Simultaneously,the EAC terminals are energized with 115v and remainenergized as long as BLWM is energized.f. Switching from low- to high-gas heat—If furnace controlCPU switches from low- to high-heat, control CPUswitches the IDM speed from low to high. The high-heatpressure switch relay (HPSR) closes. When IDM providessufficient pressure to close HPS, the high-heat gas valvesolenoid GV is energized. The BLWM switches to high-heat airflow 5 sec after the control CPU switches fromlow-gas heat to high-gas heat.g. Switching from high- to low-gas heat—The control CPUwill not switch from high- to low-gas heat 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 burners, and terminals HUM and C OM 24v arede-energized. The IDM remains energized for a 5 secpost-purge period. The BLWM, which had been operatingat low- or high-heat airflow, will operate at low-heatairflow for 90 sec.Table 6—Setup Switch DescriptionSETUPSWITCH NO.NORMALPOSITIONDESCRIPTIONOF USESW-1Only High-Gas Heat OFF (Staged Gas Heat)Turn switch on to obtain only high-gas-heat operation on any callfor heat regardless of whether R-W/W1, or R-W/W1, -W2 isclosed. SW-1 overrides SW-2.SW-2Low-Gas Heat (Adaptive Mode) OFF (Single-Stage Thermostat)Turn switch off for installations with single-stage thermostats; con-trol selects low-gas-heat or high-gas-heat operation based on pre-vious cycles. Turn switch on for installations with 2-stage thermo-stats to permit only low-gas-heat operation in response to closingR-W/W1. High-gas heat is supplied only when R to W/W1 and W2are closed.SW-3 and SW4 OFF, ON Switches control gas heating mode blower-off delay. (See Table7.)Table 7—Blower-Off Delay SetupSwitch (SW) PositionDESIRED HEATINGMODE BLOWER-OFFDELAY (SEC)SETUP SWITCHSW-3 SW-490 OFF OFF135 OFF ON180 ON OFF225 ON ON13