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

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Carrier 58MVP Installation, Start-up, And Operating Instructions Manual Manual pdf 39 page image

humidifier terminal HUM. The inducer motor IDM willremain energized for a 15-second post-purge period. Theblower motor BLWM and air cleaner terminal EAC-1 willremain energized at low-heat airflow or transition to low-heatairflow for 90, 120, 150, or 180 seconds (depending onselection at blower-OFF delay switches). The furnace controlCPU is factory-set for a 120-second blower-OFF delay.TWO-STAGE THERMOSTAT AND TWO-STAGE HEATINGSee Fig. 60 for thermostat connectionsNOTE: In this mode, the low-heat only switch SW1-2 must beON to select the low-heat only operation mode in response toclosing the thermostat R-to-W1 circuit. Closing the thermostatR-to-W1-and-W2 circuits always causes high-heat operation, re-gardless of the setting of the low-heat-only switch.The wall thermostat ″calls for heat″, closing the R to W1 circuit forlow-heat or closing the R to W1-and-W2 circuits for high-heat.The furnace control performs a self-check and verifies the low-heat and high-heat pressure switch contacts LPS and HPS areopen.The start-up and shutdown functions and delays described in item1. above apply to 2-stage heating mode as well, except forswitching from low- to high-heat and vice versa.1. Switching From Low- To High- Heat-If the thermostat R toW1 circuit is closed and the R to W2 circuit closes, the furnacecontrol CPU will de-energize the high-heat pressure switchrelay HPSR to close the NC contact and slowly increase theinducer motor speed until the high-heat pressure switch HPScloses. When the high-heat pressure switch closes, the high-heat gas valve solenoid GV-HI is energized and the inducermotor RPM is noted by the furnace control CPU. The RPM isused to evaluate vent system resistance. This evaluation isthen used to determine the required RPM necessary to operatethe inducer motor in high-heat mode. The blower motorBLWM will transition to high-heat airflow five seconds afterthe R to W2 circuit closes.2. Switching From High- To Low- Heat- If the thermostat R toW2 circuit opens, and the R to W1 circuit remains closed, thefurnace control CPU will energize the high-heat pressureswitch relay HPSR to open the NC contact and slowlydecrease the inducer motor speed to the required low-heatRPM. When the high-heat pressure switch HPS opens, thehigh-heat gas valve solenoid GV-HI is de-energized. Whenthe inducer motor IDM reduces pressure sufficiently, thehigh-heat pressure switch HPS will open. The gas valvesolenoid GV-M will remain energized as long as the low-heatpressure switch LPS remains closed. The blower motorBLWM will transition to low-heat airflow five seconds afterthe R to W2 circuit opens.COOLING MODEThe thermostat “calls for cooling”1. Single-Speed Cooling(See Fig. 28 for thermostat connections.)The thermostat closes R-to-G-and-Y circuits. The R-to-Ycircuit starts the outdoor unit, and R-to-G-and-Y/Y2 circuitsstart the furnace blower motor BLWM on cooling airflow.Cooling airflow is based on the A/C selection shown in Fig.50.The electronic air cleaner terminal EAC-1 is energized with115-v when blower motor BLWM is operating.When the thermostat is satisfied, the R-to-G-and-Y circuits areopened. The outdoor unit will stop, and furnace blower motorBLWM will continue operating at cooling airflow for anadditional 90 sec. Jumper Y/Y2 to DHUM to reduce thecooling off-delay to 5 seconds. (See Fig. 32.)2. Single-Stage Thermostat and Two-Speed Cooling (Adap-tive Mode)(See Fig. 61 for thermostat connections.)This furnace can operate a two-speed cooling unit with asingle-stage thermostat because the furnace control CPUincludes a programmed adaptive sequence of controlled op-eration, which selects low-cooling or high-cooling operation.This selection is based upon the stored history of the length ofprevious cooling period of the single-stage thermostat.NOTE: The air conditioning relay disable jumper ACRDJ mustbe connected to enable the adaptive cooling mode in response to acall for cooling. (See Fig. 32.) When in place the furnace controlCPU can turn on the air conditioning relay ACR to energize theY/Y2 terminal and switch the outdoor unit to high-cooling.The furnace control CPU can start up the cooling unit in eitherlow- or high-cooling. If starting up in low-cooling, the furnacecontrol CPU determines the low-cooling on-time (from 0 to 20minutes) which is permitted before switching to high-cooling.If the power is interrupted, the stored history is erased and thefurnace control CPU will select low-cooling for up to 20minutes and then energize the air conditioning relay ACR toenergize the Y/Y2 terminal and switch the outdoor unit tohigh-cooling, as long as the thermostat continues to call forcooling. Subsequent selection is based on stored history of thethermostat cycle times.The wall thermostat ″calls for cooling″, closing the R toG-and-Y circuits. The R to Y1 circuit starts the outdoor uniton low-cooling speed, and the R to G-and-Y1 circuits startsthe furnace blower motor BLWM at low-cooling airflowwhich is the true on-board CF selection as shown in Fig. 50.If the furnace control CPU switches from low-cooling tohigh-cooling, the furnace control CPU will energize the airconditioning relay ACR. When the air conditioning relay ACRis energized the R to Y1-and-Y2 circuits switch the outdoorunit to high-cooling speed, and the R to G-and-Y1-and-Y/Y2circuits transition the furnace blower motor BLWM to high-cooling airflow. High-cooling airflow is based on the A/Cselection shown in Fig. 50.NOTE: When transitioning from low-cooling to high-cooling theoutdoor unit compressor will shut down for 1 minute while thefurnace blower motor BLWM transitions to run at high-coolingairflow.The electronic air cleaner terminal EAC-1 is energized with115 vac whenever the blower motor BLWM is operating.When the thermostat is satisfied, the R to G-and-Y circuit areopened. The outdoor unit stops, and the furnace blowerBLWM and electronic air cleaner terminal EAC-1 will remainenergized for an additional 90 seconds. Jumper Y1 to DHUMto reduce the cooling off-delay to 5 seconds. (See Fig. 32.)3. Two-Stage Thermostat and Two-Speed Cooling(See Fig. 60 for thermostat connections)NOTE: The air conditioning relay disable jumper ACRDJ mustbe disconnected to allow thermostat control of the outdoor unitstaging. (See Fig. 32.)The thermostat closes the R to G and-Y1 circuits for low-cooling or closes the R to G and-Y1-and-Y2 circuits forhigh-cooling. The R to Y1 circuit starts the outdoor unit onlow-cooling speed, and the R to G-and-Y1 circuit starts thefurnace blower motor BLWM on low-cooling airflow which isthe true on-board CF selection as shown in Fig. 50. The R toY1-and-Y2 circuits start the outdoor unit on high-cooling39