Carrier 59CU5A Installation, Start-up, Operating And Service And Maintenance Instructions

59CU5A: Installation, Start-up, Operating and Service and Maintenance InstructionsManufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.63b. When the R-to-Y/Y2 circuit is closed, R-to-G circuit is open, andthere is a demand for dehumidification, the furnace blower motorBLWM will drop the blower airflow to 65 percent ofhigh-cooling airflow for a maximum of 10 minutes each coolingcycle or until the R-to-G circuit closes or the demand fordehumidification is satisfied. High-cooling airflow is based onthe A/C (air conditioning) selection shown in Fig. 65.c. When the “call for cooling” is satisfied and there is a demand fordehumidification, the cooling blower-off delay is decreased from90 sec to 5 sec.5. Continuous Blower ModeWhen the R-to-G circuit is closed by the thermostat, the blowermotor BLWM will operate at continuous blower airflow.Continuous blower airflow selection is initially based on the CF(continuous fan) selection shown in Fig. 65. Factory default isshown in Fig. 65. Terminal EAC-1 is energized as long as theblower motor BLWM is energized.During a call for heat, the furnace control CPU will transition theblower motor BLWM to continuous blower airflow or themid-range airflow, whichever is lowest. The blower motor BLWMwill remain ON until the main burners ignite then shut OFF andremain OFF for the blower-ON delay (25 sec in heat), allowing thefurnace heat exchangers to heat up more quickly, then restarts at theend of the blower-ON delay period at heat airflow..The blower motor BLWM will revert to continuous-blower airflowafter the heating cycle is completed. In heat the furnace controlCPU will drop the blower motor BLWM to heat airflow during theselected blower-OFF delay period before transitioning tocontinuous-blower airflow.When the thermostat “calls for low-cooling”, the blower motorBLWM will switch to operate at low-cooling airflow. When thethermostat is satisfied, the blower motor BLWM will operate anadditional 90 sec at low-cooling airflow before transitioning back tocontinuous-blower airflow.When the thermostat “calls for high-cooling”, the blower motorBLWM will operate at high cooling airflow. When the thermostat issatisfied, the blower motor BLWM will operate an additional 90 secat high-cooling airflow before transitioning back tocontinuous-blower airflow. When the R-to-G circuit is opened, theblower motor BLWM will continue operating for an additional 5sec, if no other function requires blower motor BLWM operation.Continuous Blower Speed Selection from Thermostat To selectdifferent continuous-blower airflow from the room thermostat,momentarily turn off the FAN switch or push button on the roomthermostat for 1-3 sec after the blower motor BLWM is operating.The furnace control CPU will shift the continuous-blower airflowfrom the factory setting to the next highest CF selection airflow asshown in Fig. 65. Momentarily turning off the FAN switch again atthe thermostat will shift the continuous-blower airflow up one moreincrement. If you repeat this procedure enough you will eventuallyshift the continuous-blower airflow to the lowest CF selection asshown in Fig. 65. The selection can be changed as many times asdesired and is stored in the memory to be automatically usedfollowing a power interruption.NOTE: If the blower-off delay is set to the maximum, the adjustablecontinuous-fan feature is locked (i.e., fan speed cannot be changed fromits current setting).6. Heat pumpSee Fig. 42 and thermostat wiring for connections.When installed with a heat pump, the furnace control automaticallychanges the timing sequence to avoid long blower off times duringdemand defrost cycles. Whenever W/W1 is energized along withY1 or Y/Y2, the furnace control CPU will transition to or bring onthe blower motor BLWM at cooling airflow or the mid-rangeairflow, whichever is lowest. The blower motor BLWM will remainon until the main burners ignite then shut OFF and remain OFF for25 sec before coming back on at heating airflow. When the W/W1input signal disappears, the furnace control begins a normal inducerpost-purge period while changing the blower airflow. If Y/Y2 inputis still energized the furnace control CPU will transition the blowermotor BLWM airflow to cooling airflow. If Y/Y2 input signaldisappears and the Y1 input is still energized the furnace controlCPU will transition the blower motor BLWM to low-coolingairflow. If both the Y1 and Y/Y2 signals disappear at the same time,the blower motor BLWM will remain on at heat airflow for theselected blower-OFF delay period. At the end of the blower- OFFdelay, the blower motor BLWM will shut OFF unless G is stillenergized, in which case the blower motor BLWM will operate atcontinuous blower airflow.Component Self-TestRefer to “Component Self Test” in the Service and Maintenance sectionfor details.Wiring DiagramsRefer to Fig. 76 for wiring diagram.TroubleshootingRefer to the service label, see Fig. 70, wiring diagram, see Fig. 76, andthe Service Guide (Page 52) can be a useful tool in isolating furnaceoperation problems. The Guide will help to identify the problem orfailed component. After replacing any component, verify correctoperation sequence.