ICP 9MAC/E series Troubleshooting Manual

Contents

ICP 9MAC/E series Troubleshooting Manual Manual pdf 6 page image

- 6 -3. Cooling Off-Delay - When the “call for cooling” is satisfiedand there is a demand for dehumidification, the cooling blower-off delay is decreased from 90 seconds to 5 seconds.SUPER-DEHUMIDIFY MODESuper-Dehumidify mode can only be entered if the furnace control isin the Dehumidification mode and there is a demand fordehumidification. The cooling operation described in the CoolingMode section above also applies to Super Dehumidify Mode. Theexceptions are listed below:1. Low Cooling – When the R to Y1 circuit is closed, R to Gcircuit is open, and there is a demand for dehumidification, thefurnace blower motor BLWM will drop the blower airflow to65% of low-cooling airflow for a maximum of 10 minutes eachcooling cycle or until the R to G circuit closes or the demand fordehumidification is satisfied. Low-cooling airflow is the trueon-board CF selection as shown in Table 1.2. High Cooling – When the R to Y/Y2 circuit is closed, R to Gcircuit is open, and there is a demand for dehumidification, thefurnace blower motor BLWM will drop the blower airflow to65% of high-cooling airflow for a maximum of 10 minutes eachcooling cycle or until the R to G circuit closes or the demand fordehumidification is satisfied. High-cooling airflow is based onthe A/C selection shown in Table 1.3. Cooling Off-Delay – When the “call for cooling” is satisfiedand there is a demand for dehumidification, the cooling blower-off delay is decreased from 90 seconds to 5 seconds.CONTINUOUS BLOWER MODEWhen the R to G circuit is closed by the thermostat, the blower motorBLWM will operate at continuous blower airflow. Continuousblower airflow selection is initially based on the CF selection shownin Table 1. Factory default is shown in Table 1. Terminal EAC-1 isenergized as long as the blower motor BLWM is energized.During a call for heat, the furnace control CPU will transition theblower motor BLWM to continuous blower airflow, minimum-heatairflow, or the midrange airflow, whichever is lowest. The blowermotor BLWM will remain ON until the main burners ignite then shutOFF and remain OFF for the blower-ON delay (45 seconds inintermediate-heat, and 25 seconds in maximum-heat), allowing thefurnace heat exchangers to heat up more quickly, then restarts at theend of the blower-ON delay period at modulating or maximum-heatairflow respectively.The blower motor BLWM will revert to continuous-blower airflowafter the heating cycle is completed. When the thermostat satisfies,the furnace control CPU will drop the blower motor BLWM tominimum-heat airflow during the selected blower-OFF delay periodbefore transitioning to continuous-blower airflow.When the thermostat "calls for low-cooling", the blower motorBLWM will switch to low-cooling airflow. When the thermostat issatisfied, the blower motor BLWM will operate an additional 90seconds at low-cooling airflow before transitioning back tocontinuous-blower airflow.When the thermostat "calls for high-cooling", the blower motorBLWM will switch to high cooling airflow. When the thermostat issatisfied, the blower motor BLWM will operate an additional 90seconds at high-cooling airflow before transitioning back tocontinuous-blower airflow.When the R to G circuit is opened, the blower motor BLWM willcontinue operating for an additional 5 seconds, if no other functionrequires blower motor BLWM operation.HEAT PUMP DEFROSTWhen 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 with Y1or Y/Y2, the furnace control CPU will transition to or bring on theblower motor BLWM at cooling airflow, minimum-heat airflow, orthe midrange airflow, whichever is lowest. The blower motorBLWM will remain on until the main burners ignite then shut OFFand remain OFF for 25 seconds before coming back on atmodulating heat airflow. When the W/W1 input signal disappears,the furnace control begins a normal inducer post-purge period whilechanging the blower airflow. If Y/Y2 input is still energized thefurnace control CPU will transition the blower motor BLWM airflowto cooling airflow. If Y/Y2 input signal disappears and the Y1 inputis still energized the furnace control CPU will transition the blowermotor BLWM to low-cooling airflow. If both the Y1 and Y/Y2signals disappear at the same time, the blower motor BLWM willremain on at minimum-heat airflow for the selected blower-OFFdelay period. At the end of the blower-OFF delay, the blower motorBLWM will shut OFF unless G is still energized, in which case theblower motor BLWM will operate at continuous blower airflow.COMPONENT TESTThe furnace features a component test system to help diagnose asystem problem in the case of a component failure. To initiate thecomponent test procedure, ensure that there are no thermostat inputsto the control and all time delays have expired. Turn on setup switchSW1-6. (See Appendix A)Note: The component test feature will not operate if the control isreceiving any thermostat signals or until all time delays have expired.The component test sequence is as follows:1. The furnace control CPU turns the inducer motor IDM ON atmedium speed and keeps it ON through step 4.2. The furnace control CPU will test communication with themodulating gas valve GV.3. After waiting 15 seconds the furnace control CPU turns the hotsurface igniter ON for 15 seconds, then OFF.4. The furnace control CPU then turns the blower motor BLWMon at midrange airflow for 15 seconds, then OFF.5. After shutting the blower motor OFF the furnace control CPUshuts the inducer motor IDM OFF.Note: The EAC terminals are energized when the blower isoperating.After the component test is completed, 1 or more status codes(Heartbeat, 2 + 5, 3 + 5, 4 + 1, or 4 + 2) will flash. See Service Labelon control door or Service/Status Code Instructions for explanationof status codes.Note: To repeat component test, turn setup switch SW1-6 to OFFand then back ON.440 08 4001 00