Arkansas HVACR NewsMagazine March 2022

HVACR NewsMagazine March 2022

Tech News

Blower on G

If the float switch breaks Y instead, then power can't access the contactor coil, meaning that it can't pull in the contactor. Without pulling in the contactor, an electrical path cannot be made to the compressor and condenser fan. As a result, those critical components fan can't run. The Y circuit also goes in and out of the high-pressure and low-pressure switches before it even reaches the contactor coil. As with the float switch, if either of those pressure switches open, Y would break, and the system would not run. The white wire that goes to the W terminal on the thermostat also goes to the W terminal on the defrost board from the terminal block, which is a junction point within the air handler. When the backup heat kicks in, a signal also travels to the defrost board, which allows the defrost board to back feed and bring on heat strips, too. In other words, both the thermostat AND the defrost board have the ability to bring on the backup heat. Auxiliary heat on W

The G terminal supplies constant 24v power to the blower motor. If the fan setting is set to ON instead of AUTO, there will be 24 volts of electricity going to the blower motor at all times. Common feeds directly from the secondary of the transformer to the thermostat wire and the defrost board. We need common because it's the path back to the transformer; without common, we wouldn't have a complete circuit, and the heat pump wouldn't work. The orange wire goes from the thermostat to the terminal block near the transformer and then to the condensing unit, where it can energize the reversing valve solenoid. When we use the ACC+ terminal for dehumidification, the wire runs right from the thermostat to the DH terminal on the terminal block. The blower can't come up to full speed unless the DH terminal is energized. Common on C Reversing valve on O or B ACC+ for dehumidification