Controls
Operating sequence
All units require the addition of a thermostat accessory package to complete the control circuit. The sequence of operation may vary depending on which package is selected.
Room-mounted thermostat — The unit uses an electronic thermostat mounted in the conditioned space.
Fan circulation — When the thermostat selector switch is set to the FAN position, the evaporator-fan motor will operate to provide air circulation.
Cooling — The evaporator will operate continuously or when the compressor runs, depending on the setting of the thermostat fan selector switch. When the thermostat closes (on a call for cooling), the control relay condenser-fan con- tactor and compressor contactor(s) close. The control relay will start the indoor fan if it is not already running. The condenser fan contactor will start the condenser air fan and the compressor contactors will immediately start the compressor(s).
A second stage on 50XCA12 to 24 units will close if additional cooling demand is required, and will start the second-stage compressor. When the thermostat is satisfied, the second-stage compressor will stop first, and then the first-stage compressors will stop when cooling demand is satisfied. The condenser will also stop as soon as both cool- ing stages are satisfied.
A5-minute timer, TDR (time-delay relay), will prevent the compressor(s) from restarting for 5 minutes after any compressor has stopped.
All units — The control circuit incorporates a current sensing lockout relay (Cycle-LOC™ device) that locks off the compressor(s) when any safety device is activated (low or high pressure switches, or compressor internal over- load). If any compressor safety device opens, the compres- sor will stop. High and low-pressure switches and compressor motor overload protectors will reset automati- cally when the condition which caused the device to trip has dropped below the reset condition. To reset the Cycle- LOC control device, manually turn the control power OFF, then back ON.
