38AU
OPERATING SEQUENCE
Base Unit Controls
Indoor (Supply) Fan —
The indoor fan contactor (IFC) is remotely located at the fan coil or fan section. If the thermostat fan operation is selected as Continuous, the IFC is energized and the indoor (supply) fan motor runs continuously. If the thermostat fan operation is selected as Automatic, the IFC will be energized on a call for Cooling; indoor (supply) fan motor runs. When thermostat call for Cooling is satisfied, the IFC is
Cooling, Unit Without Economizer —
38AUZ (Single Circuit)
On a thermostat call for Cooling, IFC will be energized and indoor (supply) fan motor runs. Thermostat output Y1 is energized; terminal Y1 at 38AUZ unit receives
On a thermostat calling for Stage 2 Cooling, thermostat output Y2 is energized; terminal Y2 at 38AUZ unit receives
As space cooling load is satisfied, thermostat outputs Y2 and Y1 are
38AUD (Two Circuit)
On a thermostat call for Cooling, IFC will be energized and indoor (supply) fan motor runs. Thermostat output Y1 is energized; terminal Y1 at 38AUD unit receives
On a thermostat calling for Stage 2 Cooling, thermostat output Y2 is energized; terminal Y2 at 38AUD unit receives
As space cooling load is satisfied, thermostat outputs Y2 and Y1 are
All Units
If either the Low Pressure Switch or High Pressure Switch opens while thermostat output Y1 or Y2 remain energized, the compressor contactor is
Complete system shutdown may be caused by loss of main power, open compressor internal overload, open
Cooling, Unit With Economizer —
Refer to fan coil unit installation instructions and economizer accessory installation instructions for operating sequences when system is equipped with accessory economizer.
Heating —
Refer to fan coil unit installation instructions and accessory heating device installation instructions for operating sequences in heating mode.
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