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All installations and services must be performed by qualified service personnel.
Operating Modes for UT board (PSC)
Standby Mode
All outputs are off and the control is waiting for a thermostat demand. The thermostat inputs, and
limit switch are continuously monitored. The control initiates action when a thermostat call is
received or limit switch opens.
Fan Mode
A call for fan ("G") is received from the thermostat. If no other mode is calling for blower
operation, the control will operate the fan relay (K4) and power the "Low" blower speed
terminal. The fan mode will be operated as long as the "G" input is calling and neither the Heat
mode nor the Cool mode is calling for blower operation. When the Heat and Cool modes call for
blower operation, their respective outputs will take precedence after their respective turn-on time
delays have expired.
Cooling Mode
A call for cool ("Y") is received from the thermostat. If the heat mode is not active or the anti-
short cycle delay is not in effect, the control will energize the "CC" terminal and after a 10
second power demand conservation delay energizes the "COOL" speed blower terminal.
When the call for cool is satisfied, the "CC" terminal is de-energized and the cooling off delay of
45 seconds is started. Forty-five seconds later the "COOL" speed blower terminal is de-
energized and the control reverts to Standby Mode.
Dehumidification Operation
If a call for dehumidification is received while the Cool Mode is active, blower speeds will be
reduced. The "COOL" blower speed terminal will be de-energized and "Low" blower speed will
be energized.
Anti-Short Cycle Operation
To prevent compressor short cycling, a call for cooling will be ignored for four minutes after the
termination of any cooling call. The anti-short cycle delay is also in effect at power-up.
EAC (electronic air cleaner)
If a call for fan ("G"), cool ("Y") or heat ("W") is received from the thermostat, the "EAC"
terminal is energized whenever the blower is energized to power an electronic air cleaner.
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