Thermo Products ome-72d36 service manual C. Operating Modes

All installations and services must be performed by qualified service personnel.

EAC (electronic air cleaner)

The control provides a 120 VAC output for an electronic air cleaner. This output is energized whenever the fan motor is energized (either low, heat or cool speed). Connection is made via male quick connect terminal labeled “EAC”.

Humidifier

The control provides a 120 VAC output for a humidifier. Connections are made to a male quick connect terminal labeled “FAN”. The control does not switch this output, it provides a pass-through connection from P1-7 from the switched primary voltage of the Burner Module.

Status LED

A red LED is provided to indicate any thermostat input has been recognized by the microprocessor on the control. See Diagnostic Features for a function description of operation.

Thermostat Input LEDs

Four green LEDs are placed beneath their respective thermostat connections (W, Y, G and DEHUM) and operate whenever a call is present. See Diagnostic Features for a function description of operation.

C. Operating Modes

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 PSC “COOL” blower speed terminal (1158-100 model only) 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.

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