Thermo Pride OMD-70 - Manual (Page 28)

All installations and services must be performed by qualified service personnel.
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.
Heat Mode
When a call for heat (“W”) is received from the thermostat, if the “Cool” mode is not already active, the
“T-T” terminal is energized and the blower on delay is started. The on-off pattern of DIP switch SW2
(positions 1 and 2) select one of four blower on delay values (see Table 11). When the delay time has
elapsed, the “HEAT” blower speed is energized. The control remains in steady heat mode until the
thermostat is satisfied. When the call for heat signal is removed, the “T-T” terminal is de-energized and the
blower off delay is started. The on-off pattern of DIP switch SW2 (positions 3 and 4) select one of four
blower off delay values (see Table 11). When the delay time has elapsed, the “HEAT” blower speed
terminal is de-energized.
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