All installations and services must be performed by qualified service personnel.; Sequence of Operation Glossary ; ECM – PSC Replacement - Page 14

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

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Sequence of Operation Glossary 

Inputs:  LIMIT - 120vac power from the High Limit Switch used to power the burner. 
 

W- Switched 24vac indicating a Heat call from the thermostat. 

Y - Switched 24vac indicating a Cool call from the thermostat. 

G - Switched 24vac indicating a call for blower operation from the thermostat. 

DEHUM - Switched 24vac indicating a call for Dehumidification from a de-humidistat. 

 
BLOWER Speeds: 

HEAT - The Heating Blower speed selected by positions 1, 2 & 3 of SW1 (CFM tables on page 6) 

COOL - The Cooling Blower speed selected by positions 4, 5 & 6 of SW1  (CFM tables on page 6) 

LOW - The LOW Blower speed selected by positions 4, 5 & 6 of SW1  (CFM tables on page 6) 

 
ECM – PSC Replacement 

In an emergency situation, a defective ECM motor can be replace with a PSC motor to provide temporary 
circulating air flow for heating or cooling.  This is done by replacing the ECM motor in the motor mounting bracket 
with a PSC motor of similar Horsepower.  Wire the common lead (typically white) of the replacement PSC motor to 
the neutral (common) terminal on the fan control board (N - 1 through 7).  Connect the high-speed replacement PSC 
motor lead (typically black) to the EAC terminal on the fan control board.  The EAC contact is energized with 
115VAC any time the control board is calling for fan operation whether in heating or cooling mode.  This 
replacement should be only used in emergency situations and only until a replacement ECM motor can be obtained 
and reinstalled.