All installations and services must be performed by qualified service personnel.
15
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.
2 Stage Control
Inputs: LIMIT - 120vac power from the High Limit Switch used to power the burner.
W1- Switched 24vac indicating a Heat call from the thermostat. (Low fire)
W2- Switched 24vac indicating a Heat call from the thermostat. (High fire)
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.
NOTE: 2-Stage T-stat
W1 – Low Fire
W2 – High Fire
Connect 2-Stage T-stat to both W1 and W2.
Single Stage T-stat
W2
Connect single stage T-stat to W2 only.
BLOWER Speeds:
HEAT - The Heating Blower speed selected by positions 1, 2 & 3 of SW1 (CFM tables on page 4)
COOL - The Cooling Blower speed selected by positions 4, 5 & 6 of SW1 (CFM tables on page 4)
LOW - The LOW Blower speed selected by positions 4, 5 & 6 of SW1 (CFM tables on page 4)
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.
Summary of Contents for OH16-125
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