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HOM Troubleshooting
TROUBLE-SHOOTING COMBUSTION AIR DAMPER - SERIES "HOM"
Part ONE refers to FUSE TYPE
Part TWO refers to TEST/RUN SWITCH TYPE
PART ONE, FUSE TYPE:
General: Note: Damper uses power to close when appliance is not firing and does not use power when appliance is firing. This prevents overloading the appliance transformer.
Two wires from the damper motor are connected to the appliance transformer and two wires from the damper relay are connected in series with one stat wire.
NOTE: Fuse is part of signal circuit only and not part of motor circuit
Condition: Damper does not close after appliance completes its firing cycle.
Cause: Indicates a 1) faulty relay or 2) no power supply or 3) faulty motor.
Procedure: Remove control body cover and use a jumper between terminals 3 & 4. If damper closes faulty relay. If no response, check power supply to terminals 3 & 5 or connect power supply to terminals 4 & 5. No response indicates a faulty motor.
Condition: Damper does not open when thermostat asks for heat.
Cause: This indicates 1) signal is not getting through from the thermostat via the fuse to the relay or 2) damper is stuck closed or 3) mechanical friction in motor gears.
Procedure: Remove control body cover and with jumper, join terminals 1 & 5. If damper opens, a faulty stat is suspected. Turn Test/Run switch to the "down" position and if appliance does not fire, a faulty stat is confirmed. 2) If damper has not be activated for a period of time, (e.g. summer months) the damper might stick closed due to residue. Clean damper blade with soap and water. 3) Motor gears wear with age causing increased friction which prevents the damper from opening freely. Replace motor.
Condition: Damper opens on stat signal but appliance does not fire.
Cause: This indicates: 1) faulty appliance, 2) improper linkage to end switch or 3) a faulty end switch.
Procedure: Remove control body cover and use a jumper between terminals 1 & 2. No response indicates a faulty heating system. If appliance responds, 2) check end-switch linkage by listening for a "click" as the damper blade opens to approximately 30 degrees. To correct, bend end switch lever arm to suit. 3) If linkage is correct, a faulty end switch is suspected.
PART TWO, TEST/RUN SWITCH TYPE:
General: NOTE: Damper uses power to close when appliance is not firing and does not use power when appliance is firing. This prevents overloading the appliance transformer.
Two wires from the damper motor are connected to the appliance transformer and two wires from the damper relay are connected in series with one stat wire.
Condition: Damper does not close after appliance completes its firing cycle.
Cause: Indicates 1) Test/Run switch is not in the "up" position or 2) a faulty relay or 3) no power supply or 4) faulty motor.
Procedure: 1) Check Test/Run switch to be in the "up" position. If no response, 2) Remove control body cover and use a jumper between terminals 3 & 4. If damper closes faulty relay. If no response, 3) check power supply to terminals 3 & 5 or 4) connect power supply to terminals 4 & 5. No response indicates a faulty motor.
Condition: Damper does not open when thermostat asks for heat.
Cause: This indicates 1) signal is not getting through from the thermostat to the relay or 2) damper is stuck closed or 3) mechanical friction in motor gears.
Procedure: 1) Some installations have an auxiliary in-line fuse between stat wire and damper black wire #1. Check for burn-out. If this is not the cause, remove control body cover and with jumper, join terminals 1 & 5. If damper opens, a faulty stat is suspected. Turn Test/Run switch to the "down" position and if appliance does not fire, a faulty stat is confirmed. 2) If damper has not been activated for a period of time, (e.g. summer months) the damper might stick closed due to residue. Clean damper blade with soap and water. 3) Motor gears wear with age causing increased friction which prevents the damper from opening freely. Replace motor.
Condition: Damper opens on stat signal but appliance does not fire.
Cause: This indicates: 1) faulty appliance, 2) improper linkage to end switch or 3) a faulty end switch.
Procedure: 1) The combustion air Damper is interlocked with the heating appliance control system. This feature is by-passed by using the TEST/RUN switch in the down position. Thus the stat wire is reconnected to "W" (TH) on the appliance. If heating appliance does not fire with this switch in the down position, a faulty heating system is suspected. If appliance responds, 2) Check end switch linkage by listening for a "click" as the damper blade opens to approximately 30 degrees. To correct, bend switch lever-arm to suit. 3) If linkage is correct, a faulty end switch is suspected.
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