A.O. Smith 120 trough 500 User Manual

Page 27

BTR TANK TYPE HEATERS

SERVICE HANDBOOK

A.O. Smith Water Products

Service Handbook

Training Department

STEP 10

TEST DAMPER OUTPUT

STEP 10. TEST DAMPER OUTPUT.

On a call for heat, the damper relays receives

power through the yellow wire and power to the motor is interrupted.

Then, the motor

clutch is disengaged and the damper opens. The damper proves it is open via an end
switch before power flows through the red wire from the PC board.

Place the red test probe on the solder joint of the red wire connection to the damper PC
board.

THEN

The meter does not read 24 VAC and the
end switch is closed:

• Replace the PC board

The meter reads 24 VAC

• Go to step 11.

Note: The spring rotates the damper blade assembly to the open position. This closes an end
switch.