A.O. Smith 120 trough 500

BTR TANK TYPE HEATERS

SERVICE HANDBOOK

A.O. Smith Water Products Service Handbook

STEP 4 INSPECT THE DAMPER

STEP 4. INSPECT THE DAMPER. Lower the thermostat setting so the unit will not be

calling for heat, then inspect the damper.

IF THEN

If the damper is open: • Go to step 5.

If the damper is closed: • Go to step 7.

Note: If the water temperature in the tank is below 120 degrees F, temporarilydisconnect the

jumper wire between the high limit and thermostat to simulate a satisfied thermostat.

STEP 5 CHECK THE PC BOARD

STEP 5. CHECK THE PC BOARD. Test for 24 VAC between the black PC board wire

connection and ground.

IF THEN

24 VAC is not present: • Check the black wire connections

between PC Board and high limit.

24 VAC is present: • Go to step 6.