A.O. Smith 120 trough 500 User Manual

Page 22

BTR TANK TYPE HEATERS

SERVICE HANDBOOK

A.O. Smith Water Products

Service Handbook

Training Department

STEP 3

TEST HIGH LIMIT RIGHT TERMINAL

STEP 3.

TO TEST HIGH LIMIT RIGHT TERMINAL. Ensure that the jumper wire

between the high limit and thermostat is connected, and the damper motor power line is
connected. Test for 24 VAC between the high limit right terminal and ground.
IF

THEN

The meter does not read 24 VAC:

• Push the reset button and redo the test (storage

water temperature below 185 degrees).

The meter reads 24 VAC:

• Go to step 4.

After Push in Reset - 24 VAC is now present

Reasons For Resetting

Condition

Cause

Solution

High limit open

Never set on initial
installation

Push high limit button

Excessive water temperature

Faulty thermostat

Replace dual control

Heater shut down before
reaching thermostat setting

Faulty high limit

Replace dual control

Note: The right terminal of the high limit has a jumper wire connected to the left terminal of the
thermostat. There is also a black wire connecting to the damper motor assembly. This black wire
supplies power to the motor to close the damper during periods of standby.