Resettable Thermal Switch Inspection & Replacement - Bradford White UPV Series Service Manual

UPV Service Procedure XV – Resettable Thermal Switch Testing and
Replacement
Resettable Thermal Switch Continuity Testing
Step 1. Remove outer jacket door.
Step 2. Disconnect black wire leads from the resettable
thermal switch.
Step 3. Using a multimeter capable of measuring continuity
(Ohms), place one probe of the meter on one of the
brass connection tabs of the resettable thermal
switch, and the remaining probe on the other
connection tab.
Step 4. If continuity is indicated, the switch is closed, allowing
millivolt current to pass.
Step 5. If continuity is not indicated, the switch is open,
possibly due to an overheating condition. The switch
is designed to open at predetermined temperatures.
An open switch can be reset by depressing the red
colored button located at the center of the switch.
The overheating condition must be determined prior
to putting the water heater back into service.
Probable Cause for Resettable Thermal Switch
Probable Cause
Insufficient
combustion air
1. Weak switch or
switch is out of
calibration.
2. Incorrect switch.
Flammable vapor
incident
Activation
Corrective Action
1. Verify adequate
combustion air supply is
available.
2. Clear jacket slot openings
of any dirt, dust,
restrictions or other
obstructions.
3. Inspect flame arrestor
plate and clean with a stiff
brush, compressed air
and/or vacuum to remove
scale deposits and
debris.
1. Replace resettable
thermal switch.
2. Verify switch color code
and approximate
temperature.
Replace water heater
Resettable Thermal Switch Color Code
Color code
Blue
Yellow
Red
37
Reference
Approximate
switch activation
temperature (open)
240°
270°
290°
37