Bradford-White Corp MI30T*F service manual Resettable Thermal Switch Continuity Testing

TheBradfordWhite

DEFENDER

Safety System®

SERVICE PROCEDURE RG-VIII

Resettable Thermal Switch

Testing and Replacement

RESETTABLE THERMAL SWITCH CONTINUITY TESTING

Step 1. Remove outer jacket door.

Step 2. Disconnect wire leads from resettable thermal switch.

Step 3. Using a multimeter capable of measuring continuity (Ohms), place one probe of 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 over heating condition. The switch is designed to open at predetermined temperatures depending on model. 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 heater back in service.

PROBABLE CAUSE FOR RESETTABLE THERMAL SWITCH ACTIVATION

	PROBABLE CAUSE			CORRECTIVE ACTION
		1.	Verify adequate combustion air supply is
			available.
Insufficient combustion air		2.	Clear jacket slot openings of any dirt, dust,
			restrictions or other obstructions.
		3. inspect flame arrestor plate and clean with
			stiff brush and/or vacuum to remove scale
			deposits and debris.
1. Weak switch or switch		1. Replace resettable thermal switch
out of calibration.		2.	Verify switch color code and approximate
2. Incorrect switch.			temperature.
Flammable vapor incident		1. Replace water heater.

Resettable thermal switch

color code reference.

Approximate switch

Color Code activation temperature (open)

Blue	240°
Yellow	270°
Red	290°

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