# Gas water heater thermal limit keeps tripping



## KAdams4458 (Jan 29, 2006)

I never knew that I could actually hate an inanimate object, but it seems that I can. Someone help me figure this problem out before I tie a chain to this thing and rip it out of the house, then run over it several times with a large truck.

The problem is a Bradford White 50 Gallon propane-fired water heater that repeatedly trips the thermal limit switch. I've cleaned the burner several times, I've adjusted the flame perfectly, and I've made sure that the air intake path is clear. Sometimes, it will work perfectly for weeks on end without issue, and at other times, like the past few days, it will trip the thermal limit switch several times each day.

I'm gonna blow a gasket if I get one more surprise cold shower. :furious: Could the thermal limit switch just be malfunctioning?

Edited to add that the water heater is the only gas device in use in the entire house.


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## Gladerunner (Mar 9, 2010)

Is it a conventional flue or a power vent? possible that something is affecting draft? no big deal to replace limit switch just for giggles


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## Yoyizit (Jul 11, 2008)

Or look for a Tech. Service Bulletin addressing this problem. 
What temp. is it designed to trip at?


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## KAdams4458 (Jan 29, 2006)

just a guy said:


> Is it a conventional flue or a power vent? possible that something is affecting draft? no big deal to replace limit switch just for giggles


Conventional flue, but there's no way it's a draft issue. It's just too random for that. It's stayed lit all through heavy winds, but today it tripped and shut down five times, and there's not even a hint of a breeze.


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## KAdams4458 (Jan 29, 2006)

Yoyizit said:


> Or look for a Tech. Service Bulletin addressing this problem.
> What temp. is it designed to trip at?


The only bulletin I found for it had to do with a regulator recall, but this model wasn't affected. 

As for what temp it trips at... I have no idea. That information is missing from the manual. I could try hunting down the part number for the thermal limit switch and maybe find a spec that way.

All I can think to try is replacing the thermal limit switch. I'm guessing an HVAC supply place might carry something like that.


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## Yoyizit (Jul 11, 2008)

KAdams4458 said:


> All I can think to try is replacing the thermal limit switch. I'm guessing an HVAC supply place might carry something like that.


But keep the old part. . .


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## MACPLUMB (Jan 21, 2008)

kadams4458 said:


> the only bulletin i found for it had to do with a regulator recall, but this model wasn't affected.
> 
> As for what temp it trips at... I have no idea. That information is missing from the manual. I could try hunting down the part number for the thermal limit switch and maybe find a spec that way.
> 
> All i can think to try is replacing the thermal limit switch. I'm guessing an hvac supply place might carry something like that.


most likely you will find that this is a oem part and needs to

be ordered direct from b/w,

but they "may" not sell to you as they deal only with licensed

contractors !


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## KAdams4458 (Jan 29, 2006)

Wait... I found the specification for the thermal overload switch in the service manual. How I managed to miss it several times is beyond me.

The switches are colour coded, and the red switch in this water heater is rated to open at approximately 290 degrees. (I'm looking at the paint daub, not the colour of the plastic button, which are all red.) The problem is, the service manual says that there should be a yellow switch installed with a 270 degree rating. Uhhh. What?

I'm starting to get the same feeling I got when the previous owner said the roof had never leaked, but I could see daylight through it in places. It's not a good feeling.


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## Yoyizit (Jul 11, 2008)

KAdams4458 said:


> The switches are colour coded, and the red switch in this water heater is rated to open at approximately 290 degrees.


It'd be tricky but you can produce 290F for testing it.


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## KAdams4458 (Jan 29, 2006)

Yoyizit said:


> It'd be tricky but you can produce 290F for testing it.



I was thinking of hooking up my test set with the thermocouple probe near the switch on the heater, setting the meter to record the highest temp, and waiting for it to trip again. Now that you have mentioned producing heat and testing it, I'm thinking I could just pull the switch, and put it in my powder coating oven, which can control temperature within one degree.

I can set the oven temp to about 250 or so, and just bump it up five degrees at a time until it opens.

Of course, I'm only guessing that the entire switch will handle that kind of temperature. It could be a good way to melt the side of the switch that isn't intended to be exposed to heat, for all I know.


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## Yoyizit (Jul 11, 2008)

KAdams4458 said:


> Sometimes, it will work perfectly for weeks on end without issue, and at other times, like the past few days, it will trip the thermal limit switch several times each day.


I don't see what could cause this pattern.


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## KAdams4458 (Jan 29, 2006)

Yoyizit said:


> I don't see what could cause this pattern.


That makes at least two of us. I've been putting up with it for a year and a half now, and am really at the point where I'm ready to replace it, even though it is only four years old. 

Abort, Retry, Fail? :laughing:


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## Sparky8370 (Jan 7, 2009)

I had a wall mounted boiler in a condo. Whoever designed the place put the boiler right in the laundry room. It would take lint in and clog up the coil. This would reduce the draft, compounding the problem by making the gas burn incomplete and further clog the coil. This would cause the flame to roll out and around and activate that switch. PITA


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## MACPLUMB (Jan 21, 2008)

GET TO THE PART WHERE YOU TALKED TO BRADFORD WHITE 

TECH. SUPPORT ? :whistling2:

THAT IS WHAT THEY ARE THERE FOR ! !

YOU MAY ONLY BE TREATING A SYMPTOM OF THE PROBLEM NOT THE REAL

CAUSE OF IT ! ! :thumbsup:


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## plumber Jim (Mar 30, 2008)

You may want to make sore you have no flammable vapors causing it to trip. I have a vet that had that same problem and his plumber bypassed the switch and he ended up with a fire. turned out that he had a propane leak that seeped in through his floor and would ignite and trip the switch ( as it should) so make sure you don't have a heater doing just as designed and a much bigger problem.


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