Mastertemp 400 Thermal Regulator

[jimbethesda]

Hi all. My heater has been cycling on/off when the water reaches about 85 degrees. I read a few threads on here on how to troubleshoot. I originally thought it was the high limit switch, but I replaced it and it was still shutting off.

I then removed the thermal regulator (see pic) and now it’s working fine. I ordered a new one, but it won’t come in for about a week or so.

So...my question is...can I run the heater without the regulator just until the new one comes in? I read somewhere that it will be less efficient (not ideal, but ok short term), any other concerns? Will it cause any other damage?

Thanks as always.

 

[jimbethesda]

Just bumping this. Thanks

 

[mknauss]

Mine went bad last year. I did not run the heater without the new one.
From the manual "A thermal regulator and an internal bypass regulate the water flow
through the heat exchanger to maintain the correct outlet temperature."

I am not sure of the harm of running the heater with out the thermal regulator. It could result in lower temperature in the heat exchanger, but not sure what that can harm. Maybe lower combustion chamber temperature?

@JamesW would be best to consult on this.

 

[JamesW]

I can't recommend running without the correct parts.

Mostly, it prevents condensation from forming on the heat exchanger.

If you don't have really cold water where the pipes are sweating, then you probably won't have condensation on the heat exchanger.

If the heater is going to be running, the thermal regulator would be open anyway.

So, I don't think that there would be a problem.

In any case, I would not feel comfortable saying that it's ok to run without the thermal regulator.

There might be some reason that I am not aware of that might make a difference.

 

[jimbethesda]

I can't recommend running without the correct parts.

Mostly, it prevents condensation from forming on the heat exchanger.

If you don't have really cold water where the pipes are sweating, then you probably won't have condensation on the heat exchanger.

If the heater is going to be running, the thermal regulator would be open anyway.

So, I don't think that there would be a problem.

In any case, I would not feel comfortable saying that it's ok to run without the thermal regulator.

There might be some reason that I am not aware of that might make a difference.

Thanks. I found a different place to get the part, now it’s arriving on Wednesday. I ran it a little bit with it removed yesterday (daughter had a friend over and wanted to go into the hot tub). I don’t think I’ll use it again until the part comes in.