Pentair Master Temp 400 Thermal Regulator Question- before I screw it up...

[wwtennant]

Team TFP,

So, I read a number of threads about the Master Temp 400 cycling above a certain temperature- which is the problem that I am having. So, I attempted to remove the Thermal Regulator and see if it looked bad or reach in and see if the bypass was bad.

First error- apparently, i do not know where it is... at least on the first try. So... I ended up disconnecting some wires from the two screen in caps on the left side of the heating manifold. Then, i removed the bottom plug (HLS switch maybe??). Well, water started streaming out so i quickly put it back in.

Second issue- now knowing where the Thermal Regulator actually is, I began to take it out. But then I heard water about to start flowing out. My pump is clearly off for all of this but my hot tub/spa is raised and thus any outlet lower than it (like all the pool equipment) will let water flow continuously until the spa empties.

Two questions:
1) Now that I took out the lower plug and simply screwed it back in... will it now leak unless I seal it??
2) If I pull the thermal regulator, will water come shooting out due to the pressure caused by the raised spa? If so, how do I stop that from happening?

Please advise as before I make this worse....

As always... thank you TFP!!

Best,

Warren

 

[JamesW]

Put the system in pool mode to isolate the heater from the spa. Then, turn off power so that a timer can't turn the pump on while you're working.

Then, remove the heater drain plug. After the heater drains, you can reseal the first part that you removed and you can access the thermal regulator.

Once you replace the thermal regulator, reinstall the drain plug and restart the system.

 

[wwtennant]

Thanks for the reply. A bit naive when it comes to the valves on my system so not sure what it means to be in "pool mode". The heater is used to heat both the pool and the spa if that makes a difference. Otherwise, I think you are telling me to cut off the spa entirely so that the gravity weight of the water doesnt run the water into the heater continuously.
1) Is that right??
2) When you say that I can "reseal" the HLS that I pulled out. Do you simply mean wait for everything to dry and reseat it? Or do I need to apply some sealant or teflon tape??

Thanks!!

 

[JamesW]

As long as the spa suction valve is closed, you should be ok.

The spa return should have a check valve that prevents the backflow of water.

Remove the drain plug and see if it stops draining in about 1 minute.

If the water stops in less than a minute, you're good.

Then, reseal the high limit with teflon tape or thread sealant. Then, you can remove and replace the thermal regulator.

After you replace the thermal regulator, reinstall the drain plug and restart the system.

 

[wwtennant]

Sorry to come back yet again but i have created a new issue. After removing the HLS switch and the thermal regulator and then replacing them, I now have air bubbles coming out of my jets in the elevated spa (but not in the pool). Which of the two openings is likely not sealed properly and allowing in air?? I would think they would leak instead of allow air in... thoughts?

Thank you!!

 

[JamesW]

Spa jets are often venturi type where they pull in air. So, that might be normal.

The ozonator makes bubbles, is that a possibility?

The SWG makes tiny hydrogen bubbles, that could be the issue.

Anything on the pressure side would leak water and typically not pull in air.

Air getting in the system is normally a suction side leak. Check the pump lid to see if there is air getting in the pump.

You probably got air in the filter. If that's what happened, it should clear after about 10 minutes.