Another Pentair Master Temp 400 turning on and off again with a twist ?

[724Bravo]

Hello All,
I have a 7yr old Pentair Master Temp 400 that is turning on and off right when it heats up to 90 deg. with a "service heater" light coming on at shutdown.
Here's the twist in the equation while in the Spa Heating mode as the temperature is increasing before hitting the 90deg. mark, when I turn on the jets the heater shuts off?
Turn the jets off and the heater will the n start back up.
I have replaced All the sensors and the thermal regulator except for the pressure switch, Heat Exhaust temp was 309, filter pressure is 19.
Yesterday while in the heating mode I unplugged the PS lead and the heater shut off I also jumped the PS leads while heating up and the unit shut off at the faithful 90deg. mark.
For some reason I think it might be the PS because when the jets come on that increases the water pressure going through the heater right ? and the heater shuts off !! Is there a correlation here IDK
There are no visible corrosion issues or leaks, the unit looks great.
What else could it be and I missing something ?
Is my heater core shot ?


Thanks in advance.

Bill

 

[Poolbreh]

Can you post pic of the equipment and a video? Any led lights on the back of the board when it shuts off? They may appear briefly

 

[724Bravo]

There is only the service heater light that comes on, on the heater unit after it shuts off.

 

[Poolbreh]

Your jet pump looks like it’s on its own loop. Unless it’s sharing the same suction as your spa intake. Does your psi drop when your in spa mode and you turn the jet pump on? What light on the back of the board comes on when the heater shuts off?(without jet pump)

 

[724Bravo]

Same as when the jets are on the service heater light.
Here are a few more photo's also the pipe's do shake a bit when the heater comes on.

 

[Poolbreh]

The led lights are on the back of the board of the heater you have to open the front panel and look underneath. PS, AGS, HLS and so on it may only come on briefly when the heater shuts off. Is there a psi drop when the jet pump is turned on while in spa mode?

 

[724Bravo]

I didn't see any pressure drop when the booster pump turned on.
When the Heater turns off the service heater light turns on as well as a red led HLS.
Here's a screen shot of the HLS light.

 

[Poolbreh]

It sounds like you may have gotten a dud thermal regulator you can pull it and put the cap back on fire the heater and hold the regulator over the vent to see if it opens. Or you can test it in a cup of hot water and see if it opens. I would test that first if it proves to be faulty, after it’s fixed we can address jet pump issue. Don’t run the heater for long without the thermal regulator.

 

[Poolbreh]

 

[724Bravo]

Thermal Reg works as it should.

So what is the Jet Pump issue you speak of ?

 

[Poolbreh]

What rpms are you running the heater?
Since thermal regulator checks out I would check the internal bypass.

The jet pump is on its own loop and shouldn’t cause any issues with the heater unless it shared a intake line under ground which would cause a drop in pressure. Unless you are referring to “jets” being a circuit feature. It’s probably best to address the heater first and it shutting off at 90 and see if it fixes both issues. If not after heater is fixed we can figure out “jet” issue. The pressure switch is just a spring loaded piston that hits a micro switch.

 

[724Bravo]

Pool/Spa Heater-2500rpm's
Jets-3000rpm's

With the T-Reg removed and with the Spa turned on I ran it for a few minutes and then turned on the Jet pump, after a few minutes the heater should have turned off, but it did indeed stay on.
Also, it was a PITA getting the T-Reg. out of the housing it was hung up on something and according to the Video above there shouldn't be anything near the T-Reg. device it should slide in and out without issue.
I re-installed the T-Reg. and it again would turn off and on with the Jet pump turned on.
As you mentioned I suspect that the Internal Bypass vale is the issue.
I will order a "o" ring kit along with a IBV and open her up.
I'll report back next week when I open up the housing.

Thank you so much for your help.

Bill