MT 400 - Service Heater - No code

[dcruff]

My heater shuts off every once in a while (recently daily) with a Service Heater light. I turn the heater off and back on and it then appears fine.
When I checked the back of the circuit board, none of the indicator lights were on, except for a red LED on the bottom right next to R15. There is no code associated with that light, so I'm assuming that it just comes on when the Service Heater indicator comes on the panel.
I don't want to just start replacing things but I don't know what else to do.

 

[ajw22]

Welcome to TFP.

Check the thermal regulator.

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

What pump and filter do you have?

What is your filter PSI?

When was the last time you cleaned your filter?

 

[dcruff]

Welcome to TFP.

Check the thermal regulator.

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

What pump and filter do you have?

What is your filter PSI?

When was the last time you cleaned your filter?

Thanks for the reply. I'll go ahead and check out the Thermal Regulator. Since there is no specific code or light on the circuit board associated with the thermal regulator, would it's failure set the Service Heater indicator?
Pentair Intelliflo VSF - I believe that it's 3HP (HHP:1.88 THP:3.95 WEF:6.9)
Pentair Clean & Clear Plus Cartridge Filter CCP520 10-20 PSI (Depending on the pump cycle - it actually has one cycle at night at 1500rpm that produces 4psi)
Filter was last cleaned about a month ago. I use an in-line basket to catch most debris when vacuuming.

 

[dcruff]

Thanks for the reply. I'll go ahead and check out the Thermal Regulator. Since there is no specific code or light on the circuit board associated with the thermal regulator, would it's failure set the Service Heater indicator?
Pentair Intelliflo VSF - I believe that it's 3HP (HHP:1.88 THP:3.95 WEF:6.9)
Pentair Clean & Clear Plus Cartridge Filter CCP520 10-20 PSI (Depending on the pump cycle - it actually has one cycle at night at 1500rpm that produces 4psi)
Filter was last cleaned about a month ago. I use an in-line basket to catch most debris when vacuuming.

I just pulled the Thermal Regulator and it was definitely in need of replacement. It's rusted out and permanently open. I just ordered a new one. $146 at the local pool supply, $29 on Amazon. Since the heater generally runs smoothly, I went for the on-line one, even though I know that it is 'aftermarket'. I guess that means that I need to watch my water chemistry better.
Again, could that trip the 'Service Heater' light?

 

[ajw22]

Test the thermal regulator in a pot of hot water and see if it opens at the temperature stamped on it.

We see many new ones who do not work properly.

 

[dcruff]

Just got my new thermal regulator and I'm now shipping it back. It didn't open until 190 degrees.

 

[ajw22]

Just got my new thermal regulator and I'm now shipping it back. It didn't open until 190 degrees.

Try a genuine Pentair Thermal Regulator even though some of them have failed test when new.

 

[JamesW]

If no error codes, then it is likely a flame sensing issue.

Check the Fenwal for three flashes of the LED.

Check the flame current.

Heater Flame Sensing - Further Reading

www.troublefreepool.com

 

[JamesW]

Exhaust Gas Temperature.​

While running, press and hold the On button to display the exhaust temperature (Older Models).

The new models use the Menu to get the SFS.

Here is what the normal exhaust temperature should be:

• Below 250 degrees...very low
• 250 to 290 ..................low
• 290 to 350.................acceptable
• 350 to 480 ..................high
• Above 480...................error/shutdown.

Note: HD models can be up to 75 degrees higher. HD models use a cupro nickel exchanger and the efficiency is slightly lower resulting in less heat transfer and more waste heat.

If the exhaust gas temperature is higher then normal then water may be bypassing the heat exchanger through a broken bypass valve.

If you hold down the "pool on" button, it stays on 80, then flashes to 40, then back to 80, then the 80/40 reading and E05 indicate that the board is not getting a reading from the sensor. It's usually a bad sensor or damaged wires.

 

[dcruff]

Try a genuine Pentair Thermal Regulator even though some of them have failed test when new.

Got my new Pentair Thermal Regulator at the local supply house, and it tested properly. I had reinstalled my old Regulator previously in order to keep my heater working, but apparently, in so doing, it fell apart and some of the larger pieces fell down the manifold. So, in order to retrieve the broken pieces, I had to remove the manifold, which required removing some of the plumbing. When I removed one of the pipes, I found a large piece of the Manifold Bypass Valve sitting in the pipe next to my chlorinator - just sitting there. Once I found out what it was, I went back to the pool supply house and purchased a Manifold Bypass Valve Kit.
The manifold came off simply enough, and the new pieces installed simply. I lubricated all of the o-rings and threads, put it all back together and now it runs wonderfully - no 'Service Heater' light. It probably runs way more efficiently now too.
Moral to the story - don't scrimp on the parts. Pay the big bucks when necessary. If the thermal regulator doesn't have the temperature stamped on the unit, it's from China and will not work.

 

[ajw22]

Check the manifold bypass would have been my next suggestion.

FYI, the heater would have run without the thermal regulator in place.

Those are the two most common failures on the MasterTemp heater.

 

[JamesW]

What is the stack flue temperature?