Run MasterTemp heater without thermal regulator?

[JT8Diesel]

I'm trying to eke out a few more days at the end of the season, and it appears my heater has decided to not cooperate.

It recently started cutting out with the red "Service Heater" LED illuminated. Looking on the back of the control board I see a SFS LED illuminated. Following the troubleshooting steps, and the first thing is to check the thermal regulator. I've removed it and it doesn't open at 120º, opens a hair at 125º and appears fully open at 130º

As background info, my pool was installed in Spring 2020 and the heater always seemed to run "hot." I'd have the Intellicenter set to say, 84º and the display on the heater would routinely be up to 20º higher than my desired, despite the pool not being that hot. I just realized yesterday, that the plumbing was actually BACKWARDS. So water was ENTERING the heater at the OUTLET, and EXITING through the INLET.

I've fixed the plumbing, and I don't see that crazy delta anymore, but after 10-20 minutes the heater shuts down with the SFS error.

Since the plumbing was reversed, I'm wondering what other damage / problems could have been caused.

1. My thermal regulator remains closed at 120º but seems to start at 125º and is open at 130º. Is that "bad enough" to cause a problem?
2. What else should I look for due to backwards plumbing?
3. Can I run the heater without the thermal regulator for a few days until I get a new one in the mail? In the meantime I'm at least running the pump and filter.

Thanks all!

 

[JamesW]

While running, press and hold the On button will display the exhaust temperature display.

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.

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

 

[JamesW]

Do you have pictures of everything?

 

[JT8Diesel]

While running, press and hold the On button will display the exhaust temperature display.

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.

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

I've seen this done on other MasterTemp's, but doesn't seem to be an option on mine. I don't get the temperature read-out. I do have a thermocouple for my multimeter, and exhaust temp seemed to be around 380, so high. But invariably I'm not around when it gets high enough to trip off.

Do you have pictures of everything?

I think so, anything in particular?

 

[JamesW]

I've seen this done on other MasterTemp's, but doesn't seem to be an option on mine.

The new models use the Menu to get the SFS.

https://www.pentair.com/content/dam/extranet/nam/pentair-pool/residential/heaters/mastertemp/manual/Manual-MasterTemp-472592-English.pdf

 

[JamesW]

I think so, anything in particular?

The whole system from several angles.

 

[JT8Diesel]

The new models use the Menu to get the SFS.

View attachment 456366

https://www.pentair.com/content/dam/extranet/nam/pentair-pool/residential/heaters/mastertemp/manual/Manual-MasterTemp-472592-English.pdf

View attachment 456367

Well I have the five button panel, so it's not the "connected" version and no menu. BUT, also holding "Pool On" doesn't result in any display change?

The whole system from several angles.

Yes, I have, would you like me to post them here?

 

[JamesW]

Well I have the five button panel, so it's not the "connected" version and no menu. BUT, also holding "Pool On" doesn't result in any display change?

Try Spa Mode.

Maybe the Membrane pad is going bad and the "Pool On" button does not work?

Are you pressing the Pool On button if in Pool mode or the "Spa On" button if in Spa mode?

Are you pressing for at least 5 seconds?

Yes, I have, would you like me to post them here?

Yes.

 

[JT8Diesel]

Try Spa Mode.

Maybe the Membrane pad is going bad and the "Pool On" button does not work?

Are you pressing the Pool On button if in Pool mode or the "Spa On" button if in Spa mode?

Are you pressing for at least 5 seconds?

Yes.

The "Pool On" button works. I can switch from Pool to Spa modes. Weird. I just tried again, and holding "Pool On" doesn't work, but switching to Spa and then holding "Spa On" does. It's showing 428º right now (reinstalled old thermal regulator). Here are the "overall" system pictures. This is AFTER I switched the INLET/OUTLET plumbing on the heater.

 

[JamesW]

Remove the thermal regulator and then recheck the SFS.

 

[JamesW]

Look into the hole where the thermal regulator goes and see if the internal bypass looks ok.

You can also see the internal bypass if you look into the inlet.






You can unscrew this piece to get a better look.

 

[JamesW]

The thermal regulator just helps prevent condensation.

You can "probably" leave it out as long as there is no condensation on the pipes.

However, since the heater is designed to operate with the thermal regulator, I am not going to recommend or even suggest that it is OK to operate with the part left out.

The main thing is if condensation drips into the heater and causes water damage.

If you want to leave it out, that is your choice and your risk based solely on your assessment and your determination.

There might be some reason we are not aware of that might be a reason that it should not be left out.

 

[JT8Diesel]

Remove the thermal regulator and then recheck the SFS.

I ran it without, and it tripped off on SFS again. Water could be bypassing most of the heat exchanger with it like that…?

I will take a look inside and see if I can check the bypass valve.

Thanks for the help. I’ll update tomorrow once I have some light to work on it.

 

[JamesW]

I ran it without, and it tripped off on SFS again.

Did you check the SFS temperature?

 

[JamesW]

Are you getting at least 40 GPM?

 

[JT8Diesel]

Are you getting at least 40 GPM?

Mastertemp manual shows min of 25 GPM for the 200. My pump runs at 2000 RPM / 32 GPM normally, and 2500 RPM / 44 GPM with the heater on.

 

[JamesW]

Check the internal bypass and run the heater with the thermal regulator out and check the SFS several time to determine where the shutdown happens.

 

[ajw22]

You can monitor the exhaust temperature using an IR thermometer and it will be about 10% below the SFS...

 

[JT8Diesel]

I removed the TRV and took photos inside both that and the inlet. I've included them here. All looks "ok" to me.

I then ran it without the TRV. I manually shut it off at 1050 / 475º since the writing was on the wall at that point. Of note, my pump was running 2500 RPM / +/- 45-ish GPM, water temp was 60º.

Time	Stack Flue Temp
1017	289º
1020	349º
1025	359º
1030	379º
1035	424º
1040	435º
1045	446º
1050	475º

 

[JamesW]

I suspect that the heat exchanger is probably scaled and/or sooted.

I would check the exchanger and clean it inside and outside.