New to TFP - SFS error on Mastertemp 250 :(

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CBA-PoolDad

CBA-PoolDad

Member
May 28, 2023
17
NW Ohio
Hi all! I'm wondering if anyone could help point me in the correct direction. Here's what I have so far:

- 3 year old system has been working well until now (no signs of mice inside)
- Heater ignites, and I get an SFS error about 15-45 seconds later bc it was quickly heating to over 400 degrees and staying there
- I replaced a corroded thermal regulator with a brand new one that worked under hot water from a faucet (and I know our pool company has done this a few times already this year, so I was hoping this would fix it)
- I replaced it yesterday and couldn't wait to watch the heater work again!! But it didn't, and I get the same SFS error and heater shuts off :cry:
- I see the next thing mentioned on the flow chart is "Check Heat Exchanger Coil for leaks, liming, soot, or low flow" - I'm not really sure how to go about this, but here's my pool system to review:

- Is it possible I installed the thermal regulator wrong? I did it exactly like the other, and tried it 3 times :ROFLMAO:

Any help would be suuuuper appreciated as I'm a pool dad trying to get the pool ready for the family :)

Thanks!
Adam

IMG_2077.jpegIMG_2075.jpegIMG_2076.jpeg
 
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.

If the SFS reads 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.

Try reseating the connectors on the SFS.

Otherwise it's a bad sensor or damaged wires.

If the sensor and wiring are good, the board is probably bad.

Disconnect the sensor and check continuity across its terminals.

Resistance should be 3.5-4.0 megaohms.
 
Remove the thermal regulator and test it in water that is 120 to 125 degrees to see if it opens.

When you remove the thermal regulator, take a picture looking into the hole and show the top part of the hole to see if the internal bypass disc is in place.

Run the heater without the thermal regulator in place to see what the Stack Flue Temperature goes to.

Can you show a picture looking into the heater inlet?

1685286616229.png

1685286640230.png
 
Check the cell to see if this piece is in the cell.

1656268549999-png.428753
 
Replace the SFS. We are seeing a lot of failures of them after a few years of operation.

You can spend a lot of time with diagnostics or just replace the sensor and see if it fixes the problem.

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com www.troublefreepool.com
 
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JamesW said:
Remove the thermal regulator and test it in water that is 120 to 125 degrees to see if it opens.

When you remove the thermal regulator, take a picture looking into the hole and show the top part of the hole to see if the internal bypass disc is in place.

Run the heater without the thermal regulator in place to see what the Stack Flue Temperature goes to.

Can you show a picture looking into the heater inlet?

View attachment 497158

View attachment 497159
Click to expand...
Hi James,

Thanks so much for the replies! Here's some more info:

- New thermal regulator opens under hot tap water from kitchen faucet (I honestly didn't measure 120 degrees, but it definitely opens...my old one was corroded and green)
- Here's a picture inside regulator pipe:
adams reg pipe.jpeg
 
Looks like the internal bypass is OK.

Likely to just be a bad SFS.

Disconnect the sensor and check continuity across its terminals.

Resistance should be 3.5-4.0 megaohms.
 

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CBA-PoolDad said:
Hi James,

Thanks so much for the replies! Here's some more info:

- New thermal regulator opens under hot tap water from kitchen faucet (I honestly didn't measure 120 degrees, but it definitely opens...my old one was corroded and green)
- Here's a picture inside regulator pipe:
View attachment 497164
Click to expand...
JamesW said:
What is leaking in the picture near the cell?

What is the filter pressure?

What is the pump speed?

View attachment 497162
Click to expand...
- I think that is just a little water that was leaking from the cell
- Filter pressure: I've back flowed and get no errors about high pressure, but unfortunately my little gauge broke so I don't know for certain :(
- Pump speed is at 50 GPM when running heater
 
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ajw22 said:
Replace the SFS. We are seeing a lot of failures of them after a few years of operation.

You can spend a lot of time with diagnostics or just replace the sensor and see if it fixes the problem.

Click to expand...
JamesW said:
Remove the thermal regulator and test it in water that is 120 to 125 degrees to see if it opens.

When you remove the thermal regulator, take a picture looking into the hole and show the top part of the hole to see if the internal bypass disc is in place.

Run the heater without the thermal regulator in place to see what the Stack Flue Temperature goes to.

Can you show a picture looking into the heater inlet?

View attachment 497158

View attachment 497159
Click to expand...
Question: is it safe to do this? I'm just not smart enough about this system :) Also: can you run the heater for like a few days without the thermal regulator in place? Or maybe if the SFS is bad, it wouldn't work anyways?
Run the heater without the thermal regulator in place to see what the Stack Flue Temperature goes to.
Click to expand...
 
JamesW said:
The thermal regulator just prevents condensation from forming on the heat exchanger when the water is really cold.

It is OK to test run it with the thermal regulator out.
Click to expand...
Thank you so much for the information. I ran the heater without the thermal regulator in place, and it went up to 480 degrees super quickly, so it looks like my next step is to replace the stack flue sensor and then try again!
 
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ajw22 said:
Replace the SFS. We are seeing a lot of failures of them after a few years of operation.

You can spend a lot of time with diagnostics or just replace the sensor and see if it fixes the problem.

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com www.troublefreepool.com
Click to expand...
Thank you for your reply - super helpful!! and it sounds like I will start here, esp. since it's a pretty cheap part to replace :)
 
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