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Billy
Billy, Technician
Category: Pool and Spa
Satisfied Customers: 22429
Experience:  Licensed in Hydronics and Boilers
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Garry I have a pentair MT 250 that is giving me fits. I just

Customer Question

Hi garry
I have a pentair MT 250 that is giving me fits.
I just replaced the flue sensor due to having an E05 error, and that is now gone, but I notice that the unit seems to run intermittently now. It fires for a short time (a minute or so) then stops. NO error message other than the red service heater LED. After a couple of minutes the red LED goes out, it starts blinking heating, then it fires again and the cycle repeats... It will eventually heat the hot tub, but it takes much longer than it used to/should.
Any suggestions?
Phil
Submitted: 1 year ago.
Category: Pool and Spa
Expert:  Billy replied 1 year ago.

I am very sorry your question has not been picked up yet.

I just logged on and found you had not been assisted.

Please let me know if you still need help and I will do my best. Please do not "Rate" as we have not worked toward an answer yet.

If you would like to proceed let me know by replying. Once again use reply..not "rate".

Customer: replied 1 year ago.
If you are knowledgeable in the Pentair pool heater line, I would be happy to have you assist me. This is my first time using this site, so I am kind of new to the ins and outs of how it works. I addressed the original to "garry" because his name was in the post that came up in my search result. I was trying to see if I could get this resolved without calling the 'local' pool company since the closest one is 35 miles away and not always able to get here in a timely manner. I will be around the computer on and off today until around 2 pm.
Expert:  Billy replied 1 year ago.

when the unit first kicks on...does it stay on or tries a few times before it keeps running?

Is the pump moving water as it usually does or a bit slower?

Customer: replied 1 year ago.
Pump runs fine, overflow from hot tub to pool running with normal volume when it is pulling from pool/dumping in hot tub. hen it kicks on, the heater light (yellow) turns on, then it goes "whoosh" and starts to heat within 15-30 seconds. It runs for a minute or so, the heat turns off, fan continues to run and red "service heater" light goes on. After 30-60 seconds or so, the red light goes off, the heater light starts to blink, then it cycles back through the same process again. It will eventually get the hot tub up to temp, but it takes a lot longer (since it is only heating half the normal time (or less), and I assume each time I let the chamber cool down I am losing heat and therefore efficiency.
Customer: replied 1 year ago.
BTW I just backflushed the filter a few days ago to be sure it was clean, and it didn't change anything
Expert:  Billy replied 1 year ago.

Ok, hows the burner assembly look? any rust?..If we get a poor burn the unit can drop out on flame sense

Customer: replied 1 year ago.
How do I get into the burner assembly? There is a tub at the bottom of the unit with some rust on it, but not sure where the burner assembly is or how to get into it. BTW the unit is about 3 1/2 yrs old if that makes any difference.
Expert:  Billy replied 1 year ago.

see page 51 HERE