Question about Pentair Mastertemp 250 Natural Gas Pool Heater

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Mastertemp 250 power issue and service system only 8 months old initially turning on then from there a service system light and power distribution issue . Switched out ignition box and bad connector

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What is the current problem?

Posted on May 14, 2017

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Posted on Jan 02, 2017

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SOURCE: I have a Pentair MasterTemp Heater 250K BTU (i

try cycling the power to the heater itself. Check for damage (pack rats, etc..). It sounds like you may have had a direct short. It could be a board problem or a transformer problem. If you're still getting the service heater light, check to see if any diagnostic LED is illuminated behind the board.

Posted on Jan 19, 2010

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SOURCE: mastertemp 250 service system light

This has something to do with a water temperature sensor which normally is a thermocouple.It seems that yours is reading the water temperature,sends a feedback signal to some sort of computer type controller,and when the heater output water starts getting a bit hotter than the temperature which it knows the water currently is,it's shutting down.Within thermocouples,there is a small section known as a reference temperature.That section sounds like it's gone bad because when comparing the temperatures and going above the reference,the best way to describe it is it's like popping a circuit breaker in your house,which causes shutdown,but in your house it's to prevent fire and/or save the housing wiring.In the pool heater,it's saving the water from boiling because it doesn't know when to stop.If you need more help or this is not correct,just comment back here and I will get an autolink to your post and reply ASAP.Good luck! Greg

Posted on Oct 16, 2010

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SOURCE: Pentair MasterTemp 400 Heater Will run fine for

This reminds me of some of the High temp sensors ive replaced. I would start with checking the pumps flow to the heater. Make sure there are no abstructions and at least 35 GPM (gallons per minute) running to the heater. If your flow is too low, you will trip the high limit sensor after a short while.
This could also mean you need to clean out the heat exchanger. When an exchanger gets dirty, it blocks the flow of water, slowing it down and "super heating" itdue to the water being in contact with the exchanger for too long. This will also trip the high limit and call for service.
If both the above items check out, contact me @ and I will guide you further.

Posted on Nov 23, 2010

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SOURCE: MasterTemp 250 blowing breaker...

As a pool professional, i have yet to have this problem, and youve had this problem twice now. Have you looked inside the liquid tight flex or galvanized conduit at the wires feeding the heater? Water could be inside that line causing your power to short to ground. Id check there first.

Posted on May 21, 2014

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try cycling the power to the heater itself. Check for damage (pack rats, etc..). It sounds like you may have had a direct short. It could be a board problem or a transformer problem. If you're still getting the service heater light, check to see if any diagnostic LED is illuminated behind the board.

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Service light on

I just had the same problem resolved, my mastertemp 400 would run up the temp to 82F and then cutoff, the service light flashes and then 50 seconds later the heater would restart and run for 2 minnutesbefore shutting down again and relighting in 50 seconds. Repeating until the temp setting is reached.

I had the pool guy out 3 times until he found a bad thermal regulator valve (kit #77707-0010). Once replaced the heater runs great.

He told me that it's my pool chemestry that is to blame, I had it checked (like I do weekely by me and monthly by the pool supply store) and it perfect??? I'm now questioning what caused the corroson and stop it from coming back?

I hope tis helps.

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