Question about Pentair Mastertemp Heater

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I have a Master temp 400. The temp sensor on the heater says water temp is 102 but measures only 95 degrees.I think the sensor needs calibration. Is this possible? Thanks

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  • Pentair Master
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New sensor

Posted on Oct 07, 2017


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SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

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Posted on Jan 02, 2017

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SOURCE: Heater shuts off 10 degrees before pool reaches the set temp.

The thermistor is probably failing and needs to be replaced. You can probably replace it yourself. We sell the part at

Posted on Jun 14, 2009

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SOURCE: Pential Easy Touch Pool/Spa remote says the water

you can change the calibration on the temp. or how did you check the sensor

Posted on Oct 05, 2009

  • 990 Answers


Inside the water manifold their is a by-pass asembly that may be the problem. If this is bad it will let to much water go past the heater rather than through it. The water inside the heater overheats then shuts the heater down more cool water workes it's way into the heater and it starts again. You may also have a by-pass valve on the plumbing going to the heater, this will give the same problem if not closed enough. You will find it in between the inlet and outlet pipes and it should be closed 80-90% of the way. I hope this helps, good luck.

Posted on May 21, 2010

  • 310 Answers

SOURCE: Have a brand new Master Temp 400K Propane with an

If this heater has pool mode and spa mode as an option, and you need the water higher than 84 degrees, you must set it to spa mode even if it is a pool. As a regulation, these heaters come pre-set to max out at 84 degrees as a safety feature. However, in spa mode it can reach 104degrees.

Posted on Jan 11, 2011

Testimonial: "Thank you, I will try that tomorrow!"

  • 4 Answers

SOURCE: have pentair easy touch controls just installed

Go to "calibrate" on your new unit and lower the spa "set at " temp a little

Posted on Dec 15, 2012

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1 Answer

Just installed new rs8pcb and temp sensor. Set at 104,only reaches 102, why?

Try calibrating your Jandy controller to the temperature of the heater. Temp sensor could be off by two degrees

Dec 04, 2016 | Pool & Spa

1 Answer

Master Temp 400 reading 32 degrees on LED read out and the remote control is reading 62 degrees. What can cause the difference?

The control panel has its own temp sensor which is a probe into your plumbing. It's typically found between the pump and the filter and is held on by band clamps.

The heater has its own temp sensor found on the header manifold area.

i doubt the water is 32 degrees so I assume the heater temp probe is bad, it needs to be replaced, it's plugged into the circuit board and threaded into the header of the heater.

The two sensors should match or be within one degree of each other for ideal operation.

The reason they have separate temp sensors is to protect the system.

Nov 26, 2016 | Pool & Spa

1 Answer

Pentair 400 2 yrs old won't heat spa to 98 degrees F.

This could be a number of things. Most often it will be the internal by-pass. You find the assembly inside the water header, it controls water flow through the heater. When it goes bad it can open at a low temp and keep the water from going through the heater.
Also you will want to check the temp probe on the side of the header. If this is bad it will usually show up on the temp display though.

Nov 18, 2010 | Pentair MASTER TEMP HEATER 400 000 BTU NG...

1 Answer

I have a minimax ch 150 heater and the heater is running but the water coming out is not as hot as it used to be. Though the heater is extremely hot on the outside. Any tips?

Check your SENSOR. With the Minimax ch heater, you might be using an 'IntelliTouch' panel that controls your equipment. If you are, check the reading that the panel says the water temperature is and then check the temperature of the water 'coming out' (spa??) manually with a floating thermometer. When the heater cycles off, check the difference between the 2 numbers. Say the panel says 102 & the thermometer says 95?? - that is a faulty sensor, telling the heater that the water has reached 102, so it cycles off before ever getting hot. If you're not using the IntelliTouch, you will be checking the display panel on the actual heater itself & again the floating thermometer. Now... if the temperature is less than a 4 degree difference you can always calibrate/or have calibrated the heater.

Aug 03, 2010 | Pentair MINIMAX NT TSI IGNITER

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