Pentair MasterTemp Heater Turns on by Itself

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Silver Supporter
Apr 12, 2016
95
Philadelphia, PA
Pool Size
28000
Surface
Plaster
Chlorine
Liquid Chlorine
I have a Pentair MasterTemp 300k natural gas heater. This is the second time this has happened. With the OEM equipment, after about a year or so, the LCD on the control board starting glitching and then eventually I noticed it start turning on by itself. Ok, control board bad, sucks, but is what it is. Bought a new one. And yes, because they are ridiculous in price, I bought an aftermarket control board ($220 vs $450+). That was four months ago. I go to turn on my pool pump this morning getting ready to close the pool and as soon as I do, my pool heater also turns on automatically. No lights on the pool heater and the buttons don't do anything. Nothing on the LCD. I have to turn off the gas line to get it to stop (no hardware switch just for the heater). Then.... I check the water... my 30,000 gallon pool is over 100 degrees. FML.

Over $100 in natural gas out the window. This happen to anyone else?? Obviously, I am going to need to install a hardware switch for the dang thing now.
 
Last edited:
It is usually the membrane keypad keys that stick on. The membrane keypad can be replaced separately from the PCB.

Install a toggle swithc at the Fireman's switch jumper to have a physical ON/OFF switch.
 
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