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Thread: Heater Won't Shut Off

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    gfurman's Avatar
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    Heater Won't Shut Off

    I have a Pentair 150M CH MiniMax milivolt heater that won't shut off after its been running for a while. About 4 years old. Any help would be appreciated.heater.jpg
    24 ft round 52" >14,600 Gal > Above Ground > Pentair Optiflo 2-speed 1-hp pump > cartridge / DE filter > Pentair 150M MiniMax CH Milivolt Natural Gas Heater > TF-100 Test Kit

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    Richard320's Avatar
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    Re: Heater Won't Shut Off

    Sounds like a bad thermostat. It's going to keep running until it reaches the temperature you set it at, and if it doesn't think it's there, it won't shut off.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    Re: Heater Won't Shut Off

    Thanks for your reply,

    Except the on/off switch won't shut it down either...I have to cut the gas off.
    24 ft round 52" >14,600 Gal > Above Ground > Pentair Optiflo 2-speed 1-hp pump > cartridge / DE filter > Pentair 150M MiniMax CH Milivolt Natural Gas Heater > TF-100 Test Kit

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    Re: Heater Won't Shut Off

    The schematic is in the manual if you're handy with a DVOM. http://www.pentairpool.com/pdfs/Mini...PowerMaxIG.pdf

    If DVOM is an alien term, you're not handy with one.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Heater Won't Shut Off

    That heater is a lot older than 4 years.

    Sounds like someone bypassed some safety.
    Paul
    http://www.gastekservices.com A word of caution: When working with gas and electrical you might want to consider a licensed contractor. Consider the value of your life and others around you. If you would like to provide a review of the help I provided, please use the following link to leave a review. gastek - Google Search,

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    Re: Heater Won't Shut Off

    I bought it new in Sep 2009, so the first time I used it was spring 2010....so five years I guess....

    I'm handy mechanically to a degree and can replace parts....DVOM is indeed alien....some kind of meter?
    24 ft round 52" >14,600 Gal > Above Ground > Pentair Optiflo 2-speed 1-hp pump > cartridge / DE filter > Pentair 150M MiniMax CH Milivolt Natural Gas Heater > TF-100 Test Kit

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    Re: Heater Won't Shut Off

    DVOM = digital volt ohm meter.

    I was inside one of these last year and it seems there is a small board, if my memory is right, that has all of the connections for the thermostats, on/off switch and the millivolt connections for the gas valve. Maybe something amiss on that. Definitely sounds like there is a short in the wiring somewhere before the thermostats if switching off won't fix it.
    Unknown make 18' above ground (bought used in 1999) Sparco sand filter. Hayward 100,000 BTu heater. 2 speed pump

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    Re: Heater Won't Shut Off

    I missed the part about the on/off switch not shutting it down. Sounds like the control board is bad. Like danpik said, it's behind the knobs. I think you can still get this part.
    Paul
    http://www.gastekservices.com A word of caution: When working with gas and electrical you might want to consider a licensed contractor. Consider the value of your life and others around you. If you would like to provide a review of the help I provided, please use the following link to leave a review. gastek - Google Search,

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    Re: Heater Won't Shut Off

    I am thinking this is the part you "may" need...
    Amazon.com : Pentair 471677 Millivolt Electronic Thermostat Replacement MiniMax CH and Plus Pool/Spa Heater : Outdoor Spas : Patio, Lawn Garden
    Checking the circuits with a meter would verify this. I would also check the entire unit for some bad wiring that may have been chewed on by critters.
    Unknown make 18' above ground (bought used in 1999) Sparco sand filter. Hayward 100,000 BTu heater. 2 speed pump

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    Re: Heater Won't Shut Off

    First, see if the thermostat select switch is even hooked up. If it is, disconnect it and see if the heater then shuts off. If it does, you either have a bad switch, or bad thermostat(s) or maybe the water is so cold that the temp setting wont go below the current water temp. What is the temp of the water?
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    Re: Heater Won't Shut Off

    The water temp is 88...I have no problem turning it on...
    Thanks for the suggestions...I will get in there tomorrow and take a look at this board and the wiring. Thanks also for the part on Amazon...really appreciate the help fellows...
    24 ft round 52" >14,600 Gal > Above Ground > Pentair Optiflo 2-speed 1-hp pump > cartridge / DE filter > Pentair 150M MiniMax CH Milivolt Natural Gas Heater > TF-100 Test Kit

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    Re: Heater Won't Shut Off

    Wait, Ok the only way to tun it off is the gas valve? Which valve? The one outside of the heater? or the valve inside with the wires and pilot tube coming out of it. Either way, i think the gas valve may be sticking. This time, try unplugging the wires from the gas valve to get it to shut down. If it remains on, its the gas valve.
    Factory Warranty Station for:
    Jandy/Zodiac, Pentair, Sta-Rite, Raypak, Polaris,
    and Paramount pool cleaning systems.

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    Re: Heater Won't Shut Off

    Quote Originally Posted by Pool Clown View Post
    Wait, Ok the only way to tun it off is the gas valve? Which valve? The one outside of the heater? or the valve inside with the wires and pilot tube coming out of it. Either way, i think the gas valve may be sticking. This time, try unplugging the wires from the gas valve to get it to shut down. If it remains on, its the gas valve.
    Good thought...A volt meter would also be able to confirm if the power is being cut to the valve when the heat is satisfied.
    Unknown make 18' above ground (bought used in 1999) Sparco sand filter. Hayward 100,000 BTu heater. 2 speed pump

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