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Thread: Pentair Minmax Plus 400 Pool Heater Issue

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    Pentair Minmax Plus 400 Pool Heater Issue

    I'm wondering if anyone has run into this problem...

    I have a 11 year old Purex Minmax Plus 400 Pool Heater which is cycling on and off. Here are the symptoms

    When turning on the heater it will run for a few minutes normally and then shut off with the service light on. When this occurs I hear a clicking noise coming from controller module (not the igniter). If I turn off the heater for a short period of time (10 mins) and then turn it back on. The heater runs for a bit and then shuts off again with the clicking noise. This almost seems as if there is some sort of thermal / overheating issue occurring.

    If I do not turn off the heater, the igniter in the unit remains hot and the unit does not turn back on. It is only when I shut the heater off for a short period of time that I can get it to restart and run again for a little bit.

    This is what I have done so far...

    1) I have backwashed the DE filter and also place the filter in recirculate mode. Same problem occurs
    2) I have replaced the control module. The problem still occurs.
    3) I have tried cleaning out burners by blowing compressed air through them. Still the same issue

    Does anyone have any thoughts on anything else that I can check or do?

    Thanks in advance!!!
    Bob
    13x25 SplashPool (10,600 gal) AG
    20" Sand Filter with 1HP pump

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    JasonLion's Avatar
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    Re: Pentair Minmax Plus 400 Pool Heater Issue

    Welcome to TFP!

    Does the heater display an error code when it shuts off?
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: Pentair Minmax Plus 400 Pool Heater Issue

    Welcome to TFP!!

    It's probably the AGS switch, (it could also be that you don't have enough gas to feed the heater) I"d say it's the AGS
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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    Re: Pentair Minmax Plus 400 Pool Heater Issue

    When this problem occurs the following status lights are lit

    TSTAT - On
    Aux - On
    Pressure - On
    Heat - Off

    Power - On
    Service - On

    From the Minmax Plus Owner's Manual that I found online states that the issue is the TFuse. However, looking at the TFuse it looks ok, and I would think that it blew due to over heating that it would remain off.

    I did do another test, where I moved the TFuse from inside the unit to outside the unit (leaving the access panel off) and the problem still occurred.
    13x25 SplashPool (10,600 gal) AG
    20" Sand Filter with 1HP pump

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    Re: Pentair Minmax Plus 400 Pool Heater Issue

    Quote Originally Posted by waste
    Welcome to TFP!!

    It's probably the AGS switch, (it could also be that you don't have enough gas to feed the heater) I"d say it's the AGS
    What is the AGS switch? Is that the pressure switch?
    13x25 SplashPool (10,600 gal) AG
    20" Sand Filter with 1HP pump

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    Re: Pentair Minmax Plus 400 Pool Heater Issue

    A bit more information... I did some more testing and tinkering with heater and I think I have come to the conclusion that it may need to be completely replaced.

    With the front cover off exposing the burners, I fired up the heater. As expected it ran for about 5 to 10 mins and then shut off. However, this time I noticed some sizzling sounds coming from the heater. On closer inspection I saw that there was some water that would drip onto the burner. When the water dripped onto the pilot/igniter it would put it out, thus shutting the heater down and preventing it from restarting until it was dry again.

    So this looks like the manifold on the inside of the unit has a leak, either corroded, cracked, or broken seal. When heater is not running there are no leaks, no drips, or water wet spots underneath the heater. It only seems to occur when the heater is on. So it is making me believe that the leak is caused due to expansion of the manifold (due to heat) or increased pressure in the heater (due to heat).

    Right now I am not sure if want to attempt to take apart the heater to replace the manifold or just replace the entire heater since it is now 11 years old.
    13x25 SplashPool (10,600 gal) AG
    20" Sand Filter with 1HP pump

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    In the Industry

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    Re: Pentair Minmax Plus 400 Pool Heater Issue

    If the water is cold, the dripping you are seeing while fired is likely condensation. Typically the pilot lights have a drip shield to protect them from getting put out, but often times the drip shield corrode and disappear.
    20X40 30,000 gallon gunite pool

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    Re: Pentair Minmax Plus 400 Pool Heater Issue

    May I ask a question?

    Before you found us, did you use chlorinating pucks for many years and not keep up on the pH?

    Do you see water puddling or running our of the bottom of the heater?
    Luv& Luk
    -Ted

    Having done construction and service for 4 pool companies in 4 states starting in 1988, what I know about pools could fill a couple of books - what I don't know could fill a couple of libraries :-D

    POOL SCHOOL, TF Testkits, Jason's Pool Calculator, CYA vs. cl chart, (Just a few DARNED handy links!)

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