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Thread: Heater pressure switch failure when changing from spa to pool

  1. Back To Top    #1

    Join Date
    Feb 2015
    Location
    California
    Posts
    11

    Heater pressure switch failure when changing from spa to pool

    Hi guys,
    I'm a new pool owner and my pool has all mechanical valves which I think I've sorted through enough to have half a clue what they do.
    The heater I have is a Pentair Minimax NT.

    This weekend was the first time I really tried to use the heater. I was successful in getting it to run when I have the valves configured to suck and fill from the spa only. When I changed this so that the overflow would flush into the pool, the heater through a code for the pressure switch, but then seemed to overcome that and turn back on.

    My goal ultimately was to heat up the pool a bit. So in my simple mind I thought perhaps it was more efficient to just run the pump to suck and fill from the pool only. At this point the heater would not stay functioning and light for the pressure switch would shut off.

    So ultimately I think I've concluded that my heater will not run when I'm only flowing water back into the pool.
    In this case it rules out anything upstream of the heater since everything is good when I'm pumping the hot water back into the spa (regardless of whether the spa drain is open, closed, partial). So what is going here? If it were a clogged filter it clearly wouldn't work in spa only mode....so I guess this says there's an issue with my feed line to the pool?
    24000 gallon plaster pool, DE filter, chlorinated pool, connected pool & spa with waterfall feature, all manual valves

  2. Back To Top    #2
    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
    Posts
    37,879

    Re: Heater pressure switch failure when changing from spa to pool

    Welcome to TFP!

    It could well be a dirty filter. A number of factors influence the pressure the heater sees, including pool or spa mode, filter status, valve positions, etc. The system will have a higher flow rate in spa mode than in pool mode, so if the filter was just dirty enough to fail in pool mode, it will still work in spa mode.

    There are several other possibilities, but restricted flow due to debris in the skimmer/pump strainer basket/filter is the most likely cause.
    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

  3. Back To Top    #3

    Join Date
    Feb 2015
    Location
    California
    Posts
    11

    Re: Heater pressure switch failure when changing from spa to pool

    Thank you! The big filter needs a clean, so I'll get on that this weekend and then report back.


    24000 gallon plaster pool, DE filter, chlorinated pool, connected pool & spa with waterfall feature, all manual valves

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