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Thread: Heater Turns on for 15 Seconds then Shuts Off

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    Heater Turns on for 15 Seconds then Shuts Off

    We have a two-year old pool with a MasterTemp 4000 gas heater. It had been working fine, but when we tried to heat the spa the other day the heater ignited, ran for 15 seconds then shut off. We have replaced the thermostat, a relay and the igniter, but the problem persists. Any thoughts?



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    coog61's Avatar
    Join Date
    Nov 2009
    Richmond, TX

    Re: Heater Turns on for 15 Seconds then Shuts Off

    Had the same problem with my variable speed pump. I had the pump running to low (~2,500 rpm). When increased to ~3,000 rpm, heater stayed on. The heater manual did say that low water flow will cause it to cut off.

    Good Luck
    17,500 Gallon, SWG 33' x 21' freeform w/ Sunstone Cobalt Plaster. Attached 6 X 6 Spa raised 12" w/ 6 Jets with Moss Rock Spillover. 25' Moss Rock Waterfall. Pentair Intelliflo VS-3050 for Pool, 2 HP Whisperflo for Waterfall, Pentair Clean & Clear Cartridge 320, Pentair 400K BTU Max-E-Therm heater, Pentair Intellichor, Pentair EasyTouch 4P, Pentair Legend Platinum Cleaner w/ 3/4 hp pump, autofill system, nat gas fire pit. BBB convert

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    Re: Heater Turns on for 15 Seconds then Shuts Off

    Hmmm, my pump is not variable that I know of. It's a 1.5 hp Whisperflo.

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    Melt In The Sun's Avatar
    Join Date
    Oct 2009
    Tucson, AZ

    Re: Heater Turns on for 15 Seconds then Shuts Off

    I agree that it sounds like a flow issue. It may seem like a dumb question, but are all the appropriate valves open? That pump should give you plenty of flow, unless there's a problem somewhere. Do you get decent flow at the returns?
    11,200 gal, Pebble-Tec; Tristar 2-speed 1hp - Swimclear 325 ft2 cart - SWG - A & A in-floor cleaner - Heat pump. For the poolside cooking, a Yoder Wichita and a Big Steel Keg!
    TF Test Kits -- PoolMath -- Pool School
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    JasonLion's Avatar
    Join Date
    May 2007
    Silver Spring, MD

    Re: Heater Turns on for 15 Seconds then Shuts Off

    I is possible that the heater needs to be cleaned. When the fire box vents get partially clogged by ash the heater will shutdown because it can't get enough air flow.
    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: Heater Turns on for 15 Seconds then Shuts Off

    If you bought three or more Pentair products at the same time you are still under warranty. You should not have to replace the thermostat, a relay and the igniter already.

    Sounds like you may have spider webs in the ports, or another build up. Did you pull the face piece and take a flashlight and look at the burner tray? I would take a look in there, as the fact that it is at least igniting tells me that everything is basically working.

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    Join Date
    Mar 2007
    Coastalish 'down easter'

    Re: Heater Turns on for 15 Seconds then Shuts Off

    Welcome to TFP!!

    Let me throw out my $.02 - check the thermal regulator, if it's shot cool water will not mix with the heated water and the temp will climb high enough to trip the high limit switch in ~ 10 - 15 seconds.

    Of course there are other possibilities, you can 'jump out' any suspect switches, rather than just blindly replacing parts
    Luv& Luk

    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: Heater Turns on for 15 Seconds then Shuts Off

    I'm with waste - sounds like a limit switch problem. If you are handy with an ohm/voltmeter, look at the wiring diagram and ohm out the limit and pressure switches.
    ~45Kg Pool with attached Spa, NSP-72 DE, Minmax 400 Heater, Tahoe Blue Pebbletech, Jandy SWG via Aqualink RS-8, The Pool Cleaner (black)
    Pumps: X3 Hybrid Pump (switches to SPA), 2HP Spa (additional, when SPA is on), and a 1HP For Waterfall
    8, 4x12 Solar Panels on the roof of the pool-house (~12' up)

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