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Thread: Hot tub won't heat past 95 degrees.

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    Join Date
    May 2016
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    Clarksville, TN
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    Hot tub won't heat past 95 degrees.

    Hello, I have a 2002 Viking Supreme hot tub. Six person 300 gallons. I hooked it up, filled it up, and fired it up. Everything worked fine. Circulation pump ran fine, all jets worked fine, and temperature went from 65 to 104 degrees within about 8 hours. That's when I noticed the leak. The water was leaking out around the temp sensor probe connection. I drained the pool and pulled off the spray foam around the sensor. I put a generous amount of silicone around the threaded part that enters through the pool. Leak stopped. I put another styrofoam cup over the probe and sprayed on some new foam. I filled the tub back up and turned the power back on. Everything seemed to be working until I noticed it wasn't heating up. After a week it is up to 95 degrees. I checked the voltage on the heat element and I had 120 volts on EACH side from ground to each leg. I read somewhere that said I should have 240 volts between them, but when I put the probes on both legs it reads 0. I checked to make sure the temp was set to 104 and it was. I assume the probe is ok because the water "feels" 95 and it reads 95. I took the filter out and let run overnight to make sure we have good flow. No change. Any suggestions?

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    cowboycasey's Avatar
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    Jul 2013
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    Re: Hot tub won't heat past 95 degrees.

    Welcome to TFP

    it sounds like the temp sensor but you say it reads 95.. try below and see if any of that helps...

    Found this in the manual (well the 2005) Download Owners Manual | Viking Spas - Premium Hot Tubs
    Spa Will Not Heat
    Check For Air Lock
    • Is this a new installation with trapped air?
    Solution; Open drain hose and cycle pump to high speed for approximately
    30 seconds or open bleed plug on face of pump for same
    amount of time.
    • If not, has the spa been drained and refilled?
    Solution; Make sure water level is at mark on skimmer.
    • Is there proper water flow?
    Solution: Make sure both Gate Valves are open and filter is clean.

    Contact Your Authorized Spa Retailer for Service.
    Pool: Intex 16x32 15000 gal, 2 speed 340042, Pentair CC320 Filter, CircuPool SJ45 Salt System, Intermatic PE653RC; Hot Tub: 650 Gal SWG Megachlor
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    Isaac-1's Avatar
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    May 2010
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    Re: Hot tub won't heat past 95 degrees.

    I had a similar issue on my Hot Spring tub, the problem was low flow on the circulation pump causing the heater to trip off on overheat.
    Indoor 20x40 35,000 gallon vinyl pool with 1.5 HP 2 speed Jandy FloPro pump, Hayward EC75 Perflex DE filter, 11 4x12 Techno-Solis solar panels w/ Aquasolar controller, Aquabot Turbo T Robot Cleaner. Also LMI metering chlorine dispenser pump and HotSpring Jetsetter
    I use and endorse TFtestKits TF-100 from http://tftestkits.net
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    Join Date
    May 2016
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    Clarksville, TN
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    Re: Hot tub won't heat past 95 degrees.

    I replaced the heater element and the spa still won't heat up. Is there something on the main board that i can check? All of the fuses checked good for continuity. The water coming out of the jets is not "cold" but it is definitely not warm either. when the weather was in the 70's and up the spa would cut off when the desired temp was reached, but now that it is in the 40's and below it won't heat up at all. It has a brand new cover on it.

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    dsmith99's Avatar
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    Re: Hot tub won't heat past 95 degrees.

    Quote Originally Posted by Darkie14 View Post
    I checked the voltage on the heat element and I had 120 volts on EACH side from ground to each leg. I read somewhere that said I should have 240 volts between them, but when I put the probes on both legs it reads 0.

    When testing each leg separately you will read 120 volts even if one leg has dropped out. This happens because power feeds through the heater back into the other leg of the circuit. You must test across the heater leads, that is the only way to verify the heater is receiving the full 240 volts.

    A reading of zero means the heater should not be working at all.

    Even though you have 120 volts present at the heater, it is not usable without completing the circuit. A complete circuit requires phase to neutral for 120v or phase to phase to produce 240volt. I would start at the source, make sure you have 240 volt testing from phase to phase and go from there. If you are not completely confident in your ability to test and diagnose, please call in a qualified electrician.
    AGP 24' x 54" approx 14000 gal Full sun all day, Hayward 1.5 HP and EC50 D.E. filter
    Stenner 45MPHP10 10 gal/day fixed rate with intermatic ET1125C timer
    Dolphin E10 robotic cleaner, 330 gallon Tiger River Spa, Taylor K-2006C test kit

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    Re: Hot tub won't heat past 95 degrees.

    I would suspect that the breaker to the heater has failed.

    There should be a breaker box near the hot tub.

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