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Thread: Spa temperature Rise

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    Spa temperature Rise

    Construction of my in ground gunite pool and spa completed recently. We fired up the 1000 gallon spa this last weekend and notice a 20degree/hour rise in the spa temp. So it took about 2 hours to rise from 62degrees to 100. This seems a little slow to me. Does anyone feel if this rate of rise is typical for a 1000gal spa? There was no wind and the outdoor temp was 68 and no cover. My heater is a Jandy LRZ 400k BTU propane with a Jandy ePump running at the time at 3000rpm.

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    Mod Squad jblizzle's Avatar
    Join Date
    May 2010
    Tucson, AZ

    Re: Spa temperature Rise

    Well, 1 BTU raises 1 lb of water by 1 deg F.
    You have 8330 lbs * 38 degrees F = 316,540 BTUs

    Assuming your heater is 85% efficient it puts out 340,000 BTUs/hr

    So ideally it would take a little less than an hour. But this does not account for loses into the ground from the pipes and the spa surface and loses to the cold air above the spa.

    So, is it reasonable? ... maybe. But, what could you possibly do to improve the performance?
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    Join Date
    Jul 2013
    Mesa, Arizona

    Re: Spa temperature Rise

    I have a spillover spa, heated with an electric heat pump. Right now the unheated temperature of the water is about 60F, 2 hours on the button has been my average time to heat up to 100. Also a 1000 gal spa.......

    But yes, I would think a gas heated spa would typically take less time than that.....
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    mas985's Avatar
    Join Date
    May 2007
    Pleasanton, CA

    Re: Spa temperature Rise

    Ideal heat gain is about 40 deg/hr and you are getting about half that so either you are losing a lot of heat somewhere or the heater isn't working properly. I get pretty close to ideal heat gain in my spa. I would check to make sure all the burners are firing although with most heaters, it should alarm if it wasn't. Spiders like to make webs in the gas nozzles which can obstruct the flow some and make the heater inefficient.
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    ps0303's Avatar
    Join Date
    Jul 2011

    Re: Spa temperature Rise

    2hrs is way too long. I would get your builder and or the person that installed the heater out to figure out your issue. My first hunch is that you might not have "isolated" the water in the spa and that you were heating some of the pool water as well. Do you have a spill over into the pool? If so, was it spilling over into the pool while you were trying to heat just the spa?
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    Re: Spa temperature Rise

    I'm certain the pool water is isolated and there is no spill over. I had a quick conversation with the builder and he thinks the temp rise is about normal. I totally disagree with him, but I'm waiting to get all my facts inline before further conversations.
    The builder did say they did not do a temp rise check at the heater manifold as per what the heater manual says you should do. I think doing that will tell you if there is some sort of problem with the heater. Maybe the internal bypass at the water inlet header needs adjustment. Also, there is some sort of rattle coming from the inlet header. Wonder if something broke inside there.

    I did remeasure my spa and calculated the volume to make sure it matched what the builder says it was. It was right around 1000gals.

    Thanks all for the input

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