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Thread: Time to heat up spa

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    Time to heat up spa

    Hi all,

    I just bought a house with an inground pool and attached spa. I'm curious how quickly the heater *should* heat up the spa. Its not small, but it's not huge either. Just a good size. I have a Hayward H400 heater. This morning, I attempted to heat up the spa, and it went from 71 to 75 in maybe 30-40 minutes. That seems awfully long for a 400k BTU heater. What do you all think?

    Thanks much in advance!
    Approx 25k gallon PebbleTec in-ground diving pool and attached raised (10 person?) spa, with spillover and waterfall.
    Hayward AquaLogic PS-4 control board, Hayward SP3400VSP Ecostar pump, Hayward C5520CP cartridge filter, Hayward H400FDN 400k BTU NG heater

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    Re: Time to heat up spa

    It is more a function of flow through the heat exchanger than BUTs. Are you using one pump for the spa and pool? Or is there separate pump for the spa?

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    Re: Time to heat up spa

    Post your question only one time. Regardless of the forum, all will se it and it will save a lot of confusion.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Richard320's Avatar
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    Re: Time to heat up spa

    Doublecheck the valves. That sounds like you're heating the pool, too.

    I can bring my 7' diameter spa from the mid 60s to 100 in that amount of time.

    Make sure you're drawing and returning water only to the spa. Otherwise, there's something wrong with that heater. Figure an 800 gallon spa holds roughly 6400 pounds of water. It takes 6400 BTUs to heat it one degree. 400,000/6400 = 62.5 degrees per hour in a perfect world. You'll lose a lot of heat to the underground plumbing and the plaster and to surface losses, but in forty minutes you should see way more than 4 degrees rise.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Time to heat up spa

    The H400 is about 82% efficient. Therefore, only about 328,000 btu per hour actually get in the water. A 655 gallon spa should gain about 1 degree per minute not accounting for any heat loss from the water.

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    Re: Time to heat up spa

    Thanks all! I will check to see if it's heating the pool as well. It certainly shouldn't be, but I'll check. It is different pumps for the pool and spa.

    The heater seems to be working fine. The vent is blowing some awfully hot air.


    Oh and sorry for the double post!
    Approx 25k gallon PebbleTec in-ground diving pool and attached raised (10 person?) spa, with spillover and waterfall.
    Hayward AquaLogic PS-4 control board, Hayward SP3400VSP Ecostar pump, Hayward C5520CP cartridge filter, Hayward H400FDN 400k BTU NG heater

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    Re: Time to heat up spa

    Okay, so I'm at the house now. It's not feeding the pool. The flow at the spa jets seems normal. The heater cycles on and off.

    Here's the odd part. The release valve at the water outlet of the heater isn't releasing very hot water at all. It's lucky to be warm even. Why could that be???

    The blower is blowing VERY hot air from the vent on top, so I know the exchanger is getting hot.

    Please help!
    Approx 25k gallon PebbleTec in-ground diving pool and attached raised (10 person?) spa, with spillover and waterfall.
    Hayward AquaLogic PS-4 control board, Hayward SP3400VSP Ecostar pump, Hayward C5520CP cartridge filter, Hayward H400FDN 400k BTU NG heater

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    Re: Time to heat up spa

    The cycling indicates a problem. Can you post a picture of the system?

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    Re: Time to heat up spa

    Here you go. I know, it's a mess there. I literally just closed on the house Friday, so I haven't cleaned yet.

    THANK YOU for your help.









    Approx 25k gallon PebbleTec in-ground diving pool and attached raised (10 person?) spa, with spillover and waterfall.
    Hayward AquaLogic PS-4 control board, Hayward SP3400VSP Ecostar pump, Hayward C5520CP cartridge filter, Hayward H400FDN 400k BTU NG heater

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    Re: Time to heat up spa

    As stated above, the water coming out that release valve on the heater is far from hot. That should be the return line, so I'd expect it to be downright hot at that valve. The heater is firing up, and as stated air out the vent is darn hot.

    Is there some sort of emergency bypass inside the heater in case there's a blockage? That's the only reason I can fathom those symptoms.

    Thanks again for your help...
    Approx 25k gallon PebbleTec in-ground diving pool and attached raised (10 person?) spa, with spillover and waterfall.
    Hayward AquaLogic PS-4 control board, Hayward SP3400VSP Ecostar pump, Hayward C5520CP cartridge filter, Hayward H400FDN 400k BTU NG heater

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    Re: Time to heat up spa

    I'm guessing that could be the culprit right there? The diverter valve?

    If water wasn't flowing properly, that would in and of itself cause the heater to cycle, right?

    Approx 25k gallon PebbleTec in-ground diving pool and attached raised (10 person?) spa, with spillover and waterfall.
    Hayward AquaLogic PS-4 control board, Hayward SP3400VSP Ecostar pump, Hayward C5520CP cartridge filter, Hayward H400FDN 400k BTU NG heater

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    Re: Time to heat up spa

    That valve is just a safety relief. You have a pool spa combo with the same system for both. The extra pump is probably just for the jets. I think that your valves are misconfigured.

    You want to isolate the spa so that you're only pulling water from the spa and returning water to the spa.

    The exhaust is hot due to the 72,000 btu per hour lost as waste heat. The return water should not be getting hot if the flow is correct. With proper water flow, the return water should only gain a few degrees and will be warmer than the incomming water, but not hot.

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    Re: Time to heat up spa

    Quote Originally Posted by JamesW View Post
    ...You want to isolate the spa so that you're only pulling water from the spa and returning water to the spa...
    I'm pretty sure that the spa is isolated and pool water is not included in the mix. The skimmer in the pool shows no activity, and all the jets seem to be calm in the pool.
    Approx 25k gallon PebbleTec in-ground diving pool and attached raised (10 person?) spa, with spillover and waterfall.
    Hayward AquaLogic PS-4 control board, Hayward SP3400VSP Ecostar pump, Hayward C5520CP cartridge filter, Hayward H400FDN 400k BTU NG heater

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    Re: Time to heat up spa

    The valves do not look right. You're going to have to figure out what each pipe goes to and how every valve works to make sure that the flow is correct.

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    Re: Time to heat up spa

    I am guessing, seeing a handle is broke, one or more of the three way valves is not working properly. Shut everything down and pop the bodies out to verify.

    - - - Updated - - -

    Or go to home depot and buy regular ball valves to replace them....

  16. Back To Top    #16

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    Re: Time to heat up spa

    Thanks! That wouldn't explain the cycling of the heater though, correct?
    Approx 25k gallon PebbleTec in-ground diving pool and attached raised (10 person?) spa, with spillover and waterfall.
    Hayward AquaLogic PS-4 control board, Hayward SP3400VSP Ecostar pump, Hayward C5520CP cartridge filter, Hayward H400FDN 400k BTU NG heater

  17. Back To Top    #17

    Re: Time to heat up spa

    The valves are set incorrectly. The three way with the broken handle should be turned 180 degrees so that the center arrow is pointing to the right. The center arrow points to the closed line (look closely and you will see the word "closed" in front of the arrow. You're blocking almost all of the flow. I would suspect that the filter pressure is almost maxed out.

  18. Back To Top    #18

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    Re: Time to heat up spa

    Changing that valve seems to do nothing. The pressure really doesn't change regardless of where it's set. The pressure gauge appears to be working fine.

    I put a call in to two pool guys. Neither has gotten back to me yet. Very frustrating.
    Approx 25k gallon PebbleTec in-ground diving pool and attached raised (10 person?) spa, with spillover and waterfall.
    Hayward AquaLogic PS-4 control board, Hayward SP3400VSP Ecostar pump, Hayward C5520CP cartridge filter, Hayward H400FDN 400k BTU NG heater

  19. Back To Top    #19

    Re: Time to heat up spa

    What is the filter pressure?

    Is that a cartridge or de filter?

    Does the gauge go to zero when the pump is off?

    What is the rightmost pipe on the return manifold?

    Can you identify the pipes on the suction manifold from left to right?

  20. Back To Top    #20

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    Re: Time to heat up spa

    Quote Originally Posted by JamesW View Post
    What is the filter pressure?

    Is that a cartridge or de filter?

    Does the gauge go to zero when the pump is off?

    What is the rightmost pipe on the return manifold?

    Can you identify the pipes on the suction manifold from left to right?
    Thanks for your help, James!

    Pressure is around 22 lbs. It's a cartridge filter, I believe. The gauge does drop to zero when the pumps are turned off.

    I'm not at the house now, so can't say which are which, and not all are even labeled. I can check tomorrow and reply as best I can.

    Can you clarify what you mean by suction manifold and return manifold?

    Thank you again!
    Approx 25k gallon PebbleTec in-ground diving pool and attached raised (10 person?) spa, with spillover and waterfall.
    Hayward AquaLogic PS-4 control board, Hayward SP3400VSP Ecostar pump, Hayward C5520CP cartridge filter, Hayward H400FDN 400k BTU NG heater

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