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Thread: Heating pool

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    Join Date
    Mar 2011
    Location
    Houston, TX
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    70

    Heating pool

    My daughter is having a birthday party on March 2nd and wants to heat the pool. I am trying to figure out how long I will need to heat it to get to temperature. I am thinking a water temp of 85 should be warm enough for kids. I am located in Houston, TX so there is no telling what the weather will be like in early March. Could be 90 outside or 40. Currently our water temp is 61 degrees. Pool is roughly 18,500 gallons and my heater is a Jandy LT400N-L and is rated at 399,000 btu / hr. Is there a formula for me to determine how long it will take to heat my water?
    18,500 gallons, Cartridge Filter, In Ground Plaster. Jandy CL460 Filter

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    Join Date
    Aug 2011
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    Metro Atlanta, Georgia
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    Re: Heating pool

    It takes 1 BTU to heat 1 pound of water 1 degree, you have 18500 gallons of water at 8.35 lbs per gallon (154475 lbs). So your heater will heat the pool 2.58 degrees an hour, assuming 100% effeciency. Or, about 7.75 hours to raise the pool 20 degrees, but I would assume a lower effeciency. Since my memory might not have this completely, correct, maybe someone will drop by and give you a more accurate calc, if necessary.
    My cement pond is a 36K gunite 20X40 built in mid 1960s, Hayward S244S filter, Aquarite SWCG, Jandy 1.5HP 2sp, TF-Test kit and Nitro Wall Climber

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    Join Date
    Dec 2009
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    Central Massachusetts
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    Re: Heating pool

    Thats pretty close. I got 9 hours for a 24 degree rise.

    18,500 x 8.33 = 154105 x 24=3698520/ 400, 000= 9.2 hours.

    Assuming the heater is 85% efficient, it will take roughly 11 hours. At 4 therms per hour, thats 36 therms at ~$1.00 per therm, (unless your gas prices are pretty high), thats about $35-40 to heat it up. Not bad really.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    smccull's Avatar
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    Apr 2010
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    Allen, TX
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    Heating pool

    1 BTU = energy to heat 1 lb water by 1 degree F. Assume 90% efficiency for heater, then your 400,000 BTU heater can heat 360,000 lbs of water by 1 degree per hour. 18,500 gal pool x 8.34 lbs per gallon for water = 154000 lbs water. So I would estimate around 2 degrees per hour ignoring any solar gain or heat loss from wind.

    A solar blanket/cover would be highly recommended.

    Depending on how your gas is priced (either therms or Mcf) - around 1000 BTU per cubic foot or gas. 100 cf in a therm and 1000 cf in Mcf. Gas in Dallas is around 4.50 per Mcf - 400,000 BTU heater burns 400 cf per hour or .4 Mcf so around 2 bucks per our or a dollar per degree!


    ---
    I am here: http://maps.google.com/maps?ll=33.087743,-96.648886
    Steve
    Deep in the Heart......errrr HEAT of Texas
    20k gallon gunite formal

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    smccull's Avatar
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    Apr 2010
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    Allen, TX
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    Heating pool

    I guess we were all typing at the same time!


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    I am here: http://maps.google.com/maps?ll=33.087672,-96.648863
    Steve
    Deep in the Heart......errrr HEAT of Texas
    20k gallon gunite formal

  6. Back To Top    #6

    Join Date
    Jan 2011
    Location
    Richmond, Texas
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    594

    Re: Heating pool

    @brownchristian - It will depend on the weather. I live SW of Houston and I can tell you to just to heat my 10+K pool it is about 40 bucks on average. However the real factor will be the weather and wind. Hot and humid and no wind it will be easy to heat up. Cool and windy it will take a long time. I can heat my pool about 4 degrees per hour until I get close to the outside temp after that it takes a long time.
    Approx 11K Gal. 10'X30' Semi free-form IG - 6 ' raised spa w/6 jets - 10' circle sun shelf with 1 bubbler - Waterfall - 3 / 1.5 HP pumps - Polaris 280 Cleaner - 3 Pentair Color LED Intellibrite Lights - Pentair 400K Master Temp - 2 Valve Actuators - 5 Fiberstar Mini Laminars - 1 Fiberstars 2004 Illuminator - 2 Skimmers - 6 Returns - Caribbean Blue Pebble Tech - 600+ sq ft kool decK - Auto Fill - 2 Boston Acoustics VOYA RK5 Outdoor Rock Speakers - 2 TIC Corporation TFS5CN 6.5-Inch 150-Watt Terra-Forms Rock Speakers - Apple Airport Express - 1 Awesome View.

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    Lershac's Avatar
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    May 2007
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    Baton Rouge, LA
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    1,215

    Re: Heating pool

    One tip... heat the water to temp a day early, cover it if you have one, and check your chemicals a couple of times after it heats up. Thing change when you pump that much heat in.
    (DIY):16K Gal 20X30 rectangular IG Gunite, w/spa, CCP 520 filter,2 Pentair VS pumps, 400KBTU Pentair gas heater, Heat Pump for cooling, **update5.25.2013** added an intellichem with acid pump that will control existing SWG. My Build Thread Here

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