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Thread: Pump Speed While Heating

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    cnr1089's Avatar
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    Aug 2010
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    Southern NH
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    Pump Speed While Heating

    First season with a pool (well, it finished at the VERY end of last season, we didn't have time to use the heater other then to make sure it works).

    I have both a Propane heater and a heat pump. It has been pretty cold around here, but it will be 70 at least 3 days this week (and the kids are off from school), so we are itching to use the pool. Right now the water fluctuates between 47 and 55 degrees (night to day).

    Anyways, time to try out our heater and make the pool usable this week (need to cut our solar core to fit our pool, hope to do that tomorrow when things dry out).

    I have a mutli-speed pump. Is the heater as efficient when the pump is running low speed? I would figure since the water flows through the heater slower, then it would have more time to heat up and it would not make things less efficient.

    What is the thought? Especially since we will probably be running the heater (propane for now) for about 24 hours in a row to get the pool up to swimmable temperatures.
    26k gal IG, Gunite Baha Sand River Rok (pebble), Hayward DE6020 Filter (120GPM), Hayward NorthStar 2HP (dual speed) pump, Hayward H400FDP 400kBTU heater, Aqua Comfort Heat pump, Pro Logic Automation and Chlorination (SWG), Polaris 3900 (we call him Fred, he likes to get stuck in the corner of our stairs). Watch our pool being built http://www.youtube.com/watch?v=S61tQm2fp08

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    JasonLion's Avatar
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    May 2007
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    Silver Spring, MD
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    Re: Pump Speed While Heating

    With a 400k BTU heater you need a fairly good flow rate to keep the heater working well, probably 40 GPM or more. I'm not sure if your pump moves that much water on low speed or not. It would depend on many details of your plumbing.
    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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    mas985's Avatar
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    May 2007
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    Pleasanton, CA
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    Re: Pump Speed While Heating

    Quote Originally Posted by cnr1089
    I have a mutli-speed pump. Is the heater as efficient when the pump is running low speed? I would figure since the water flows through the heater slower, then it would have more time to heat up and it would not make things less efficient.
    Heat loss is dependent on the temperature differences so the hotter the water, the faster the heat will be lost so lower flow rates result in poorer efficiency. Not much different than a solar heater. Plus, the hotter water is in the pipes longer at lower flow rates so more time to lose head so again, the efficiency will drop some.
    Mark
    Hydraulics 101; Pump Ed 101; Pump/Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, MaxFlo SP2303VSP, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater

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