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Thread: RPM Setting for maximum heat rise

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    justinfrancisjudd's Avatar
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    Dec 2014
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    RPM Setting for maximum heat rise

    Hey everyone,

    Quick question that may be a dumb one. When heating your spa is there an ideal rpm setting for maximum heat rise with minimal time running the heater?

    I have a Jandy LXI 400KBTU heater and Jandy 2.0hp vs EPump. My pool builder set the default speed to 2250RPMs' when the spa is heating, it seems to jump up to full jet speeds at 3450rpms some of the time when i put it to spa mode and heat on, sometimes i override it to the 2250 sometimes i let it run full speed. The manual calls for 75gpm flow through the heater for ideal working flow while heating. I can't find anywhere where i could figure with my pump running what speed will give me that ideal heating flow rate. obviously the lower speed setting uses less energy and the slower flow I would think would allow the water to heat better as it passes through the equipment.


    Right now its taking about 30 mins to go from the high 70s to 104, and and hour to 104 if the pool is colder high 60s/low70s.


    Any ideas of the ideal setting from anyone with an epump or similar variabel speed pump

    Thanks,

    Justin
    2015 Build, Stonescapes Mini Pebble-Blue Sea, 46.5'x23', 9' deep, Paramount IFCS on steps and shelfs, 8' spa with spillover, Quartzite Flagstone Coping and Patio, 3" Suctions and Returns, 1 skimmer, 6 Jandy LED Watercolor lights, Baja Shelf w/ diving rock, 2x 2HP Jandy VS E-Pump, Jandy LXI 400K BTU Heater Cupro/Nickel exchanger, Cartridge Filter, Grotto/Waterfall/ Slide, Jandy SWG, I-aqualink 2.0

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    mas985's Avatar
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    May 2007
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    Re: RPM Setting for maximum heat rise

    Just the opposite. Faster flow rate is more efficient because it minimizes the heat gain in the plumbing which is a source of heat loss. Lower flows heat the water in the pipes to a higher temperature with the same BTU gain but higher water temperatures in the pipes result in more heat loss. But it probably isn't much to get excited about.
    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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    justinfrancisjudd's Avatar
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    Re: RPM Setting for maximum heat rise

    Quote Originally Posted by mas985 View Post
    Just the opposite. Faster flow rate is more efficient because it minimizes the heat gain in the plumbing which is a source of heat loss. Lower flows heat the water in the pipes to a higher temperature with the same BTU gain but higher water temperatures in the pipes result in more heat loss. But it probably isn't much to get excited about.
    Thanks! What are you all typically running your rpms while heating?

    The other side was my old meter was only a 240k btu unit. they just did the big 630 btu residential btu gas meter finally so maybe that will make things more efficient
    2015 Build, Stonescapes Mini Pebble-Blue Sea, 46.5'x23', 9' deep, Paramount IFCS on steps and shelfs, 8' spa with spillover, Quartzite Flagstone Coping and Patio, 3" Suctions and Returns, 1 skimmer, 6 Jandy LED Watercolor lights, Baja Shelf w/ diving rock, 2x 2HP Jandy VS E-Pump, Jandy LXI 400K BTU Heater Cupro/Nickel exchanger, Cartridge Filter, Grotto/Waterfall/ Slide, Jandy SWG, I-aqualink 2.0

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    mas985's Avatar
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    May 2007
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    Re: RPM Setting for maximum heat rise

    Normally, I heat the spa (gas heater) and pool (solar heater) on high speed.
    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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