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Thread: heat at low flow rate & pressure switches

  1. Back To Top    #1

    Join Date
    Dec 2013
    SF, CA, USA

    heat at low flow rate & pressure switches

    hi folks! for my tub, near the master bedroom, i'm hoping to keep pump noise way down by using a low flow rate, maybe even lower than the exorbitant variable-speed pumps will go. i calculated that 5 gpm at 30KBTU/hr would give me a nice temperature rise in the 5 gallons of 12.5 degrees F. the ray-pak heater has a pressure switch 062237B, which if i am reading the manual correctly, seems like putting a 20 GPM floor on the flow rate. the manual even says hi-lo pumps may have to run in high to turn the heat on. how can i heat the tub with such a slow flow and not give up the safety of the pressure switch? perhaps there is another kind of more sensitive pressure switch i can install?
    plumbing up wall-mounted equipment and plenty gauges below a 500G wooden outdoor hot tub.

  2. Back To Top    #2
    Mod Squad JohnT's Avatar
    Join Date
    Apr 2007
    SW Indiana

    Re: heat at low flow rate & pressure switches

    Heaters aren't very efficient at low flow rates, so you need to be careful slowing the pump down every much.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

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