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Thread: Heat Pump will not turn on when pump is on low speed

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    Heat Pump will not turn on when pump is on low speed

    The heat pump will not turn on when it is on low speed. Apparently, there is not enough flow. My goal was to run the pump on low speed for 24 hours or less to turn the water, and high speed when running the sheer descents or The Pool Cleaner.

    The pump is a Hayward Tristar Dual Speed pump 1.5 HP.

    We would like to keep the pool around 88 degrees and minimize the electric bill.

    Did I buy the right Hayward pump? Should I have bought the Hayward 1HP super pump?

    Will I still save money on the electric bill by running the pump on high for around 4-6 hours a day and running on low for around 12-14 hours a day compared to running a Hayward 1Hp super pump on high for 12 hours a day?

    What time intervals and how many hours on each speed would you recommend to keep the water turning and pool heated to around 88 degrees?

    Any advice is greatly appreciated.
    18 x 36 vinyl IG- 3.5 to 5 ft.- 20,000 gallaons, TF-100 Test Kit, Hayward TriStar Dual Speed 1.5 HP pump, Hayward C3025 SwimClear Cartridge Filter, Hayward SWG, Hayward Heat Pump 21104T, 2 inch PVC, 3 returns, 2 skimmers, 2 Low Suction (no main drain), Dedicated Suction for The Pool Cleaner 4x, Prologic 8 with Aquapod, 2 Colorlogic LED lights, (2) 16 inch sheer descents

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    Mod Squad Bama Rambler's Avatar
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    Re: Heate Pump will not turn on when pump is on low speed

    What's your filter pressure when on low speed?
    What size are your eyeball(s) and how many are there?
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: Heate Pump will not turn on when pump is on low speed

    What's probably happening is that, the pump isn't producing enough pressure to trip the pressure sensor in the heat pump. The sensitivity of the switch can be raised or lowered, but it should only be done by a pro.

    I'll let others provide more on this, yet still be here to answer your questions





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    Re: Heate Pump will not turn on when pump is on low speed

    The pressure on the filter is 4 psi when on low speed.

    There are 3 returns and they are 3/4 of an inch.
    18 x 36 vinyl IG- 3.5 to 5 ft.- 20,000 gallaons, TF-100 Test Kit, Hayward TriStar Dual Speed 1.5 HP pump, Hayward C3025 SwimClear Cartridge Filter, Hayward SWG, Hayward Heat Pump 21104T, 2 inch PVC, 3 returns, 2 skimmers, 2 Low Suction (no main drain), Dedicated Suction for The Pool Cleaner 4x, Prologic 8 with Aquapod, 2 Colorlogic LED lights, (2) 16 inch sheer descents

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    Re: Heate Pump will not turn on when pump is on low speed

    most heater pressure switches wont allow them to fire with a 2 speed pump on low. This is why a VS pump is so nice....

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    Re: Heat Pump will not turn on when pump is on low speed

    This is a brand new pump and pool.

    What should I do?
    18 x 36 vinyl IG- 3.5 to 5 ft.- 20,000 gallaons, TF-100 Test Kit, Hayward TriStar Dual Speed 1.5 HP pump, Hayward C3025 SwimClear Cartridge Filter, Hayward SWG, Hayward Heat Pump 21104T, 2 inch PVC, 3 returns, 2 skimmers, 2 Low Suction (no main drain), Dedicated Suction for The Pool Cleaner 4x, Prologic 8 with Aquapod, 2 Colorlogic LED lights, (2) 16 inch sheer descents

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    Mod Squad Bama Rambler's Avatar
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    Re: Heate Pump will not turn on when pump is on low speed

    The easiest thing to do is change the eyeballs to ½" and see if that raises your pressure enough to allow the HP to run. Also clean your filter if you haven't done that in a while.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
    Pool School ----- Pool Math ----- TF-Test Kit

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    Re: Heat Pump will not turn on when pump is on low speed

    Thanks Bama Rambler. I will change the eyeballs to 1/2 inch. The filter is new, but I will check to see if it needs cleaning.
    18 x 36 vinyl IG- 3.5 to 5 ft.- 20,000 gallaons, TF-100 Test Kit, Hayward TriStar Dual Speed 1.5 HP pump, Hayward C3025 SwimClear Cartridge Filter, Hayward SWG, Hayward Heat Pump 21104T, 2 inch PVC, 3 returns, 2 skimmers, 2 Low Suction (no main drain), Dedicated Suction for The Pool Cleaner 4x, Prologic 8 with Aquapod, 2 Colorlogic LED lights, (2) 16 inch sheer descents

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    Re: Heat Pump will not turn on when pump is on low speed

    Another option is to find a flow switch that senses flow above the minimum for your heater. Install the flow switch in place of the pressure switch.

    Note: If this is not done correctly, then the heater can be damaged.

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    no-mas's Avatar
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    Re: Heat Pump will not turn on when pump is on low speed

    Sounds really similar to my setup, except I have plenty of flow to run my heat pump on low. Usually when on low, I have one, maybe 2 psi. Assuming the cartridge is clean, perhaps there is an external bypass on the heat pump that you can close? How about a picture of the pad?
    18k gal inground, everbrite finish, 505 sq ft; 1.5 hp two speed whisperflow; rheem 5100ti 100k btu heat pump; 3 sheer descent falls; DE filter; swg (cell out and using trichlor for now)

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    Re: Heat Pump will not turn on when pump is on low speed

    I would ask the person who sold me the heater and pump together knowing that the heater couldn't be utilized on low. A VS pump is prob the best option to use the heater without a high speed. This same thing happens with SWG.

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    no-mas's Avatar
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    Re: Heat Pump will not turn on when pump is on low speed

    anything new, ohiorooie?
    18k gal inground, everbrite finish, 505 sq ft; 1.5 hp two speed whisperflow; rheem 5100ti 100k btu heat pump; 3 sheer descent falls; DE filter; swg (cell out and using trichlor for now)

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