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Thread: Testing Pump Flow -vs- Heater Flow Switch

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    Testing Pump Flow -vs- Heater Flow Switch

    My heater is not turning on because the pressure switch is apparently not being triggered (seeing the "FLO" message perpetually).

    I'm trying to isolate whether it is:
    (a) bad flow switch (or)
    (b) pump volume has gone down for some reason

    Hardware involved:
    * AquaCal TT120 Heat Pump (internal pressure switch should trigger at roughly 30 GPM)
    * WhisperFlo WFE-3 (3/4 HP Impeller) Recirculation Pump
    Running B891 Motor @ Full Speed, 1.2 SHP (0.75 * 1.65)
    * Approx 40' of 2" Pipe from Pool to Recirculation Pump, 5 elbows.
    * Hayward 24 SqFt DE Filter (take out of the equation by setting valve to skip filter)

    The back story:
    * The recirculation pump was sucking some air ... around the same time, I noticed the heater was not coming on.
    * I serviced the pump (normal go-kit full gasket replacement), double-checking impeller vanes.
    * Re-assembled everything and pump seems to be running good (no more air getting in).

    However, the heater is still reading "FLO" signalling that the pressure switch isn't being triggered.

    I eliminated the heater by setting the Hayward multi-valve to skip the filter.

    I then tried backwashing and it did seem the pump was slower than it was previously (but I didn't feel it was exceptionally slow).

    As water is passing through the line, I looked at the Jandy Check Valve (the 2/2.5" Jandy black valve) and noticed that the check-valve-flap is only opening to about 15 degrees, as opposed to about 80 degrees (nearly full-open) when running a high-volume pump.

    On one hand, I'm leaning towards the thought that the pump may not be pumping enough volume because it does seem to be lower than it had been.

    On the other hand, the persistent FLO arose before I switched out the pump and it could be the flow switch is bad.

    ...At this point I'm out of ideas and to move forward, I thought I'd seek the advice of TFP members...

    Is there a way that I can isolate whether it's the (a) heater's flow switch or the (b) the pump's volume being too low? For example, an easy way to determine the GPM the pump is putting out?

    Separate question .. If it turns out it is the flow switch, or the diagnostic is more than I am able to do with TFP help, does anyone know of a very good pool plumber in the West Palm Beach, FL area?

    Thank you in advance for any ideas or suggestions
    15,000 gal/16x32 Doughboy expandable vinyl liner pool, w/deep end
    Hayward Pro Series high rate sand filter/Powerflow Matrix 1.5 hp pump

  2. Back To Top    #2

    Join Date
    Oct 2013
    Jupiter, FL

    Re: Testing Pump Flow -vs- Heater Flow Switch

    If it turns out to be something with heater, AquaCal has local technicians (employees of AquaCal) that can come help diagnose problems. I had the compressor replaced earlier in the year, and the guy was prompt and professional (I believe he was dispatched out of Boca). The service call was $80 (I think) which was applied to the repair bill even though he had to come back a week later with the part. The part itself was also under warranty, which saved money.

    I've seen the similar "FLO" message a couple times, but it's always cleared up by simply washing out the filter. Hopefully you can get it cleared up with as simple a fix -- it's cold out there this morning

    Sorry I couldn't be more help. Hopefully the experts can chime and be of more assistance.
    18'x9', IG, Plaster, AutoPilot Pool Pilot Digital Nano SWG (RC-35/22 Cell), 1 HP Sta-Rite Dyna-Glas Pump, Sta-Rite PXC75 Posi-Clear Cartridge System, AquaCal Heatwave Heat Pump.

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    mas985's Avatar
    Join Date
    May 2007
    Pleasanton, CA

    Re: Testing Pump Flow -vs- Heater Flow Switch

    The pressure switch works on pressure not flow rate. What is the filter pressure and is it higher or lower than normal?

    Symptom sound like a suction side blockage so I would expect the filter pressure to be lower than normal.
    Hydraulics 101; Pump Ed 101; Pump and Pool Spreadsheets; Pump Run Time Study; DIY Acid Dosing; DIY Cover Roller
    18'x36' 20k plaster, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge, Solar, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater, ThePoolCleaner

  4. Back To Top    #4

    Re: Testing Pump Flow -vs- Heater Flow Switch

    Using negative and positive pressure gauges, directly before and after the pump will give you total ft. of head, which can be used when referencing a mfg. pump submittal sheet gpm chart.
    1 ft = 0.433 psi, or 2.31 ft = 1 psi
    24k gallon inground vinyl liner pool, 8'-3' depth, 2 skimmers, 3 returns, basic 5 chem kit.
    Hayward: DE-60 filter, Superpump VS, AquaRite salt chlorinator w/T-Cell 15, TigerShark QC robot. Jacuzzi hot tub ~350gal. Air blower type, w/8 jets.

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