Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 9 of 9

Thread: System Pressure Anomaly

  1. Back To Top    #1

    Join Date
    Jul 2014
    Location
    Hopkinton, MA
    Posts
    28

    System Pressure Anomaly

    I have some odd behavior that I can't explain, so I thought I would post here looking for an explanation.

    I recently replaced the A.O. Smith 1.5 HP 2 speed motor on my Hayward Superpump with the variable speed Ecotech EVSJ3-NS. The two speed motor was getting really loud and the low speed setting was not getting enough flow through my piping for the SWG to work properly.

    When I replaced the motor, I found the impeller had a bit of pine needle crud clogging it in a few places, so I cleaned it out. (That may have been contributing to the low flow on the old motor on low). The new motor is now working great- I can set it at 55% to keep the SWG happy and bump it up to 75% when the Polaris is running. What is confusing me is the pressure readings. With the old 1.5HP pump on high and a freshly backwashed filter I would get about 16 PSI on my gauge. With the new 3HP pump at 100% the pressure on the gauge is only at 12 PSI. How can the pressure be lower with the new pump when it should be turning the impeller as fast as the old pump? Could the crud in the impeller with the old pump have impacted laminar flow and resulted in a higher pressure? Could air have been collecting in the filter with the reduced flow of the old pump/cruddy impeller and increasing the pressure reading?
    ~26K Gallon, Gunnite IG, Hayward S270T Sand Filter, Hayward Super Pump w/ Ecotech EVSJ3 VS Motor
    Circupool RJ45 SWG, Dolphin S200 robotic cleaner, Rheem 400K BTU Propane Heater, 80sqft solar heater array

  2. Back To Top    #2

    RonsPlc's Avatar
    Join Date
    May 2015
    Location
    Gaylesville, AL
    Posts
    360

    Re: System Pressure Anomaly

    I may be wrong here, but I think you are reasoning that ... higher HP=higher flow ... What you should be looking at rather is the GPH, or GPM that the pumps have. (Gallons Per Hour, Gallons Per Minute)

    A 1.5hp with 3600GPH is going to show higher on you gauge than the same HP, or higher that only has 3000GPH.
    14600 gal Intex 24' Round 52" deep AG Pool (Heavily Modified)
    200lb sand filter w/2 speed 1.5/0.5hp pump
    Stenner 45MHP10 Liquid Chlorine (well... bleach) Injector. Borates added.
    K-2006 test kit w/Speedstir
    Pool School - PoolMath - HIGHLY Recommended Test Kits

  3. Back To Top    #3

    Join Date
    Jul 2014
    Location
    Hopkinton, MA
    Posts
    28

    Re: System Pressure Anomaly

    Since the impeller and pump stayed the same between the two, I'm assuming that at max speed both motors are turning the impeller at 3450 RPM which should create an equal GPH between the two, provided the 1.5HP motor had enough umph to achieve 3450 RPM. With an equal GPH I would expect equal pressure readings. Further, I would expect the cruddy impeller to decrease GPH and hence decrease the pressure reading, but I am seeing the opposite. I guess one other variable is the sand in the filter. Is it possible it has gotten channels in it over a period of 2 weeks that decrease the pressure?
    ~26K Gallon, Gunnite IG, Hayward S270T Sand Filter, Hayward Super Pump w/ Ecotech EVSJ3 VS Motor
    Circupool RJ45 SWG, Dolphin S200 robotic cleaner, Rheem 400K BTU Propane Heater, 80sqft solar heater array

  4. Back To Top    #4
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    11,482

    Re: System Pressure Anomaly

    All that is true but are you sure you are running at 3450 RPM?

    Also, are all the valve settings the same and did you clean the filter when you changed the motor?
    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

  5. Back To Top    #5

    Join Date
    Jul 2014
    Location
    Hopkinton, MA
    Posts
    28

    Re: System Pressure Anomaly

    I don't really know that I am running at 3450 RPM, just that the pump is set to 100% and that is its spec'd RPM. The flow looks to be greater than what the old motor did on high (as measured by eye-balling the flow through the clear part of the SWG). I didn't do a thorough cleaning of the filter when I changed the motor, but I did a backwash a few days after the change. Valve settings are all the same for comparison purposes.
    ~26K Gallon, Gunnite IG, Hayward S270T Sand Filter, Hayward Super Pump w/ Ecotech EVSJ3 VS Motor
    Circupool RJ45 SWG, Dolphin S200 robotic cleaner, Rheem 400K BTU Propane Heater, 80sqft solar heater array

  6. Back To Top    #6
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    11,482

    Re: System Pressure Anomaly

    So was the pressure reading after the backwash? That could explain it.
    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

  7. Back To Top    #7

    Join Date
    Jul 2014
    Location
    Hopkinton, MA
    Posts
    28

    Re: System Pressure Anomaly

    The 12 PSI on the new motor was after the backwash, but with the old motor it would only drop to 16 PSI after a backwash. I wonder if doing the backwash with the impeller cleaned up might have done a better job and resulted in the lower pressure afterwards.
    ~26K Gallon, Gunnite IG, Hayward S270T Sand Filter, Hayward Super Pump w/ Ecotech EVSJ3 VS Motor
    Circupool RJ45 SWG, Dolphin S200 robotic cleaner, Rheem 400K BTU Propane Heater, 80sqft solar heater array

  8. Back To Top    #8
    mas985's Avatar
    Join Date
    May 2007
    Location
    Pleasanton, CA
    Posts
    11,482

    Re: System Pressure Anomaly

    Yes, a clean impeller would do a much better job removing debris from the filter.
    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

  9. Back To Top    #9

    Join Date
    Jul 2014
    Location
    Hopkinton, MA
    Posts
    28

    Re: System Pressure Anomaly

    Thanks. I can accept that as a plausible explanation
    ~26K Gallon, Gunnite IG, Hayward S270T Sand Filter, Hayward Super Pump w/ Ecotech EVSJ3 VS Motor
    Circupool RJ45 SWG, Dolphin S200 robotic cleaner, Rheem 400K BTU Propane Heater, 80sqft solar heater array

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •