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Thread: Power consumption of 2 spd pump measured with and w/o solar

  1. Back To Top    #1

    Join Date
    Jun 2007
    Location
    Hunterdon County New Jersey
    Posts
    19

    Power consumption of 2 spd pump measured with and w/o solar

    There seems to be a lot of talk these days about saving electricity. And rightly so! Electric rates have gone way up, and people are starting to feel it in their checkbooks! I thought this to be appropriate for the "deep-end". (Even though I don't have one ) I have learned so much here at TFP, I thought I would share some of my experiments.

    My recently completed AGP is 15x30 (12,000 gal) and I am using a Tagelus TA-60D (300lb) sand filter with a 2-speed Waterway Supreme HI-FLO pump 3/4 HP. Also installed are 2 Fafco "Solar Bear" panels each 4x20 plumbed using PVC. I can switch the solar on and off using a 3 way valve. The 2 panels are currently plumbed in series only because I didn't have all the PVC fittings I needed. I will make the change to parallel flow soon to increase GPM flow.

    The pump data-plate specs are:
    Model #: PSP2075-6R
    Volts: 115
    RPM: 3450/1725
    Amps: 8.8 (Hi) and 2.6 (low) which calculates to 1012 watts (hi spd) and 299 watts low speed.

    Using a Kill-A-Watt meter, I was able to determine that my pump uses significantly less power than its data-plate suggests :P

    Hi-speed without solar (less head; higher flow): 745 watts
    Hi-speed with solar (more head; lower flow): 662 watts
    Low-speed without solar: 138 watts
    Low-speed with solar: 127 watts

    Let's calculate how much this will cost per month if the pump is run 10 hours per day on low speed with the solar turned on:
    Cost per KwH: $0.185
    KwH per day: 1.27 (127 watts div 1000 * 10 hours/day)
    Days per month: 30

    Cost to run pump on low speed per month: $7.05

    Initial flow rate measurements seem to indicate I am only getting about 15 GPM. Hopefully this will increase when I switch the solar to parallel flow. But even this seems sufficient to keep my pool clean and warm.

    Of course this does not take into consideration electric-motor startup surge, or running the pump on high-speed for cleaning or back washing, but I expect this to be a rather small cost.

    I attached the pumps head/flow graph.

    So the whole point of this is you can save significant money by running a 2 speed pump. I still need to do more precise flow rate measurements. Hopefully I can have those for the forum soon.

    Jason M
    Attached Images Attached Images
    15x30 AGP built myself in 2008: 3/4 hp 2-speed Waterway Supreme. 300 lb Pentair sand filter. 160 SqFT solar.

  2. Back To Top    #2

    Join Date
    Jun 2007
    Location
    SF Bay Area
    Posts
    441
    Jason,

    Great post!

    I have a Kill-A-Watt meter also, but I can't use it to measure my pool pump electrical usage since it is 240 Volt.

    Using a Kill-A-Watt meter, I was able to determine that my pump uses significantly less power than its data-plate suggests
    This is not too surprising. The motor HP rating is how much HP the motor can supply to the pump without overheating. The actual HP load is determined by the characteristics of the pump itself (impeller, head, etc.) So the pump "demands" a certain level of HP and the motor supplies that amount of demanded HP. In fact, your motor would probably supply a much greater amount of HP that its nameplate HP - perhaps as much as 1 1/2 or 2 HP. It is just that the motor will overheat at anything over 3/4 HP (or maybe a little more if the motor SF is over 1.0).

    Of course this does not take into consideration electric-motor startup surge
    While it is true that an electric motor will use 6-8 times normal electrical current on startup, it is also true that this startup time is only a fraction of a second. Except for very limited and special cases in industrial facilities, the "startup surge" of an electrical motor does not cost a homeowner even a fraction of a cent.

    Thanks again for your great post. Can we see pictures? (We love pictures !!)

    Titanium
    24,000 gallon inground freeform pool/spa circa 1983 (113 ft perimeter, 625 sq ft) with 350 gallon attached spill-over spa
    2007 2 HP, three-phase Hayward TriStar pump which is powered by an Ikeric VS-200 variable speed drive system
    1983 Laars XE Pool/Spa Heater Type ES 400,000 BTU, 1998 Hayward Super Star-Clear C-4000 cartridge filter (400 sq ft, 4 separate cartridges)
    1998 Polaris 380 pressure-side cleaner w/ 3/4 HP booster pump
    One skimmer :( and one PoolSkim :), One Supervision Galaxy LED pool lamp, Second story solar panels
    Hayward/GoldLine AquaLogic PS4 (replaced 1983 vintage dual circuit Intermatic timer)

  3. Back To Top    #3
    AnnaK's Avatar
    Join Date
    Jul 2007
    Location
    Eastern Pennsylvania
    Posts
    1,134
    Thank you for this post. It validates my decision to get a 2-speed pump.


    AnnaK
    AnnaK

    12,500 gal AGP, Hayward sand filter, Pentair 2-speed pump, timer.
    Please visit our Pool Issues pages for information about step weights, managing the solar cover, and PoolSkim.

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