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Thread: Frankensteined Pump - Should I change the impeller while installing new VS motor?

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    ChuckDavis's Avatar
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    Aug 2010
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    Frankensteined Pump - Should I change the impeller while installing new VS motor?

    I'm installing my new EcoTech VS 1.5 HP motor on my Hayward SuperPump, and ran into a bit of confusion.

    The pool was installed somewhere in 1997-2000 by the original owner of the house, who was also a pool builder. It appears that he Frankensteined the pump assembly.

    The pump body is a Hayward SuperPump, Model No. SP2621X25, which is supposedly a 2.5 HP model. (Although I suspect that the same pump body is used for various HP ratings.)

    The motor is an A.O. Smith 1.5 HP, 2-speed unit with a Service Factor of 1.3.

    The impeller is a Hayward SP2610-C, which is rated at 1.0 HP.

    The piping is 1.5 inch. The pump/filter/heat pump are 4-5 feet above water level. There is 22 lbs. of back pressure (!) from the filter (Tagelus TA-60, Zeolite that was just cleaned, newish multiport valve). There is a 30 foot run to/from the heat pump, which adds even more head when the heat pump is in-circuit during the summer.

    With the heat pump bypassed in winter, I could run the pool, water feature and (just barely) Liquidator with the motor on low speed. With the heat pump in-circuit, I had to run the motor on high speed.

    As part of installing the new EcoTech VS motor (1.5 HP, Service Factor 1.6), should I change out the impeller for a 1.5 HP rated impeller? I'm looking for maximum energy efficiency while keeping all the pool systems running properly.
    15,000 gallon IGP, epoxy surface, waterfall, borates (!), not closed in winter
    SuperPump with 2.4 THP EcoTech variable speed motor, Tagelus TA-60 filter with zeolite media, Liquidator, AquaComfort heat pump, Blue-White flowmeter, Smartpool Wall Climber
    TF-100, LaMotte metal sequestrant test kits
    Sundance Capri hot tub

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    Re: Frankensteined Pump - Should I change the impeller while installing new VS motor?

    I don't think that the bigger impeller would give you any benefit. You should be able to get more than enough flow from that impeller at less than full rpm.

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    JasonLion's Avatar
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    Re: Frankensteined Pump - Should I change the impeller while installing new VS motor?

    Leaving in the smaller impeller is both fine, and will be (just slightly) more energy efficient. Using a larger motor with a smaller impeller is always fine. You never want to use a motor with an impeller designed for a larger motor. Using your existing impeller will give you the same maximum water flow that had before, and let you go to lower effective speeds, which are more efficient.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    ChuckDavis's Avatar
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    Re: Frankensteined Pump - Should I change the impeller while installing new VS motor?

    I scurried down to the pool store before they closed and grabbed a 1.5 HP impeller just to have options. Then I dove back into Google.

    This paper caught my eye (http://www.pump-zone.com/topics/pump...-impeller-trim), and especially one of the conclusions: Efficiency decreases with a reduction in speed. However, this reduction in efficiency with speed is small, while the reduction in efficiency by trimming the impeller can be substantial.

    Is it a correct interpretation of this paper that for a given flow and head I will use less net energy with the larger impeller and the motor running at a lower speed than with the smaller impeller and the motor running at a higher speed?
    15,000 gallon IGP, epoxy surface, waterfall, borates (!), not closed in winter
    SuperPump with 2.4 THP EcoTech variable speed motor, Tagelus TA-60 filter with zeolite media, Liquidator, AquaComfort heat pump, Blue-White flowmeter, Smartpool Wall Climber
    TF-100, LaMotte metal sequestrant test kits
    Sundance Capri hot tub

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