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Thread: Replacing 2hp motor with 3hp. Need advice

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    Replacing 2hp motor with 3hp. Need advice

    Hey Guys,
    I'm new to the forum and new to owning a pool. Sorry if this has been answered before, but I can't find the information I need. I recently bought a house with a 15K gallon in-ground pool. The pump that came with the pool was a Pentair Challenger 2HP which had been really loud since I moved in. Since the home was sold as is I didn't get the option to have them replace the motor. I recently came across a good deal on a Whisperflo 3HP (used) which runs very quiet and itís in very good shape. Now I know that a 3HP motor is over killed for the size of the pool, but I guess I couldnít pass on the deal. My concern now is if the 3hp motor can potentially cause problems to internal or external PVC piping.

    The inlets that come from the ground to the 3way valve for skimmer and cleaning are all 2in.
    I only have 3 side jets, a cleaning vacuum line and a skimmer.
    No spa or anything else that would need that much more power.

    The sand filter with the new pump is reading 18PSI, but I haven't backwash in about 2 weeks. I canít backwash it at the moment due to a cracked pipe which I will fix this coming weekend.

    Thanks for your input.

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    bobodaclown's Avatar
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    Re: Replacing 2hp motor with 3hp. Need advice

    Hello,
    It will cost more to run in the long run, but that being said it's working. It shouldn't cause problems. The impeller is what moves the water. The impeller is matched to the motor. It's normally ok to go up in size on the motor but not down. Think of putting a V-8 motor in a small vehicle, over kill. But it you put a small 4 cylinder in to a large vehicle you'll destroy the motor. Kinda the same theory. Most electric single speed pool motors run at 3450 rpm. How much water it moves depends on the size of the impeller and restrictions.
    Bigger impeller and more restrictions needs a bigger motor. Smaller impeller, less restrictions less motor needed.
    Hope that makes sense.
    Bob
    17K Kidney Shaped Pool Concrete (Diamond Bright) Pool, 3/4 hp 2 speed 115V Sta-rite Duraglas PEA5D-180L/P2R5D-181L (Impeller C105-92PS Diffuser C1-216P), 1.5 piping, Pentair CC100 Filter , Heat Siphon 100K BTU Heat Pump Pool Heater, Flow meter Blue White Flowmeter Model No. F-30150P, Hayward Astrolight SP0581N, SWCG CalimarTitanium Edition TE45 , Dolphin Nautilus Plus with CleverClean, Lakeland Florida

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    mas985's Avatar
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    Re: Replacing 2hp motor with 3hp. Need advice

    So are you putting the larger motor on the old Challenger pump? If so, that is fine.
    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

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    JasonLion's Avatar
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    Re: Replacing 2hp motor with 3hp. Need advice

    Welcome to TFP!

    Assuming you replaced the entire pump with a 3 HP pump, it is certainly going to use significantly more electricity than a smaller pump would. It will also put more strain on the filter. You don't say what size your filter is, so I can't tell if the pump is oversized for the filter or not. You run some risk of causing channeling in the filter.

    Your original pump was already significantly too large. Since you don't have a spa or other water features the correct pump for that pool would be a 1/2 HP or 3/4 HP pump.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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    Re: Replacing 2hp motor with 3hp. Need advice

    Thanks for the feedback guys, and sorry for the confusion. I did replace the entire pump not just the motor.

    JasonLion: I'm not sure on the size of the filter right now since I'm a work, but if I had to guess its a Hayward 36 inch. I will double check that later today.

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    Re: Replacing 2hp motor with 3hp. Need advice

    So after looking at my filter last night looks like its the following model
    Hayward Pro-Series S244S
    http://www.hayward-pool.com/prd/In-Grou ... 5516_I.htm

    Effective Filtration Area: 3.14ft
    Design Flow Rate: 62 GPM
    Turnover:
    8hours 29,760 Gallons
    10hours 37,200 Gallons
    50 PSI Max


    so all in all I think the filter should be able to handle the load. I backwashed it for about 2 minutes last night and dropped the PSI from 18 to 15. Other than using more electricity do you guys see any other potential problems like PVC not handling the load, filter blowing up or anything?

    Thank you.

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    Mod Squad jblizzle's Avatar
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    Re: Replacing 2hp motor with 3hp. Need advice

    What size breaker is feeding the pump? Looks like a 2HP Whisperflo could be ~11amps while the 3HP is ~15amps. So, if it is fed by a 15amp service (14AWG wire), that could be a problem as well.

    I have a feeling the extra electrical costs of running the 3HP are going to quickly become more than you would have spent for a 1HP which would likely have been plenty of flow for your pool.
    Jason, TFP Moderator
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    Re: Replacing 2hp motor with 3hp. Need advice

    It has a dedicated 20amp breaker and it runs on 208-230v. I guess I will keep an eye on electric bill and perhaps replace soon if it goes over the top.

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    mas985's Avatar
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    Re: Replacing 2hp motor with 3hp. Need advice

    Quote Originally Posted by optimus310
    so all in all I think the filter should be able to handle the load.
    huh? A 3 HP pump will probably well exceed 62 GPM so no, the filter won't handle the load. Dirt will most likely blow past the filter and you might even break a lateral or two.
    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

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