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Sump pump power draw

Discussion in 'Homeowners Corner' started by twubs, Aug 26, 2011.

  1. twubs

    twubs New Member

    Nov 14, 2010
    Likes Received:
    I don't wnat to panic but I also don't want to have to manual drain the sump pump either.
    I didn't look this morning but assuming my sump is 1/2 HP. What would the minimum generator size be to keep that running? I bought the last portable generator from Home Depot but it is only 1850W.

    Is this thing going to work?
  2. flynnibus

    flynnibus Well-Known Member Forum Staff

    Oct 29, 2002
    Likes Received:
    look for a current draw (Amps) on the motor.. that will get you closer to the answer then a theoretical hp -> watts conversion.

    The startup of the motor will also be higher a higher load then the continuous draw of the motor. Since a sump pump starts and stops frequently... that can mean lots of spikes

    1/2 hp is 373 watts. If the motor is like 80% efficent, then your continuous could be 373/0.8 = 466 watts. But they say the startup draw can be 1.5x-2x the continuous draw.. so you might consume up to 900+ watts. That's roughly 7.8 Amps. Compare that with details you can find on your pump about amp draw.

    Watts = Voltage x Amps

    Assuming 115v or 120v for your pump's input.. you should be able to work with that
  3. Mom8386

    Mom8386 Member

    Aug 19, 2007
    Likes Received:
    It's the reason we bought a battery back-up sump a few years ago.
  4. Mike-and-Kim

    Mike-and-Kim Member

    Feb 22, 2009
    Likes Received:
    Still have not checked the battery powered sump of the list of things to do...

    Decided to measure our sump to see how much current it took. Completely pegged my old GR Variac on the 5A range, which I like to use since it has a much faster response than these "Kill a Watt" gadgets.

    The result was ~8.8A, which since this is a reactive load will be a bit less in terms of actual power.


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