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Thread: Need Help With Proper Inverter For Sump Pmp

  1. #1
    DIY Junior Member Bendover's Avatar
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    Default Need Help With Proper Inverter For Sump Pmp

    I need help in selected the proper Power Inverter for a sump pump battery backup.
    Im doing this for some elderly family members that are incapable of setting the system up.

    Living in the Northeast we rarely have power failures and using the battery backup may never be needed
    unless flooding occurs with the power outage. That being said, below are the conditions it will be used for,

    The 120V sump pump is located outdoors at the foot of basement stairs, the doorway leading into the basement
    Is at the bottom of the stairs. The concreted area where water collects is about 4 Ft X 4 Ft, with the doorway being
    About6 inches above the concrete. This is where the water can enter the basement. The battery and inverted will be placed on a small table in a waterproof container at the foot of the stairs with the pump plugged directly into it.

    The sump pump is a Little Giant Model 8-CIA (508157), it is 4/10 HP with 10 AMPS and 830 watts.

    The battery is a Deep Cycle Marine 29HM with below rating:
    Amp Hours At 20 Hour Rate = 115
    Cold Crank Amps = 675
    Reserve Capacity = 200 Min

    Now for my question regarding the inverter. I have two models in mind, below are the specs.
    Power Bright Model PW 1100-12 - 9.2 Amps 1100 Watts Continuous 2200 Peak Power
    Power Bright Model PW 1500-12 - 12.5 Amps 1500 Watts Continuous 3000 Peak Power

    The smaller 1100 is fine with the watts but falls short on the amperage needs 10 has 9.2
    The larger 1500 exceeds the specs and is almost double the price.

    My concern is that if the larger 1500 were purchased it would drain the battery much faster.
    The smaller 1100 is good with wattage but short on amperage by .8 amps.

    Can I get away with the smaller model? All suggestions are appreciated.

  2. #2
    Test, Don't Guess! cacher_chick's Avatar
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    The pump current draw will be rising as the battery voltage is falling.

    You might want to check the math on using a 12 volt pump, and then you won't need an inverter at all.

  3. #3
    DIY Junior Member Bendover's Avatar
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    Quote Originally Posted by cacher_chick View Post
    The pump current draw will be rising as the battery voltage is falling.

    You might want to check the math on using a 12 volt pump, and then you won't need an inverter at all.
    Thanks for the reply.

    I want to use the existing pump, the only 12V pumps I am able to find are marine bilge pumps and have plastic impellers that require a separate float switch. The Little Giant pump is heavy duty and does the job well. We're only talking about a 16ft square area here it needs to pump.

    As stated I want to know if can I get away with the 9.2 amp converter when the pump is rated at 10 amp.
    Is the pump drawing at 10 amp constantly or just at startup?
    If constant, I would need to get the larger 12.5 amp inverter and probably risk shorter battery life.

  4. #4
    DIY Senior Member VAWellDriller's Avatar
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    Pumps are all a little different, and the easiest way to know what it really draws is to put an ammeter on it and watch starting and running amps. I use inverters all the time, in service vehicles and to run my hunting cabin off solar....I have all Vector products which I don't even think they make anymore. It's been my experiece that they are slightly under-rated,especially starting a motor, so I would up size. Also, the inverter will only draw enough current to perform the job it's doing, so the battery life should be the same under the same load.

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    DIY Junior Member Bendover's Avatar
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    I don't wish to spend 140.00 for the 12.5 amp inverter as opposed to 80.00 for the 9.2 amp unit since the elderly folks are on a tight budget. Still I don't want to buy the cheaper one if it will not work.

    I was able to download the spec sheet on the Little Giant pump. It shows 830 watts but doesn't say continuous or peak.
    The amps show 10, but only indicates running with no other information. I find it hard to believe a 4/10 HP pump would be using 10 amps. It could be Little Giant is exaggerating to make the pumps sound stronger than it actually is.

    How would I check the starting amps with an ammeter since the pump is sealed?
    By putting the probes on the pumps outlet plug, slightly pulled away from receptacle, this would probably display 15A while connected in that fashion.

  6. #6
    Test, Don't Guess! cacher_chick's Avatar
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    You can check it be measuring the load at the circuit breaker in the panel, or you could split an extension cord so that you can clamp an individual conductor.

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    DIY Junior Member Bendover's Avatar
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    Quote Originally Posted by cacher_chick View Post
    You can check it be measuring the load at the circuit breaker in the panel, or you could split an extension cord so that you can clamp an individual conductor.
    Thanks for the advice but I think I'll just go ahead and buy the 12.5V 1500 watt inverter.
    It’s worth the 60.00 difference in price to have peace of mind that the larger converter can handle the pump.
    The countless hours I've spent researching is wearing on me, although by helping others it will cost me money and time.
    I don't mind doing it since its family.

    I’ve also researched 12V pump kits with battery box and decided those pumps will not be as efficient as the existing pump. It also entails extra work in moving the pump and existing hose.

    The elders son bought the battery, waterproof storage bin and an 800 watt 7.5 amp converter without researching the pumps specs. He had no idea what he was doing so I was asked to help.
    He will be able to return the unopened converter. I will order the new one and do the job since nobody else is capable.

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