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Will a battery backup (UPS) manage pump startup current?

  1. May 19, 2016 #1

    Grinkle

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    I have a still unwired pump at the end of a new drain outside my house. The startup current required of the pump is significantly higher than the steady state current required. If I put a UPS between the pump (the pump has a standard 110V plug) and the outlet, will this reduce the max additional current required of my house circuit to roughly the steady-state need of the pump?

    I don't want to require a new circuit breaker in my box just to accommodate getting the pump going a couple times a year if I can avoid it.
     
  2. jcsd
  3. May 19, 2016 #2

    davenn

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    since you haven't stated the steady running current of the pump, nor stated the current capabilities of the UPS
    it's a bit difficult to answer your Q

    how about a bit more information please :smile:


    Dave
     
  4. May 20, 2016 #3

    CWatters

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    I think some UPS have a bypass so that the inverter is only used during a power cut. Others use the inverter to generate the output all the time. If you have the former then any surge will be drawn from the incoming and the UPS won't achieve the desired result. If it's the latter type then it will work as long as the UPS can handle the surge.

    Personally I'd get the circuit breaker upgraded.
     
  5. May 20, 2016 #4
    How big of a pump ? End of a drain? -- Have you considered a drive, depending on the application it may pay for itself in electricity..
     
  6. May 22, 2016 #5

    Grinkle

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    Thanks for the replies - I'll take a look at specific UPS devices, talk to an electrician about what a new breaker would entail and decide which path to take.
     
  7. May 22, 2016 #6

    jim hardy

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    Does your pump motor nameplate have an entry "Code" or "KVA Code" ? Or one "LRA" for Locked Rotor Amps) ?
    That'll give you its staring current.

    A ferroresonant "Sola Transformer " will do what you want, limit motor current during start.
    A UPS might do it or it might go up in smoke.

    Why do you want to limit start current ? It doesn't flow very long. Your breaker and wires should be sized something like 125% full load current, not starting current. Does the nameplate say what size fuses to use ?
    http://ecmweb.com/design/motor-calculations-part-1-motors-and-branch-circuit-conductors
     
  8. May 23, 2016 #7

    billy_joule

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    I don't know how USA domestic power works but in NZ & AU appliances, by law, must have the appropriately sized plug.
    Surely you can't sell a pump with a plug that connects to a circuit that cannot provide the required current?

    Or are you saying the available circuit is already close to it's rated capacity with demand from other appliances and the pump will push it past capacity?
     
  9. May 23, 2016 #8

    Grinkle

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    Yes, this is my concern.
     
  10. May 23, 2016 #9

    billy_joule

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    Ok, so inrush current is not your concern? household breakers have allowance for inrush current as domestic appliances with (relatively) high power motors are common place.

    If the circuit is regularly close to capacity then can't you put the pump on a different circuit? or put whatever is bringing that circuit close to capacity on a different circuit?
    If the pump only runs a couple times a year is it really an issue if you can't run whatever other high current device you have on that circuit? Have you done any testing?
     
  11. May 23, 2016 #10

    Grinkle

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    All valid questions, to be sure. I am hoping I can find a way to over margin. More detail below.

    Inrush current during pump startup will present the max load to the breaker. I do not know what other lights or appliances are already on the circuit that is most convenient to wiring up the pump, and I am wanting to assess which approach to suggest (new circuit breaker in the box vs add pump to already existing circuit) to an electrician before calling him.

    I might test with an extension cord, and I might be able to not trip the breaker. Still, if adding a UPS would provide additional margin, I would add it in. If it would be pointless and not provide any benefit, I would not pursue that approach. I will definitely test in any case before calling someone to do the wiring.

    I have an outdoor outlet that is about 50 feet from the pump, and the breaker box itself is about as far away from the pump as it can be and still have both on my property. I might be able to find access to any arbitrary breaker in the box if I drill the right hole in some wall, but finding it would be inconvenient to say the least. And I don't have any map of which loads in my house are assigned to which breaker in the first place. I am hoping to avoid needing to figure all that out by adding lots of margin to the most convenient solution, which is to run a wire from the nearest outdoor outlet to the pump.

    Its good information for me that breakers themselves will tolerate some amount of inrush - thanks for that.
     
  12. May 24, 2016 #11

    billy_joule

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    Well the electrician will first check whether the most conveniently placed installed circuit can have an additional outlet installed (including cable run length derating) and still meet the local code. If it can, he should assess whether it's wise; if there are high draw appliances (heaters, power tools etc) already on that circuit then he may advise against it. Though, that is outside of his scope as whatever portable appliances you plug in isn't under his jurisdiction - as long as the installed circuit meets the code, he's done his job. In my country that's twelve double outlets (so 24 240V 10A outlets) per 20A power circuit breaker, it drops to 3 double outlets if they service kitchens &/or laundries.
    In the somewhat unlikely event all current circuits have the max number of outlets a new circuit is required, this doesn't necessarily mean running a new cable right from the breaker box. It could mean fitting a new breaker, moving a cable or two in the breaker box to balance outlet numbers and running the new cable from your existing outlet that's closest to the pump.
    It might be a job done in an hour or two (provided you dig the trench..) or it could be days - If your houses' wiring is old and doesn't meet modern requirements your electrician may be legally obligated to make the necessary upgrades at your cost ( I'd assume the USA has some sort of rolling upgrades regulations to improve safety).

    The UPS is a definite kludge and should be avoided.
    If the pump meets your local code for portable appliances (eg you didn't buy it off some dodgy offshore website and plan on using it with a travel adaptor) then you can safely plug it in wherever it'll fit, forget about inrush current.
     
  13. May 24, 2016 #12

    jim hardy

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    Have we ever heard what is the size of this pump ? Its FLA LRA Starting KVA ?



    If this is a little 3 amp sump pump we're wasting time.
     
  14. May 24, 2016 #13

    Grinkle

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  15. May 24, 2016 #14

    jim hardy

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    That's just a little more than a medium size refrigerator. My kitchen fridge i measured 13 starting 6 or 7 running .

    sounds to me like
    billy_joule's advice is right on.
     
  16. May 24, 2016 #15

    rbelli1

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    A ups that will be able to handle that load will be somewhere in the $1000 range and $100-$200 every 5 years maintenance. This assumes that the initial inrush will not trip the over-current protection in the UPS. It may be many times that cost.

    You will likely void the warranty and reduce the service life by using it in that application. It is pretty much the wrong choice.

    BoB
     
  17. May 24, 2016 #16

    Grinkle

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    Thanks, advice accepted.
     
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