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Generator too big?

Post in 'DIY and General non-hearth advice' started by tinkabranc, Nov 4, 2007.

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  1. tinkabranc

    tinkabranc Minister of Fire

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    We were given a like brand new 10,000 watt portable generator that has never been used.
    We do have a manual transfer switch in the house already but it is 30 amp 10 circuit which I beleive
    is rated for 7500 max watts. Does it matter that the watts on the generator is higher?
    Can we still use this generator or should we sell it and get a smaller one?
    any help is greatly appreciated

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  2. Corey

    Corey Minister of Fire

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    Ideally, your generator would be rated slightly higher than your switch. That way, the switch will trip before the generator stalls - or trips it's own protection circuits. You should be fine to use it as is.

    One question would be is the generator rated for 10KW continuous or 10KW surge. Often times these days, mfr's will list a 'surge' or 'peak' number just to make an impressive looking ad. Continuous running ratings can be much lower.
  3. tinkabranc

    tinkabranc Minister of Fire

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    The stickers on the generator show 10,000 watts with 12,500 surge watts.
    We were not sure if the max of 7500 on the switch meant that was the max
    it could handle, or if that was the max for generator size.
    We have no information on the switch from the previous owner but it looks
    like it was set up to use on any circuit except our central air.

    thanks for your help
  4. nshif

    nshif New Member

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    You dont have to worry about the line side Amps ( feed side ) only the load side ( house ) . the line side of your elec supply ( from the power co. ) is probably 200 amps and if you only turn on 1 light you are drawing only 5 amps. The only thing to check is if you excede the rated capacity of the transfer switch does it act like a breaker and kick off. If not you will need a breaker between the gen and the transfer switch
  5. velvetfoot

    velvetfoot Minister of Fire

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    That's a pretty nice gift!
  6. begreen

    begreen Mooderator Staff Member

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    Agreed, that is one helluva gift. What is the make and model?

    The generator is definitely oversized for the transfer switch - 28% running and 40% surge. (30amps x 240volts = 7200watts.) So the question is, do you want to use it's full capacity? If yes, it will need a new transfer switch. That's not the end of the world and could add circuits. This could be handy if you have a heatpump. You'll have to answer whether it is worth it or not.

    The important question to answer is how frequently do you see power outages and for how long? If they are rare and short, then the generator is a luxury and a smaller one would suffice. If they are frequent and sometimes long (>1 day) then I'd change the transfer switch and consider adding circuits.
  7. jklingel

    jklingel Feeling the Heat

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    Your generator is WAY TOO BIG! Give it to me and I'll buy you a nice, small one.....
  8. tinkabranc

    tinkabranc Minister of Fire

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    We got it from relatives that upgraded to a permanent standby.
    They told us that if we could not use it, sell it.

    The switch would not be used/needed for whole house at once.
    There are dedicated circuits for fridge, freezer, micro and furnace fan which would
    be the main ones that would be the first needed. The Range, A/C & dryer
    are not listed on the switch cover. Think the rest of the circuits are plugs and
    lights for diff rooms so we could probably use it for pellet stove or window a/c
    too depending on season. 30 amp- 10 circuit- manual.

    generator is a B & S, 18hp 10K watts, electric start, on wheels (thank goodness) and has a cover.
    It is brand new.

    thanks for your help
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