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  1. #1
    Join Date
    Aug 2010
    Posts
    15

    30 amp receptacle for 5000 watt generator

    This may be a dumb question....but I am considering buying a backup generator which has a max output of 5000 watts, and running it to a transfer switch (for use with only 120 volt circuits). I noticed that the main receptacle on the generator (the receptacle that would be used with the transfer switch) is 3-pronged and rated 30 amps/125volts. Wouldn't that limit the usable generator output to approx 3750 amps, wasting the remaining capacity of the generator? Or is there something I do not understand?

    Thank you!!!!

  2. #2
    Join Date
    Nov 2007
    Location
    Texas
    Posts
    231
    If its a three prong 125 vac 30 amp outlet then you won't be able to get the 5000 watts. More like 3600 or 3750 watts. My generator has a 30 amp 4 prong 240 vac 30 amp outlet that I hooked up to a manual transfer switch. My generator is rated for 7000 watts running and 9000 starting watts.

  3. #3
    Quote Originally Posted by hvacques1 View Post
    This may be a dumb question....but I am considering buying a backup generator which has a max output of 5000 watts, and running it to a transfer switch (for use with only 120 volt circuits). I noticed that the main receptacle on the generator (the receptacle that would be used with the transfer switch) is 3-pronged and rated 30 amps/125volts. Wouldn't that limit the usable generator output to approx 3750 amps, wasting the remaining capacity of the generator? Or is there something I do not understand?

    Thank you!!!!
    5000 max ?

    Electrical devices are rated to 80% continuous load . Which would be 4000 watts .

    So , you are looking at 400 watts difference .

    Be sure to use # 10 copper wire on the cord with the male 30 amp 125 VAC cord cap .

    Does the generator have a circuit breaker on this 30 amp circuit ?

    God bless
    Wyr

  4. #4
    You don't know anything unless you get a schematic of the generator. I have seen some of these where they are wound so that the generator has doubled up windings and a bunch of taps on the generator that feed different outlets, so while you won't be able to get 5000 watts on any one outlet, the wattage you can get if you use all outlets on the generator totals up to 5000. Note that it isn't optimal to run a generator in an unbalanced manner where all power is taken off a single winding, but they get away with it on the small units because most of the time the loads are intermittent (contractors saws and the like) and small. And yes it is certainly underhanded marketing but it sounds like your looking at a generator aimed at the residential and contractor market, where spec inflation is rampant.

  5. #5
    Join Date
    Aug 2008
    Location
    New Jersey
    Posts
    67
    Might want to read up on a generator interlock kit for your main panel. The big box stores push the transfer switches which I am not really a fan of. The interlock kit is UL approved, and locks out the main breaker when the generator outlet is on. Only thing I would add is some gauges to measure volts, amps, and hertz.

  6. #6
    Join Date
    Jul 2013
    Location
    NJ
    Posts
    10
    It's odd to have a 5KW generator with only a 120V output. You sure there isn't also a 120/240V 4 prong receptacle?

  7. #7
    Join Date
    Jul 2013
    Location
    NJ
    Posts
    10
    Quote Originally Posted by sdeery View Post
    Might want to read up on a generator interlock kit for your main panel. The big box stores push the transfer switches which I am not really a fan of. The interlock kit is UL approved, and locks out the main breaker when the generator outlet is on. Only thing I would add is some gauges to measure volts, amps, and hertz.
    Interlocks are the way to go. I've installed over 150 of them and my customers are always extremely happy.

  8. #8
    Join Date
    Nov 2008
    Posts
    1,673
    Quote Originally Posted by hvacques1 View Post
    a max output of 5000 watts
    rated 30 amps/125volts.
    Wouldn't that limit the usable generator output to approx 3750 amps
    The service lifetime of the receptacle may not be as long as receptacle designers wished but what gen. user can say for sure that he or she was short-changed?
    These guys are playing the odds.

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