Is this portable generator hook-up OK?

Discussion in 'Electrical Forum discussion & Blog' started by mbwayne, Oct 20, 2011.

  1. illinois524

    illinois524 New Member

    Messages:
    9
    Location:
    new jersey
    so could you simply go from generator---hook up to outside power box---then run #10/3 wire to a 6 breaker sub panel---splitting the 10 wire inside the sub panel (one hot wire to each leg-neutral to buss bar and ground to separate buss bar) thus creating 6 or so separate circuits with there own breakers at 120v each and then running outlets to strategic locations in the house similar to the way a house is wired but this system would be for generator use only never touching the existing panel wiring? would this not be like running extension cords?
  2. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,559
    Location:
    North Carolina
    Here is the code section that governs generatros that has receptacles mounted on the frame of the generator. Pay close attention to the Note at the bottom

    250.34 Portable and Vehicle-Mounted Generators.
    (A) Portable Generators. The frame of a portable generator shall not be required to be connected to a grounding electrode as defined in 250.52 for a system supplied by the generator under the following conditions:
    (1) The generator supplies only equipment mounted on the generator, cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and
    (2) The normally non–current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are connected to the generator frame.
    (B) Vehicle-Mounted Generators. The frame of a vehicle shall not be required to be connected to a grounding electrode as defined in 250.52 for a system supplied by a generator located on this vehicle under the following conditions:
    (1) The frame of the generator is bonded to the vehicle frame, and
    (2) The generator supplies only equipment located on the vehicle or cord-and-plug-connected equipment through receptacles mounted on the vehicle, or both equipment located on the vehicle and cord-and-plug-connected equipment through receptacles mounted on the vehicle or on the generator, and
    (3) The normally non–current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are connected to the generator frame.
    (C) Grounded Conductor Bonding. A system conductor that is required to be grounded by 250.26 shall be connected to the generator frame where the generator is a component of a separately derived system.
    Informational Note: For grounding portable generators supplying fixed wiring systems, see 250.30.
  3. illinois524

    illinois524 New Member

    Messages:
    9
    Location:
    new jersey
    In trying to learn this it's like going to a lawyer to get a will made. Hard to grasp all this jargon. What I'm looking for is this to be explained or broken down in much easier terminology. I quess what I'm hearing is that there would be no way for an over load to be tripped by removing the frame ground---is this correct. If this is the case then would my example above (post #21) work as each new circuit coming out of the new sub panel would have it's own breaker that would trip in case of a fault thus not go back to the frame? Am I thinking right or am I still not learning anything?
  4. DonL

    DonL Jack of all trades Master of one

    Messages:
    4,442
    Location:
    Houston, TX
    Really the Bottom line is that you should not feed a House with a Portable Generator.

    Everything should be run on an Extension cord.

    A REAL Generator made for that purpose will normally be installed properly by a Professional that knows. Where You live makes a BIG difference. Not all codes are the same.

    During a real Emergency, You can do whatever it takes.

    If You try to Understand the Codes you can just become lost in the BS and numbers.

    Be careful and get a Pro, Because learning NEC or UL Rules will make the average person do it wrong most of the time.


    It is not Rocket Science like all the codes make it out too be...
  5. leejosepho

    leejosepho DIY scratch-pad engineer

    Using 10/3 (or whatever proper size) and a ground wire, that is essentially how things are done in a circus or carnival where "extension cords" are run wherever needed. Your theory here is mechanically sound, but you will likely never convince anyone (such as inspector) there is absolutely no possibility of your generator ever sending power back out to the pole and possibly injuring or killing a lineman trying to restore power during an outage.
    Last edited: Dec 7, 2011
  6. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,559
    Location:
    North Carolina

    Yes what you suggest would work but there would be some problems with the method being used.

    The problem is those extra circuits you have installed are now part of the premises wiring simply because they are attached to and installed in the building. It makes no difference that they are not supplied by the utility company or not.

    The NEC requires that any premises wiring system be connected to earth as outlined in 250.20(B). The conductor that is to be connected to earth (the neutral) is outlined in 250.26.

    The generator that is being installed is a stand-alone power source with over current and devices installed on them. UL Standard 2200 mandates that this type of generator must have the neutral bonded to the frame.

    Doing the bonding at the generator will not allow the bonding to be done again anywhere downstream see 250.24(A)(5).

    This information along with the Informational Note under 250.34(C) and the information found in the UL White Book (see FTCN) will require that the generator be connected to the building via a transfer switch that also transfers the grounded neutral conductor.

    In summery what you propose will gain nothing more than the added work and expense of the extra installation as well as various other code issues.
  7. illinois524

    illinois524 New Member

    Messages:
    9
    Location:
    new jersey
    I know you never say never but holy cow how in the heck with this set up can it ever back feed to the power lines when it is it's own self contained system. You would need an extension cord with both ends having male ends in order to plug the gen outlet into the regular house outlet to back feed to the outside.
  8. illinois524

    illinois524 New Member

    Messages:
    9
    Location:
    new jersey
    So lets just say for fun this system was able to float in mid air never touching the building structure. With that in mind then there would be nothing wrong with it cause it wouldn't be in violation of any codes CORRECT thus it would be like a bunch of romex® extension cords.
  9. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,559
    Location:
    North Carolina
    It would still be on or in the premises so thereby being part of the premises wiring system and would need to comply with the entire electrical code.
  10. leejosepho

    leejosepho DIY scratch-pad engineer

    Correct, and now think of the lineman working out at the street and he comes over to ask you to stop your generator while he repairs things at the pole. The only way you are going to convince him there is absolutely no way for your generator to injure him is by turning it off. He is not going to ask, care about or come in to see anything else for himself. My point is not that you are doing anything dangerous, but that you will never convince everyone else it is safe.
  11. illinois524

    illinois524 New Member

    Messages:
    9
    Location:
    new jersey
    I can certainly understand that and would oblige them by turning it off.
  12. Rich B

    Rich B DIY Senior Member

    Messages:
    283
    Location:
    New Jersey
    I think you need to keep in mind that lineman generally work on live wires at the pole and at your service connection.

    Primary side....above the transformers in a residential area around here is 12,500volts leg to leg I do believe....7,200 single leg to ground. There are usually fuses on the primary side but not on the secondary..... A heck of a lot of current is available there and it still amazes me to see what that can do if it shorts to ground.....I recently found an area on a concrete driveway that a secondary drop came down on when something severed the cables across a highway near my home. I was jogging.......The concrete was chattered deeply as if an air hammer did it and it was black-end and some of the material around it literally turned to glass....I scooped some up and saved it.....

    Of course having 2 live voltage sources being potentially connected is a big danger and not something they would expect to have happen as they were working....but then if you had energized your houses service and it fed back up to the pole you really have created a bad situation....
    Last edited: Dec 13, 2011
  13. leejosepho

    leejosepho DIY scratch-pad engineer

    I think it was here in this forum where someone said a lineman once insisted a generator be stopped even though the homeowner had a code-compliant switch completely isolating it from the regular service.
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