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Thread: Is this portable generator hook-up OK?

  1. #16
    Electrician ActionDave's Avatar
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    Anybody have a problem using one of these? http://www.amazon.com/Coleman-Cable-...ref=pd_cp_hi_1

  2. #17
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Gary in NJ View Post
    OK, now I have a question...

    I'm using L1430C connectors on my cable between the generator and outdoor box. I'm using six feet of 10/4 90C water resistant cable from the generator to the outside hook-up and then an additional 4 feet of the same cable between the outside hook-up and my transfer switch (the very same Square D I referenced above).

    Does this not meet paragraph 2 noted above: "The generator is intended to be connected through permanently installed Listed transfer equipment that switches all conductors other than the equipment grounding conductor."

    My well pump (240V) and other circuits (120V) all work fine with this configuration.
    It could have been compliant when installed but it is no longer compliant to install one today.
    There have been major issues with this type of installation paralleling the neutral and equipment grounding conductor between the transfer and the generator itself. This leaves the frame of the generator at the same level as the circuit being supplied.

    If the neutral was lifted from the frame of the generator and one leg of the 240 volts then shorts to the frame of the generator there is no fault current path to open that leg and then the equipment grounding conductor of the generator is raised to the same level as the shorted leg.

  3. #18

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    So should I ground the frame of the generator to the ground cable at the breaker panel?

  4. #19
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by Gary in NJ View Post
    So should I ground the frame of the generator to the ground cable at the breaker panel?
    If your generator has the receptacles mounted on the frame of the generator then the neutral point of that generator winding should be bonded to the frame.
    The grounding terminal of the receptacles mounted on the generator is also bonded to the frame.
    In the event of a ground fault the faulted current travels back to the frame on the equipment grounding conductor and from the frame to the neutral point of the generator winding causing a high current draw which opens the overcurrent device which on most generators is a reset button.

    To connect this generator to the wiring system of our business and homes causes a parallel path between the equipment grounding conductor and the neutral as the service disconnect will have this same bonding as is found on the generator. When the equipment grounding and neutral become tied together at the service it makes the equipment grounding conductor in the cord connecting the generator to the building carry part of the current that is carried on the neutral and this makes the frame of the generator at the same potential as the circuit or 120 volts.

    To relieve this parallel path some will lift the neutral from the frame of the generator and let it float so to speak. When this is done and one winding of the generator short to the frame there is nothing to shut down the overcurrent device or the generator and the equipment grounding of the generator is energized to 120 volts. Now we have 120 volts supplying the 120 volt receptacles and the other 120 volts supplying the equipment grounding conductor or we have 240 volts at the 120 volt receptacles.

    This is why that UL has made the changes to their listing of how to install one of the self-contained generators where we can no longer use these type of installations and the generator MUST be installed as a Separately Derived System or the use of cords for each appliance must be used.

  5. #20

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    Got ya. Thanks for the detailed description.

  6. #21
    DIY Junior Member illinois524's Avatar
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    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?

  7. #22
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by illinois524 View Post
    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?
    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.

  8. #23
    DIY Junior Member illinois524's Avatar
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    Quote Originally Posted by jwelectric View Post
    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.
    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?

  9. #24
    Jack of all trades DonL's Avatar
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    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...
    Theory only works perfect in a vacuum.

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  10. #25
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by illinois524 View Post
    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?
    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 by leejosepho; 12-07-2011 at 04:40 AM.
    "Great minds discuss ideas, average minds discuss events and small minds discuss people." --Eleanor Roosevelt

  11. #26
    Electrical Contractor/Instructor jwelectric's Avatar
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    Quote Originally Posted by illinois524 View Post
    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?

    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.

  12. #27
    DIY Junior Member illinois524's Avatar
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    Quote Originally Posted by leejosepho View Post
    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.
    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.

  13. #28
    DIY Junior Member illinois524's Avatar
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    Quote Originally Posted by jwelectric View Post
    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.
    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.

  14. #29
    Electrical Contractor/Instructor jwelectric's Avatar
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    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.

  15. #30
    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by illinois524 View Post
    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.
    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.
    "Great minds discuss ideas, average minds discuss events and small minds discuss people." --Eleanor Roosevelt

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