Grounding a portable generator

Discussion in 'Electrical Forum discussion & Blog' started by Cubey, Nov 9, 2007.

  1. Cubey

    Cubey New Member

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    What about the idea of just bonding neutral to ground in the trailer's panel and then bonding the ground terminal on the generator to the generator's frame?

    That would basically do the same thing as bonding the generator's neutral to ground and then bonding that to the generator frame. Only difference really would be the trailer would be bonded at RV parks as well unless I remove the bonding screw every time I switch between RV park and generator.

    Here is a diagram I have created to illustrate what I mean:
    [​IMG]
    Red=hot, blue=neutral, green=ground

    Only thing I should point out about the digram that it is slightly incorrect is that I would be bonding ground on the generator to the frame at the external ground terminal, not at the outlets/panel.
     
  2. jwelectric

    jwelectric Electrical Contractor/Instructor

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    NO! NO! NO!

    250.34 Portable and Vehicle-Mounted Generators.
    (C) Grounded Conductor Bonding. A system conductor that is required to be grounded by 250.26 shall be bonded to the generator frame where the generator is a component of a separately derived system.

    The words grounded conductor in (C) is referring to the neutral and it MUST be bonded to the generator frame.
     
  3. Cubey

    Cubey New Member

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    Problem is there is no one who will even do it! I've called every possible place. I've called electricians, small engine repair shops, RV places. No one will do it. What more can I possibly do if no one will do the modification for me aside from attempt to do it myself?

    I found the following at: http://www.emergencypower.com/generatorhookup.html

     
    Last edited: Dec 20, 2007
  4. Cubey

    Cubey New Member

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    You know, a very good question comes into play. The generator has circuit breakers on it and the generator is made with floating neutral. The breakers somehow work without bonding (perhaps through grounding to earth). Seems to me the generator was considered a more heavy duty model when it was made. It has a Briggs & Stratton Vanguard engine which seems to be (or was at the time) pretty much their top of the line engine for portable generators. Coleman made this generator to be a workhorse. It has DUAL 120v/30A *and* a seperate 240V/20A hook. It's not a single outlet shared by a switch.

    I guess the point I am getting at is the generator was designed to function as floating and be safe in heavy duty applications. Changing it might damage the electrical system or make the breakers not work properly.

    I guess since my choices for what to do about it have pretty much run out (no one in this crappy town will even touch it except the electrician I know who can't/won't due to the engine being in the way) I will just have to use it as floating and ground it with a big metal tent stake so it will have SOME ground path to earth. That along with a GFCI adapter plugged in at the generator will just have to do. I will have done everything I possibly could to make the generator safe since no one will bond neutral on it.
     
  5. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    Conventional CBs don't care about grounding, bonding, etc. They just open when the current through the hot leg exceeds their design value for the design time, regardless of where it's going.
     
  6. jwelectric

    jwelectric Electrical Contractor/Instructor

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    In the event of a ground fault on an unbonded system how will it draw enough current to open the circuit breaker?
     
  7. Cubey

    Cubey New Member

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    That is kind of my point. They made this portable generator with breakers that are meant to actually work without neutral being bonded somehow. Strange, huh? Unless the act of grounding the generator to earth somehow comes into play.
     
  8. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Any breaker or fuse will open when the current draws hits a level greater than what it is designed to carry. If I had a 15 amp fuse and I installed an electric heater that draws 3000 volt amperes then the 15 amp fuse will open.
    If I have a 15 amp fuse protecting a circuit that is not bonded to the source and a ground fault occurs (the hot touches metal) then the fuse will never open.
    It is through the bonding of the metal to the source that establishes a low impedance path for the current to return to the source which initiates the high current draw that makes the device open

    As I have pointed out before the connection to earth plays NO part in the operation of the overcurrent device. All that the connection to earth does is;
    250.4 General Requirements for Grounding and Bonding.
    The following general requirements identify what grounding and bonding of electrical systems are required to accomplish. The prescriptive methods contained in Article 250 shall be followed to comply with the performance requirements of this section.

    (A) Grounded Systems.
    (1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.
    (Remember that "grounding is nothing more than a connection to earth)

    (2) Grounding of Electrical Equipment. Non–current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected to earth so as to limit the voltage to ground on these materials.

    (3) Bonding of Electrical Equipment. Non–current-carrying conductive materials enclosing electrical conductors or equipment, or forming part of such equipment, shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path.
    (4) Bonding of Electrically Conductive Materials and Other Equipment. Electrically conductive materials that are likely to become energized shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path.

    (5) Effective Ground-Fault Current Path. Electrical equipment and wiring and other electrically conductive material likely to become energized shall be installed in a manner that creates a permanent, low-impedance circuit facilitating the operation of the overcurrent device or ground detector for high-impedance grounded systems. It shall be capable of safely carrying the maximum ground-fault current likely to be imposed on it from any point on the wiring system where a ground fault may occur to the electrical supply source. The earth shall not be considered as an effective ground-fault current path.
     
  9. Cubey

    Cubey New Member

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    I'm sure you'll say no to this as well, but what about making a twistlock dummy plug that links neutral to ground at the generator's outlet? Preferabley I would use the the 240V outlet since I will never have a need for 240V. It would be plugged it prior to starting the generator and remain there until the generator is shut down (in case I wished to remove it to use the outlet).

    It wouldn't be the *proper* way to do it but if it gets the job of bonding done safely and easily, whats the harm?

    I would also wire a big tent stake to the ground terminal and to the generator's frame just to help bleed off any buildup that may occur and use a plugin GFCI adapter on the cord that plugs in the trailer.

    If nothing else, that might do just until I can find someone who will actually work on the generator to bond it properly. I would hate for the generator's electrical system to be damaged by bonding it however if it's thats a possibility.
     
    Last edited: Dec 21, 2007
  10. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    I assume you aren't talking about "ground fault" in the GFCI sense, since obviously it doesn't care about grounding or bonding either. A GFCI would work properly.

    If the ungrounded, unbonded generator uses conventional (non-GFCI) breakers, and someone standing in a puddle grabs a hot wire, I'm frankly not sure what would happen, but I'm guessing not much. That may, in fact, be why they're built that way. Since the generator produces a potential difference only with respect to itself (the return leg) there's no reason to suspect there would be a measurable (or feelable) voltage between a generator "hot" leg and "real" ground. There's also no real distinction between the two legs on such an outlet -- there's only a voltage difference between them, not between either of them and anything else.

    Right. The only "protection" the breaker offers in the unbonded, ungrounded generator is overcurrent protection -- it's to protect the gernerator, not the operator or innocent bystanders.
     
    Last edited: Dec 21, 2007
  11. jwelectric

    jwelectric Electrical Contractor/Instructor

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    The way that I am going to post this will take a little understanding on your part.
    What you are now thinking about as being the equipment grounding conductor (the green wire in the cord) will not be an equipment grounding conductor due to the fact that you are using a generator instead of a utility service.
    To justify this statement I read 250.34(A) (2) The non–current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame.

    They are not connecting to earth.

    250.24 Grounding Service-Supplied Alternating-Current Systems.
    (A) System Grounding Connections.
    A premises wiring system supplied by a grounded ac service shall have a grounding electrode conductor connected to the grounded service conductor, at each service, in accordance with 250.24(A)(1) through (A)(5).
    Instead of having a grounding electrode (your tent stake) installed we are told,

    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 non–current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame.

    If we want to drive a grounding electrode we are allowed to do so as long as the electrode conforms to 250.52. This is what is meant with the use of “shall not be required†and “a grounding electrode as defined in 250.52.†Your tent stake would be nothing but a waste of time.

    We also need to remember what the grounding electrode is installed for,
    250.4 General Requirements for Grounding and Bonding.
    The following general requirements identify what grounding and bonding of electrical systems are required to accomplish. The prescriptive methods contained in Article 250 shall be followed to comply with the performance requirements of this section.
    (A) Grounded Systems.
    (1) Electrical System Grounding.
    Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

    The purpose of protecting the system from lightning is the same as it is for unintentional contact with higher-voltage lines. All of this will take place on the line side of the service and is not likely to happen to a portable generator therefore no need to have the electrode.

    As to the bonding of the system; this is done to establish a path from any and all metal exposed to the touch in the system including the screws that holds device plate covers in place.
    This bonding is required to occur in the service.
    250.24 Grounding Service-Supplied Alternating-Current Systems.
    (A) System Grounding Connections
    . A premises wiring system supplied by a grounded ac service shall have a grounding electrode conductor connected to the grounded service conductor, at each service, in accordance with 250.24(A)(1) through (A)(5).

    As outlined above the generator will not be grounded (connected to earth) instead the grounded (neutral) will be bonded to the frame.
    250.34(C) Grounded Conductor Bonding. A system conductor that is required to be grounded by 250.26 shall be bonded to the generator frame where the generator is a component of a separately derived system.

    The purpose of this bonding of the neutral point (grounded point) is to establish a path back to the source from the equipment grounding terminal of the receptacle which is to be bonded to the frame of the generator.
    250.34(A) (2) The non–current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are bonded to the generator frame.

    This bonding to the frame makes the frame the main bonding jumper as outlined;
    250.24 (B) Main Bonding Jumper. For a grounded system, an unspliced main bonding jumper shall be used to connect the equipment grounding conductor(s) and the service-disconnect enclosure to the grounded conductor within the enclosure for each service disconnect in accordance with 250.28.

    As outlined this bonding jumper must take place in the service equipment. The generator is the power supply and the first disconnect in its line becomes the main disconnect, the breaker or reset protecting the receptacle on the generator.
    Also this bonding jumper is required to be unspliced and each place that it would plug into a receptacle would be a place that it could be broken losing the bonding. Therefore the bonding is not allowed to be done in the RV.
    The bonding must take place in the service equipment and the bonding conductor must be unspliced.

    This is also required when the generator is being used as a separately derived system.
    250.34(C) Grounded Conductor Bonding. A system conductor that is required to be grounded by 250.26 shall be bonded to the generator frame where the generator is a component of a separately derived system.

    The generator is a separately derived system because it conforms to the definition.

    Separately Derived System. A premises wiring system whose power is derived from a source of electric energy or equipment other than a service. Such systems have no direct electrical connection, including a solidly connected grounded circuit conductor, to supply conductors originating in another system.


    So far we have learned that the bonding is required to be done at the generator and that a grounding electrode is not required. If the system does not have a grounding electrode then there can not be any equipment grounding conductors. The purpose of the equipment grounding conductor on a grounded (connected to earth) system;
    250.130 Equipment Grounding Conductor Connections.
    (A) For Grounded Systems.
    The connection shall be made by bonding the equipment grounding conductor to the grounded service conductor and the grounding electrode conductor.

    Instead of bonding to the grounding electrode conductor we are bonding to the frame. This is the only time that the green/bare conductor is an equipment bonding conductor instead of an equipment grounding conductor.





    Remember that the statements above are minimum safety standards and to do anything less would be below the minimum safety standard. It is your life and the lives of your loved ones that your are trying to protect so I shall leave the rest in your hands.
     
  12. Cubey

    Cubey New Member

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    Okay, so if a grounding rod (electrode) is completely optional on a portable generator I won't have to deal with it. Great. And the only time it might be a problem in a camping situation is lightning but I won't be running it in rain/storms so that's a non-issue.

    Okay, here is what is confusing me. The electrician who had I look at it was stumped by the terminal saying "ground" not "grounding" on it. Here is what the Coleman manual says about it:

    Here is a diagram from the manual showing where the terminal is located on my generator:
    [​IMG]

    The generator is completely isolated from the frame as far as I can tell by rubber things between it and the frame/bolts holding it on. That's easy enough to fix with some wire going from the lug to a clamp on the exposed metal frame. But if that's truly a ground lug (green wire/3rd prong) it won't do me any good I don't guess to bond that to the frame. Neutral will still be floating. That is the dilemma I have. I would have to travel who knows how many miles to even find someone who will work on this damn generator to bond neutral to frame/ground. It would be a heck of a lot easier to just take the generator apart and bond it myself.

    For all I know too, someone may have already had it bonded but I have to assume it hasn't. I wish I could find out if it's already bonded someway without disassembling it.
    ---
    Edit:

    Check THIS out:
    [​IMG]
    Is it just me or is that saying you can bond ("connect together") neutral/ground through a twistlock receptacle? They assume you are using an appliance off of that outlet but still. It still acts the same as if I were to use a dummy plug in a twistlock 120v/240V receptacle and power the trailer from the 120V/15A ones. Although, it says "load side" which I guess would mean the appliance that is plugged in, not at the generator side?
     
    Last edited: Dec 21, 2007
  13. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Ground. A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth or to some conducting body that serves in place of the earth.

    As defined by the NEC ground means connected to earth. This term is misused by most people and is used out of place a lot of times.
    As I have pointed out the use of an earth connection is optional and if one is not established then there is no ground or grounding to be done.

    This is always a good idea to connect all electrical systems to earth but it is not necessary in a lot of cases. Take a transformer in a motor control center. A lot of these are not connected to earth.

    This is the place to connect the grounding electrode or the conductor that connects the generator to earth if you so choose to do so.

    No to connect this lug to the frame would be useless. Yes the neutral point needs to be connected to the frame.
    Although it might be a far piece to drive and cost a couple of dollars it is all about safety. Personally I wouldn’t think that you have the knowledge to take on this project yourself.

    No you can’t do a proper bonding through the twist lock receptacle.

    Anything between the generator (not the gasoline motor) and the first breaker, fuse or reset button on the generator is the line side. Any thing on the receptacle side of the first breaker, fuse or reset button on the generator is the load side. The bonding is required to be done on the line side of the generator or in the first breaker, fuse or reset button on the generator.
    Although this is not what the inside of your generator looks like here is where this generator is required to have the bonding take place. As can be seen the plate (terimnal bar) that the generator ground point is connect is bolted to the frame of the generator.

    I have shown you the proper way to achieve the required bonding and given you the NEC references to back up my statements. Each time I try to explain to you how to do this bonding in the most minimum safety standard allowed you come back with some way to try to jury rig the installation instead of the proper minimum standard.

    I don’t know anything more that I have to offer that can be more clear than what I have done short of giving you a few hours of study in the meaning of grounding and bonding which would be hard to do with someone that will not listen to what is presented to them in the first place.
     
    Last edited: Dec 22, 2007
  14. Cubey

    Cubey New Member

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    If I can gain access to the panel or whereever the terminal bar is located I can do it no problem I'm sure. The only thing I'm still slightly foggy on is if I bond the neutral to ground THEN to the frame because right now I think ground is isolated from the frame. As I understand it, they would have to be bonded together and then bonded to the frame for it to be with NEC code.

    Where is this typically located? In the panel where the outlets/breakers are? If I can find where it is, I can do it no problem I'm sure. I know how to do basic wiring (ie: installing an outlet, a light fixture, even creating a whole new DC 12V electrical system in an RV) but I'm just not up to speed on bonding/grounding/etc for AC power. If I can locate the terminal bar(s) in the generator, I'm sure will be able to bond them no problem.

    I was merely trying to find a secondary way to do it if it existed. I wasn't trying to find a less safe way really.
     
  15. Cubey

    Cubey New Member

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    Out of curiosity, how big and expensive is that generator that photo is of? Several photos I found of cheaper (but name brand) generators probably in the range of Coleman showing the inside of the panels and they made the generators with jumper wires on the receptacles, not on a terminal bar. If that is how this generator is made, jumpering the inside of the panel at the receptacles is going to be the same as using a plug-in dummy plug on the outside.

    Here are photos to illustrate:
    http://members.rennlist.org/warren/OriginalWiring.jpg
    http://members.rennlist.org/warren/portercable7500.jpg
    http://members.rennlist.org/warren/troybilt2.jpg
    All of those photos are how the generators were originally wired.

    If that is how this generator is, then a dummy plug would be just the same as using a jumper wire, don't you agree?
     
  16. jwelectric

    jwelectric Electrical Contractor/Instructor

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    I must disagree with you about this statement based on this statement.
    You most certainly do not understand the bonding of the neutral point of the generator.
     
  17. Cubey

    Cubey New Member

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    I managed to get the panel removed from the generator without removing the engine. It'll be tricky to get it back on but I'll worry about that when the time comes.

    Here is a high res photo of it pointing out a few details about it:
    http://ben.illiop.com/temp/coleman_panel.jpg

    Do you not agree that all I must do now is bond neutral to ground within this panel on one of the outlets (as pointed out in the photo) to make it bonded properly?

    That is how low end generators (ie: Briggs & Stratton) come from the factory when they are built bonded. A simple piece of 12 gauge wire between the ground and neutral terminals on the 120v/15A duplex will provide the necessary bonding.

    Take note of how they made neutral 12 gauge all the way to 120V/15A where as hot on 120V/15A is only 14 gauge. Looks like they wired it up so you could bond neutral/ground with a piece of wire and it would have the proper neutral gauge wire to handle it.
     
    Last edited: Dec 22, 2007
  18. jwelectric

    jwelectric Electrical Contractor/Instructor

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  19. Cubey

    Cubey New Member

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    What the? Now you are going against how generators are made at the factory as far as bonding??
     
  20. jwelectric

    jwelectric Electrical Contractor/Instructor

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    The bonding don’t take place at the receptacle it takes place as out lined in red

    Most generators that I have worked on has a place in the back of the generator to do the bonding.
    Should you do the bonding at the wrong place you will kill the PC board in the control panel.
    Seek help from your Coleman dealership.
     
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