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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    Aug 10, 2007
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    Southern Arkansas
    No, it is not an RV-listed genset. It is a Coleman. However I will be operating the generator about 25-50 feet away from the trailer, not "installing" it into a compartment.
     
  2. Cubey

    Cubey New Member

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    Aug 10, 2007
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    Southern Arkansas
    Hm, new question but still completely related.

    Should the chassis of an RV be connected to ground of the 120v powering it (grid or generator) or should ground be isolated from the chassis.

    There seems to be two difference scenarios and therefore two different rules.

    1: If using an external portable generator, ground should not be connected to the chassis of the RV/vehicle. (NEC does does not say you must)

    2: If using a vehicle mounted generator, you must connect the ground to the chassis. (NEC code says you must).

    So would I be safe and correct if my trailer has ground isolated from the chassis?
     
  3. jwelectric

    jwelectric Electrical Contractor/Instructor

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    No!!!!!
    This is cleared up in the 2008 code cycle by making the statement in 51.47(R)(4)
    ONLY INSTALL A GENERATOR LISTED
    SPECIFICALLY FOR RV USE
    GENERATOR CIRCUIT. THIS CONNECTION
    IS FOR GENERATORS RATED 110–125-VOLT AC,
    60 HZ, ______ AMPERES MAXIMUM.
    or
    ONLY INSTALL A GENERATOR LISTED
    SPECIFICALLY FOR RV USE
    GENERATOR CIRCUIT. THIS CONNECTION
    IS FOR GENERATORS RATED 120/240-VOLT AC,
    60 HZ, _______ AMPERES MAXIMUM

    Any generator used MUST be bonded to the RV. The panel in the RV MUST be bonded to the frame of the RV
     
  4. Cubey

    Cubey New Member

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    Southern Arkansas
    Where did you find that NEC code 51.47(R)(4)? I can't find *any* mention of it on MilkeHolt.com or in Google at all.

    Technically I'm not "installing" such as in a compartment meant for an RV generator or luggage. That may be what NEC code refers to as some folks think it is okay to use a propped open luggage compartment as a means of "installing" a portable generator.

    If NEC means you can no longer use any generator that isn't made specifically for RVs, then there is going to be thousands upon thousands of people purposing ignoring NEC code (probably myself included!) all around the country because that just doesn't make sense that you can't use an outdoor generator in a safe fashion (placed at least 25 feet away) to power an RV that has it's bondings done correctly.

    About bonding: As I understand it, neutral and ground in the RV's breaker panel should *not* be bonded (since is basically a sub panel) but ground on the panel *should* be bonded to the chassis, regardless of using grid or generator power.
    --
    Edit: I was mistaken about my trailer not having ground bonded to the chassis. I found where the bare ground comes out and connects to the chassis near the electrical input so it *is* bonded as it should be (ground/chassis is bonded, neutral/ground is not). It should be perfectly safe and up to current NEC code to operate a generator for my trailer, assuming NEC hasn't made it so that you can never use a portable generator to power an RV. That does not make any sense to me if that is the case.
     
    Last edited: Nov 13, 2007
  5. jwelectric

    jwelectric Electrical Contractor/Instructor

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    This is from the 2008 code cycle.
     
  6. Cubey

    Cubey New Member

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    I finally found it. You posted it as 51.47(R)(4) instead of 551.47(R)(4)

    Also you misquoted it/misunderstood it. What you pasted is what is meant to be printed on a label and attached to RVs in compartments meant for RV generators only. That is not an actual NEC code per say, it is only a label that is required by NEC code for RVs with generator compartments.

    I found it in this document:
    http://www.nfpa.org/assets/files/PDF/ROP/NEC2008Article550-647.pdf

    That is why there is a blank section in it. It is a label with a form field so they can enter in the correct max amps depending on the electrical system equipped on the RV the label is being attached to.

    The NEC code is not banning portable generators from RV use, it is merely revising the label warning about not installing portable generators into generator compartments built into RVs.
     
    Last edited: Nov 13, 2007
  7. jwelectric

    jwelectric Electrical Contractor/Instructor

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    www.nfpa.org

    Try this link. http://www.nfpa.org/freecodes/free_access_agreement.asp?id=7008SB

    You will be required to join in order to see the version
     
    Last edited: Nov 13, 2007
  8. Cubey

    Cubey New Member

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  9. Cubey

    Cubey New Member

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    Southern Arkansas
    I am reading the document now. Code 551.47(4) has to do with RVs with 50A power service and the bit you pasted before is a label as I previously mentioned. Oddly enough, the 2008 code 551.47(4)(D) which should be the final, official version of the revised label 551.47(R)(4) that you mentioned is different. But basically what you pasted is not the NEC code banning use of portable generators with RVs, it only bans sticking one into an RV's generator compartment which unfortunately isn't common sense for some folks.

    Section 250.34 of the 2008 code is pretty much the same about grounding and usage of portable generators.

    Section 551.30 (Section III - Other power sources) pretty much is referring to "vehicle-mounted" generators for the most part when it discusses ventilation and compartments.

    No where in the NEC for 2008, as far as I can find, has portable generators been banned for use with RVs. They are just revising the warning label telling folks not to kill themselves by sticking a portable generator in their "vehicle-mounted" generator compartment.
     
  10. Cubey

    Cubey New Member

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    Aug 10, 2007
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    Southern Arkansas
    Check out the emails between Coleman Powermate support and I:

    ---

    Q: Hello. I am a bit confused about grounding issues concerning portable
    outdoor generators. The manual states that you must follow NEC code
    (250.34) and drive a grounding rod for portable generators. However,
    actual NEC code 250.34 (A) Portable Generators, says you do NOT have to
    use a "grounding electrode" (grounding rod). So does the Coleman manual
    for generators override what NEC code says or is it just that the manual
    is mistake about what NEC code says? OSHA also states you do not have to
    ground a portable generator. Here are a few links pointing this out:
    http://www.mikeholt.com/mojonewsarchive/GB-HTML/HTML/NECArticle250Sections250.20-250.34~20020124.htm
    http://www.osha.gov/OshDoc/data_Hurricane_Facts/grounding_port_generator.pdf
    Thank you.

    A: We recommend grounding the generator whenever it is in use.


    Q: You may recommend it but do you consider it a requirement? And why does the Coleman manual misquote/"lie" about NEC code requiring a ground rod when it doesn't? This is assuming that local city codes won't require it
    beyond the NEC code.

    A: The metal parts of generator and the grounding terminals of the
    receptacles are not bonded to the generator frame, which requires the
    generator to be grounded.

    It is not absolutely necessary for the generator to be grounded for it
    to produce power, but it is a safety feature that will prevent
    accidental shock.


    Q: In that case, all one must do is bond the receptacles to the frame with
    the proper gauge wire, correct?

    A: Yes, it's possible.

    --

    The support guy from Coleman just admitted that if you bond the ground from the generator's receptacles to the frame manually you would not have to use a ground rod. So if your generator happens to be one already bonded in such a way you wouldn't have to do it, otherwise you would have to do it manually to avoid using a ground rod to follow the manufacturer's instructions and NEC code.
     
    Last edited: Nov 14, 2007
  11. BrianJohn

    BrianJohn DIY Senior Member

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    Location:
    VA
    Not that the support guy knows anything about grounding..but if you happen to talk to him again ask him HOW A GROUND ROD PREVENTS SOMEONE FROM A SHOCK.
     
  12. Cubey

    Cubey New Member

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    Southern Arkansas
    I did just that. I replied saying:

    "Out of curiosity, how does a ground rod on a stock Coleman Generator
    (without receptacle ground bonded to the frame) prevent someone from
    being shocked?"


    His reply was:

    "It's mostly to prevent an accidental shock it the machine would happen
    to get wet. Instead of the electricity traveling through the frame it
    would travel out through the ground. "
     
  13. BrianJohn

    BrianJohn DIY Senior Member

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    Jun 22, 2007
    Location:
    VA
    "It's mostly to prevent an accidental shock it the machine would happen
    to get wet. Instead of the electricity traveling through the frame it
    would travel out through the ground."


    Send them this.

    Are you out of your ever loving mind! If the electricity travels THROUGH the ground (which by the way is a less than a fair conductor) where is it going too!

    Mother Earth is the harbinger of a lot of things but she could care less if a Coleman generator exist and/or much less if is connected to her backside by means of a STICK IN THE EARTH.

    In a short of an energized conductor the the voltage is going to return to it's source, generally by the path of least resistance, though any viable paths may share some of the fault current. We call it a circuit because it is CIRCULAR starts and ends in the generator.


    from Wikipedia

    An electrical circuit is a network that has a closed loop, giving a return path for the current. A network is a connection of two or more components, and may not necessarily be a circuit.

    Oh well hopfully you have your answer to the original post and Coleman is much bigger than me they will continue to do what they do and many if not most electricians, inspectoers and end users will continue to drive ground rods, which in it's self is not bad*, but unecssary

    *Unless you hit a high voltage underground cable.
     
  14. 480sparky

    480sparky In the Trades

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    Electrical Contractor

    I wound then ask, "To where?......" It isn't like a bucket of popcorn that can spill out and make a mess. Electron flow is not affected much by gravity.

    Electricity needs a compete circuit in order to flow. If there's a short-circuit in the unit itself, and it is properly bonded and grounded within itself, then the breaker will open.
     
  15. BrianJohn

    BrianJohn DIY Senior Member

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    Jun 22, 2007
    Location:
    VA
    Sparky you know durn well that the earth is a gigantic bucket for electrons just waiting to suck up the extra/spare electrons from our wiring errors.
     
  16. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Retired Systems engineer for defense industry.
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    New England
    Having spent some time in the military, grounding things became a big hassle. We often had multiple things connected to separate generators, maybe stuck on top of a mountain, where you couldn't really drive a ground stake. That took some real effort to keep from getting yourself knocked on your butt sometimes. Often it was just to ensure you could drain off a significant static buildup.

    FOr a single generator on a single device, a ground rod probably isn't that big of a deal. When you are trying to establish ground planes for things like communications or radar sets, it becomes much more problematic. In the desert, the cooks would order lots of extra salt, and salt down then keep moist the ground rods/cables in order to have a phone or radio system work properly. Sand is a lousy conductor, so a ground rod(s) or burried array of cables often wouldn't work well.

    This was more for noise and ground plane, not for safety, although that did come into play as well. It also helped with near (but not direct) lightning strikes.

    I wouldn't worry about grounding a generator on an RV. Then again, I don't have one nor am I a licensed electrician:).
     
  17. Cubey

    Cubey New Member

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    Aug 10, 2007
    Location:
    Southern Arkansas
    Not much point in asking them anything else. They already admitted that in some cases they don't think you have to drive a rod if the ground in the receptacle is bonded to the generator's frame. A short piece of 12 gauge wire added on would correct this anyway and make it compliant to not needing a ground rod (according to the Coleman support guy anyway).

    If in doubt of it already being bonded, I could do it anyway though that could possibly cause a ground loop if it already has ground bonded to the frame but thats about the only risk in adding it. I am already familiar with installing receptacles, switches, light fixtures, etc so routing ground to frame will be no problem at all.

    I assume the breaker you refer to are the ones at the trailer's panel.

    Going back to a question I asked a bit ago, since I don't think I got an answer or I forgot it and can't find where it answered, should neutral be bonded to ground/frame at the generator? I know it shouldn't be at the trailer's panel. Might be good to play it safe and manually bond neutral to ground just to be safe if it is supposed to be that way.
     
    Last edited: Nov 15, 2007
  18. 480sparky

    480sparky In the Trades

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    Electrical Contractor
    From a portable genny? :confused: How do you complete the circuit?

    The earth may be capable of 'sucking up' all those electrons that trickle off by screwdriver or I spill out of my pouch, but then how do they get back to the generator?
     
  19. BrianJohn

    BrianJohn DIY Senior Member

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    Jun 22, 2007
    Location:
    VA
    it is FM F***ING MAGIC
     
  20. jwelectric

    jwelectric Electrical Contractor/Instructor

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    Occupation:
    Instructor
    Location:
    North Carolina
    If the neutral point of the generator is not bonded to the equipment grounding conductors supplied by the generator then the overcurrent device will not operate properly.

    We know that the grounded (neutral) must be isolated from the equipment grounding conductors in the distribution panelboard inside the RV as outlined below;
    551.45 Distribution Panelboard.
    (A) Listed and Appropriately Rated. A listed and appropriately rated distribution panelboard or other equipment specifically listed for this purpose shall be used. The grounded conductor termination bar shall be insulated from the enclosure as provided in 551.54(C). An equipment grounding terminal bar shall be attached inside the metal enclosure of the panelboard.

    The lack of bonding the equipment grounding conductors to the grounded (neutral) conductor in the panel inside the RV makes the generator a separately derived system and must be treated thus.

    The equipment grounding conductors do not bond in the panel inside the RV so any fault to any metal including the shell of the unit could not return through a path of low-impedance and if the equipment grounding conductors don’t bond to the grounded (neutral) at the generator either then there is a problem.

    By bonding the generator the low-impedance path is established and now any and all of the overcurrent devices can function as they were designed.

    The driving of a ground rod will play no role in the operation of any overcurrent device and will only protect the generator in the event of lightning, line surges, or unintentional contact with higher-voltage lines. I can’t see either of the latter two taking place if the same cord is used to supply the RV being used from either the generator or the pedestal.
     
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