Home Generator.

Discussion in 'General Electronics Chat' started by heatshrink, Oct 22, 2010.

  1. heatshrink

    Thread Starter New Member

    Oct 22, 2010
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    I bought a portable 7000 watt continuous duty generator. It has a floating neutral. I bought a 4 prong L14-30p plug and was going to wire it to the existing underground wire running from a shed where the generator will be to the house. There is a junction box on the outside of the house where the underground wire will be connected to a 8/3 wire with a ground. From there the 8/3 will go to a 200amp manual transfer switch. Whereby when in the up position I'm on pole power, in the middle no power to the house period and in the down position I'll be on generator power. The problem I have is that the buried under ground cable is only 3 conductor, period, no ground. Can I get around this safely or do I need to bury another cable? Any help would be appreciated. Thanks
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Where are you ? In the US, all home wiring is grounded, even homes built >90 years ago. Check your service entrance. There may be a ground there that you missed.

    John
     
  3. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    If it were me I would just run a separate buried ground wire between the MBT switch ground and the generator ground. http://stormgrounding.electrical-in...ng-wire.html?gclid=CKON1YTK56QCFQQ-bAodjDow1Q
     
  4. heatshrink

    Thread Starter New Member

    Oct 22, 2010
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    On the outside of the generator there is a lug to attach a ground wire and Honeywell recommends attaching it to a ground rod. Because of the floating neutral I surmise. I get all of that. Can I safely use the 3 conductor to get power to the house?
     
  5. heatshrink

    Thread Starter New Member

    Oct 22, 2010
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    This is a portable generator so is the extra wire needed in a situation like mine where I'm tying into a well grounded service panel?
     
  6. nsaspook

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    Aug 27, 2009
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    Ground rod requirements.
    NEC code section 250.30, 250.34:
    http://www.mikeholt.com/mojonewsarchive/GB-HTML/HTML/NECArticle250Sections250.20-250.34~20020124.htm

    http://www.google.com/url?sa=t&sour...GqbQe9ucAMElxdKdw&sig2=iCtiUNBS8V4D7WmNN3q6rQ
     
    Last edited: Oct 23, 2010
  7. marshallf3

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    Jul 26, 2010
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    Just use the three wires - two phases plus the neutral. The house should already have a ground rod somewhere (or a cold water pipe ground) but I'd double check it and if not I'd install one. Rule #1 in electrical is never assume, I've moved into houses only 30 years old that had absolutely no grounding system at all, just the grounds of the outlets bonded to the neutrals in the breaker box.

    250.34 may state that you don't need to due to the plug, but I feel it's best to drive a ground rod deep into the soil near the generator and ground the generator's frame or ground lug to that using the proper size and type of clamp for a ground rod.

    You'll want a true ground rod for electrical, they're around 8' long and it takes a lot of hammering to get them into the ground. You can find shorter ones but those are not to code, they're really only used for antenna systems and serve more as a false sense of protection only being 4' long anyway.

    Some people make up a deal with a piece of pipe that will fit over the rod and put a heavy weight on the closed end then use it like a slide hammer, others use an SDS-type hammer drill but DO NOT set it to rotate, only to hammer.

    Then there's people like me that stand on a ladder and use a 4 lb sledge.
     
    Last edited: Oct 22, 2010
  8. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    with the floating neutral portable, you will be using a 2 pole transfer switch with the neutral securely connected to system neutral. That satisfies the 'ground' aspect. However, by code, you must run a bonding conductor with your power cables, requiring your fourth wire.
     
  9. nsaspook

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    Aug 27, 2009
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    That's how I see it also. For a non-SDS (does not switch neutral) system it must be bonded with a ground wire and not have a separate non-bonded grounding system.

     
  10. heatshrink

    Thread Starter New Member

    Oct 22, 2010
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    Thanks for the info. Sounds like I need a 4th wire to be proper. Thanks again.
     
  11. heatshrink

    Thread Starter New Member

    Oct 22, 2010
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    I know you thought this thread was dead but I was fixing to buy a 4 wire to replace the already buried 3 wire when it dawned on me. Why not use the ground wire coming off of the light circuit? Can I run a jumper from the generator ground on the L14-30P plug to the light circuit ground? They all go back and tie together at the service panel ground bar. Would save me a chunk of change and time.
     
  12. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    Code says NO
     
  13. marshallf3

    Well-Known Member

    Jul 26, 2010
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    The code makes little sense to me, must have something to do with the transfer switch being in there.

    Does your light power feed come into a proper breaker box in the outbuilding?
     
  14. GetDeviceInfo

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    Jun 7, 2009
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    OP, think 'insurance'.
     
  15. heatshrink

    Thread Starter New Member

    Oct 22, 2010
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    The light circuit power comes from the main breaker panel box, the only one I have for the entire house. Excluding the main service panel. All green ground wires run back to and tie to the ground bar in the main breaker panel box. Code says no, okay,but please explain how and why it's unsafe? Don't all shorts/ground faults run back to the breaker panel and main ground? How will using the ground wire in the light circuit as a grounding wire for the generator be harmful?
     
  16. heatshrink

    Thread Starter New Member

    Oct 22, 2010
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    Another thing in my 2 pole manual switch box the neutral wire is not switched just the 2 hot legs. When in the up position I'm running on generator power, in the middle postion no power period, in the down position I'm on utiltity power. The neutral and ground are always connected no matter what position the level is in. When I'm on utility power the neutral and ground wire are still connected with a path back to the generator. So how does using a light circuit green ground make any difference other than it ain't code?
     
  17. shortbus

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    Sep 30, 2009
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    When I had my unattached workshop/garage rewired in 2001 they ran four wires to it, 2 hot, 1 neutral and 1 ground. The original had 2 hot and 1 neutral and a ground rod at the shop. When the new service was put in they disconnected the ground rod at the shop. The electrician said that was the new code but didn't have an explanation!

    The ground wire in your light circuit is probably not big enough gage for the amps. Ground wire is sometimes one gage smaller than the hot and neutral in romex style wire.
     
  18. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    your neutral is not a ground, although it is tied to ground at the service entrance. If you have a hot to housing short out in the shed, what protects you from electrocution. Code calls for the bonding of all metalic equipment to ground, to prevent a build up of voltage potential.

    Code calls for a bonding conductor sized from a chart, based on the ampacity of the largest current carrying wire in the group, and that the bonding conductor accompany the cable group. Why, because accident investigations show it's in good measure.

    Such an installation would require a permit. Why, because it's mandated for the safety of the public at large.
     
  19. shortbus

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    Sep 30, 2009
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    I understand this, what I don't understand is the not using more than one ground rod. Why is a second ground rod now outlawed?
     
  20. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    multiple ground rods are used in some situations and again guided by code, must be interconnected as specified.

    In regards to 'ground', there is only one ground wire. It runs from your neutral bar to an earthing electrode, on the service side of your main disconnect. Actually, there is a second ground, and it is at the step down transformer of the utility supply. Additional supplies, must also be grounded at the source.

    Within your branch circuits, there is no grounding allowed. However, as mentioned, all metallic components must be 'bonded' to the earthing electrode in a controlled fashion.

    The neutral (or hots) is intended to carry ALL returning current. Any current seeking ground does so at a potential, and between service ground and a remote ground, that potential can be high. Hence the 'bonding' requirement.

    There are cases where a 'floating ground' is implemented. Generator modules used in rig service can have multiple grounding rods to reduce 'step potential'.
     
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