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  1. #1
    Robert Ehlers's Avatar
    Robert Ehlers Guest

    Default Confused UFER situation

    First of all I know that there are a lot of posts on this topic, but I can't quite figure it out. I am building a detached garage with a 125a sub panel. The electrical is as follows. The main power (service) feeds a meter pole outside of my mobile home. That panel under the meter is a 200amp. It feeds a 4 wire sub panel in my mobile home. There is a ground rod in the ground outside next to that meter pole. The detached garage has a 2" pvc pipe going from the outside 200amp panel to the garages 125amp sub panel. There is also a UFER stub at the outside of the garage where the panel is.
    I ran H H N G to the garage from the main 200a meter pole panel. I was told that the UFER of the garage is supposed to be connected to the main 200amp panels ground. After having an inspection the other day, He told me that the UFER is supposed to be connected to the garage panel ground, not the main 200amp panel. Since the UFER is stubbed outside of the garage and not stubbed inside the garage, Is it OK to have a 5th wire (8 gauge) inside the 2" pipe to attach the UFER to the garage panels ground via the 5th wire? I assume I would have to use a floating ground bar to make the junction inside the 200amp panel. Or do I have to unbury the UFER going to the 200amp panel and bring it into the garage by drilling through the outside wall?
    Also on a side note, is there something written in the code that says I have to staple NM romex 2' minimum? I stapled it every 12" to be neat and clean, and he said there were "TOO MANY" staples. SO I have to pull half of them out. Please help, sorry for the confusion.

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  2. #2
    Richard Moore's Avatar
    Richard Moore Guest

    Default Re: Confused UFER situation

    Also on a side note, is there something written in the code that says I have to staple NM romex 2' minimum? I stapled it every 12" to be neat and clean, and he said there were "TOO MANY" staples. SO I have to pull half of them out.
    Let's do that one first as it's easy. NM cable is supposed to be secured (staple, straps, etc, etc) at at intervals not exceeding 4½ feet. There is no minimum interval code that I am aware of. Every 12" does seem a little...umm...anal (scooz me) but that's not the same as "too many". I'd ask him to show you the local "code" on that one because I'm pretty sure a national "too many staples" code doesn't exist.

    On the UFER and remote building situation:
    This does get a little tricky and there are some exceptions but as you already have a four wire feed we will stick to that.

    Basically, the "G" in your HHNG feed is there to handle ground faults by passing the fault current back to the service equipment and from there to the utility grounded conductor. This path will reliably allow the circuit breakers to trip. The main purpose of the garage UFER is to handle lightning strikes by providing an easy path to the earth for that very high current, hopefully preventing it from energizing anything or everything else.

    All of your 4 wire feed from the 200-amp service panel should have gone directly to the garage panel which should have the grounds and neutrals separated and the neutral bar should float (in other words...normal sub-panel wiring). A separate grounding electrode conductor should then be run from the garage panel grounding bar as directly as possible to the UFER.

    See these two illustrations at Mike Holt's forum...
    MikeHolt.com
    MikeHolt.com


    Is it OK to have a 5th wire (8 gauge) inside the 2" pipe to attach the UFER to the garage panels ground via the 5th wire? I assume I would have to use a floating ground bar to make the junction inside the 200amp panel.
    No! That would be a bad idea. A lightning strike might have to travel from the garage panel to the service panel and back again all within the pvc conduit. That sounds like it would get very, very hot if it worked at all!

    Last edited by Richard Moore; 06-08-2008 at 11:58 PM.

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