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Thread: Bonding bushing without a locknut

  1. #1
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    Bonding bushing without a locknut

    Sometimes I can not properly fit a locknut and the required bonding bushing on the end of an EMT connector inside a junction box. There is not enough thread inside the box to hold both the locknut and the bushing. I'm using the standard thin locknut ( Type L-D) and bushing ( Type IBC-L-AC) from O-Z Gedney.

    Can the IBC-L-AC grounding insulated bushing be used to secure theaded conduit connectors in a knockout or slip hole?

    Thank you for your time.

  2. #2
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    Article 250.96,97 and 92(B)4 require bonding of raceways.If your using an approved bonding bushing, then that would meet the requirement. What are you doing that requires the use of bonding bushings and not plastic bushings?
    Rick

  3. #3
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    Use a bonding locknut and a plastic bushing.
    Instructor, Industry Advocate

  4. #4
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    Quote Originally Posted by Pierre C Belarge
    Use a bonding locknut and a plastic bushing.
    Pierre, This would not suffice if there were concentric knockouts, would it ?

    moonlight, I'm sure the answer might be different depending on AHJ's but 250.96 and 250.98 require bonding for "loosely joined metal raceways" and, in that light, your install might be compliant.

  5. #5
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    The UL "White book" for these bonding devices states they provide bonding means between conduit and box via set screws and/or bonding wire & terminal.

    A second locknut is neither necessary nor required. Get rid of it; especially if that extra locknut prevents the bonding bushing's listed set screw from making contact with threads.

    White book reference:

    GROUNDING AND BONDING
    EQUIPMENT (KDER)

    Grounding and Bonding Bushings — ..Grounding bushings for use with conduit fittings ..have provision for the connection of a bonding or grounding wire or have means for mounting a wire connector available from the manufacturer. Such a bushing may also have means (usually one or more set screws) for reliably bonding the bushing to the metal equipment enclosure or box in the same manner that this is accomplished by a bonding bushing. ...
    Roger Ramjet NoFixNoPay

  6. #6
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    Moonlite - welcome to the forum BTW - most inspectors would want it tight if anything, and often (for some reason) without the lock-nut the bushing alone would be loose in the can.... With the lock-nut - not enough threads on most connectors for the bushing to grap to...

    Have you ever tried putting the lock-nut outside the can, bushing tight inside? (Granted not wet location) :rolleyes:

    Either way steel connectors usually have more theads than a die cast would - try that.... And some bonding bushings are suitable as combination use as a lock-nut IMO - some aren't.... Most maluable steel would be.... Yours seems it would be...
    Electric heretic
    It's always gonna be in the last place you look....

  7. #7
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    The code allows raceways to be installed without a locknut if the bushing is not "wholly of insulating material".

    Check out the last paragraph of 300.4(G)

    Other options would be ordering different EMT fittings or looking for some really thin lock nuts.
    Last edited by iwire; 04-02-08 at 05:48 AM.

  8. #8
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    I install photovoltaic systems. The DC side of our systems are always above 250V. We also perform line side taps on the service entrances and once in awhile 480/277 grid-ties. As you know these require a bonding bushing on at least one end of the metal raceway.

    We also install GEC, grounding electrode conductors on every inverter, which then requires a bonding bushing on both ends of a metal raceway.

    So we install many, many bushings.

    I was just looking for some thing to say that I could use the bonding bushing to both bond the raceway and secure the race way at the same time. This particular bushing has threads deep enough to make a tight fit for the connector to the box, panel or inverter.

    Thanks for all your feedback! I'll look at the 300.4(G). I have to add... I work in CA, which just adopted the NEC 2005 in January '08.

  9. #9
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    Quote Originally Posted by iwire
    Check out the last paragraph of 300.4(G)
    ...in 2008 NEC.

    300.4(F) in 2005 NEC.

    I've used reducing washers between panel and grounding bushing before. Code compliant?

  10. #10
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    Quote Originally Posted by Smart $
    I've used reducing washers between panel and grounding bushing before. Code compliant?
    As a spacer? - good idea if so????

    Grounding bushing YES - Grounding lock-nut - NO!
    Electric heretic
    It's always gonna be in the last place you look....

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