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#89887 10/23/04 01:23 PM
Joined: Jan 2004
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I wonder what this group would think about an installation that would have us tying two panels together with a rigid metal coupling and two metal chase nipples? No lock nuts are used and the voltage to ground is less than 250v. Neither of these panel are service equipment or being used in a classified area,

[This message has been edited by George Little (edited 10-23-2004).]


George Little
2017 / 2014 NEC & Related Books and Study Guides
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I see this type of installation every day, it works great. I also think it would make a good fault clearing path, considering the threaded connections. [Linked Image]


Ryan Jackson,
Salt Lake City
Joined: Jan 2003
Posts: 4,391
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I do this and see no problem with it, I do install a grounding conductor between the enclosures.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Joined: Mar 2004
Posts: 785
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Our inspectors do not allow the chase nipples alone for bonding as they don't dig into the metal like a locknut. If we use chase nipples we must also run a bonding jumper.

Joined: Mar 2004
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Actually, to add to my post, I've never used 2 chase nipples between panels. I've use one chase nipple to an LB, where our inspectors require a bonding wire to the j box. This would bond the j box and pipe and LB up to the panel. With two chase nipples as stated, a bonding wire would only bond the panels and, if there was poor contact at the chase nipples to the panels, the coupling and chase nipples could concievably become energized with no grounding path.

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Run a locknut down in the chase nipple with the teeth out then screw it through the can into the coupler?
If the threads are long enough to do this you should get a good bite on the can. If not, How about a big star washer?


Greg Fretwell
Joined: Jan 2003
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Guys chase nipples do not have to be treated differently then any other raceway fittings.

Chase nipples, like most other raceway fittings are UL listed for grounding.


2003 UL White Book
CONDUIT FITTINGS (DWTT)
Quote
GROUNDING

All metal fittings for metal cable, conduit and tubing are considered suitable for grounding for use in circuits over and under 250 V and where installed in accordance with the NEC, except as noted for flexible metal conduit fittings and liquid-tight flexible metal conduit fittings.

If there is paint in the way of a good connection you must follow 250.12

Quote
250.12 Clean Surfaces.
Nonconductive coatings (such as paint, lacquer, and enamel) on equipment to be grounded shall be removed from threads and other contact surfaces to ensure good electrical continuity or be connected by means of fittings designed so as to make such removal unnecessary.


Run bonding jumpers if you like but do not let anyone tell you that it is required. [Linked Image]

Bob

[This message has been edited by iwire (edited 10-24-2004).]


Bob Badger
Construction & Maintenance Electrician
Massachusetts
Joined: Oct 2004
Posts: 265
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Quote
Run bonding jumpers if you like but do not let anyone tell you that it is required.

Try telling that to some inspectors in my area [Linked Image]

Joined: Nov 2000
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Bob,
Quote
Chase nipples, like most other raceway fittings are UL listed for grounding.
I'd be very surprised if UL actually tested chase nipples installed in the manner described in this post. I do not believe that chase nipples threaded into couplings or fittings are a suitable fault return path. I believe that the intended installation requires the use of a locknut.
Don


Don(resqcapt19)
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Don I respect your opinion but I do not see that in ULs own book.

Quote
All metal fittings for metal cable, conduit and tubing are considered suitable for grounding for use

I have never seen anything that says chase nipples must be used with locknuts.

The link you provided says that one application is:

Quote
To couple boxes back-to-back.

That would only place a locknut in contact with one enclosure.

The way I read 250.12 a locknut would be the "fitting designed so as to make such removal unnecessary"

If there is no locknut as on one side of a chase nipple, then paint removal becomes necessary.

Truthfully IMHO, it is a stretch to believe that the contact made between the straight cut threads of the chase nipple and a coupling, if made up wrench tight, would not provide an equal or better fault path as a die cast set screw EMT connector or coupling.

The only exception I would make to that statement would be for service conductors and the code requires bonding of all raceways in that application.

JMO, Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts
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