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).]

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.

I do this and see no problem with it, I do install a grounding conductor between the enclosures.

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.

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.

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?

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)

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



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

Bob

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

Try telling that to some inspectors in my area

Bob,
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 I respect your opinion but I do not see that in ULs own book.


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

The link you provided says that one application is:


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,
I just don't see any applications listed that don't involve the use of a locknut. I would expect that UL only tests to the manufacturer's intended installation methods and that the method described here is not one of those methods. Lacking a statement from either UL or the manufacturer that this is an intended use of chase nipples, I would redtag this installation if I was the AHJ.
Don

Don


What code article would you cite?

To each their own, I would fight it.

Good talking with you.

Bob

Why not use a rigid metal nipple with locknuts & bushing instead of the coupling?

Al

Bob,
250.4(A)(3).
Don

You know, circumstances have dictated that I try this sort of connection a few times. I've hhad instances where the sheetmetal was so thin, or the receiving female threads were so shallow, that it was not possible to tighten the chase nipple enough to clamp down on the enclosure.
(In those cases, I instead used 'running thread.')

I usually go with a chase into an LB. I think it is much more sanitary inside the box than a nipple, locknut, and bushing. When I tighten the assembly up, it is mechanically very solid and the chase is in solid contact with the edge of the usually hole sawed hole.