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#89887 - 10/23/04 10:23 AM Connection between panels
George Little Offline
Member
Registered: 01/18/04
Posts: 1488
Loc: Michigan USA
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).]
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George Little
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#89888 - 10/23/04 10:53 AM Re: Connection between panels
Ryan_J Offline
Moderator
Registered: 08/19/03
Posts: 1374
Loc: West Jordan, Utah, USA
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.
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Salt Lake City
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#89889 - 10/23/04 02:40 PM Re: Connection between panels
iwire Offline
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Registered: 01/05/03
Posts: 4391
Loc: North Attleboro, MA USA
I do this and see no problem with it, I do install a grounding conductor between the enclosures.
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Bob Badger
Construction & Maintenance Electrician
Massachusetts
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#89890 - 10/23/04 08:42 PM Re: Connection between panels
BigB Offline
Member
Registered: 03/31/04
Posts: 719
Loc: Tucson, AZ USA
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.
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#89891 - 10/23/04 08:55 PM Re: Connection between panels
BigB Offline
Member
Registered: 03/31/04
Posts: 719
Loc: Tucson, AZ USA
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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#89892 - 10/23/04 09:54 PM Re: Connection between panels
gfretwell Offline


Member
Registered: 07/20/04
Posts: 9039
Loc: Estero,Fl,usa
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?
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#89893 - 10/24/04 03:22 AM Re: Connection between panels
iwire Offline
Moderator
Registered: 01/05/03
Posts: 4391
Loc: North Attleboro, MA USA
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.

Bob

[This message has been edited by iwire (edited 10-24-2004).]
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Bob Badger
Construction & Maintenance Electrician
Massachusetts
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#89894 - 10/24/04 07:28 AM Re: Connection between panels
dmattox Offline
Member
Registered: 10/20/04
Posts: 265
Loc: Anaheim, CA
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
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#89895 - 10/24/04 09:36 AM Re: Connection between panels
resqcapt19 Offline
Member
Registered: 11/10/00
Posts: 2148
Loc: IL
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
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#89896 - 10/24/04 10:04 AM Re: Connection between panels
iwire Offline
Moderator
Registered: 01/05/03
Posts: 4391
Loc: North Attleboro, MA USA
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
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Bob Badger
Construction & Maintenance Electrician
Massachusetts
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