This section states that"the locknut bushing and double locknut types of contacts shall not be depended on for grounding purposes, but bonding jumpers with proper fittings or other approved means of bonding shall be used"
This section also refers to 250.100 which then leads to 250.92B 2 thru 4
250.92b2 states connections utilizing threaded couplings or threaded hubs made up wrench tight will ensure bonding.

So if I have a rmc conduit that starts at a trough, typical double locknut, ends at a threaded hub in the C1D1 zone made up wrench tight, pull in an EGC into the box with the threaded hub, land the EGC, am I depending on the double lock nut to bond the pipe or is the conduit bonded via the threaded hub??

Hello Walrus,

Seems to me that the double locknut is fine for considering the conduit bonded. Since the trough is not in the C1D1 zone.
Looks like 250.100 & 250.92 (B) 2 permits the installation as described.

*Disclaimer*
Just an opinion from an electrician, and not an inspector. Felt I should put that in considering that this site is also available to the average 'Joe'.

Luke

Luke,
It doesn't matter that the trough is not in the classified area. 502.30(A) requires service type all the way back to the service disconnet or the source of a separately derived system.
Don

walrus,
Yes, you are depending on the double locknuts. 501.30(A) says in part: "Such means of bonding shall apply to all intervening raceways, fittings, boxes, enclosures, and so forth between Class I locations and the point of grounding for service equipment or point of grounding of a separately derived system."
You need a bonding bushing at the trough, and on back to the service or SDS.
Don

Don
Thanks for the reply, I was hoping you'd weigh in.
Heres the thing I don't understand, 250.100 says if you are using a threaded hub you have effective bonding. At the C1D1 area you will have a threaded hub, I land the EGC at that hub, so why isn't the conduit bonded back to the trough?? Its that word "depend" that opens it up to question IMHO.

Let me use another example, I use the exception that allows me to use PVC in between the trough and C1D1 area, stopping 2 feet before I go into the C1D1 area. Because I used PVC I have to use an EGC, I land it in the box with the threaded hub, that 2 feet of RMC is now bonded, correct?? If that 2 feet is bonded why isn't 100(or 10 or 50 etc) feet of RMC bonded

Walrus,
I don't know why, but the code requires the use of service type bonding at each connection point.
Don

GEORGIA NEC 2011:
I have 24VDC SOLENOID VALVES IN A CID2 AREA
THE WIRING IS IN A WIREWAY (TROUGH) IN NON-HAZ AREA

STARTING AT THE WIREWAY, DO WE INSTALL A GROUNDING BUSHING WIRED TO A COMMON GROUND CABLE IN W/W, THEN RMC CONDUIT TO A FORM 7 CONDUIT BODY, THEN A FLEX, (LISTED, GROUNDING TYPE) TO THE SOLENOID THREADED HUB; SPLICE THE 2 LEADS TO THE FIELD WIRE IN THE FORM 7; ALL FITTINGS LISTED FOR GROUNDING ? DO WE NEED AN EXT. BONDING JUMPER ON THE FLEX?

WILL THIS ALSO NEED A EGC FROM THE FORM 7 TO WHERE ?

WDG...

All capitals is brutal to read...

Your post deserves its own heading.

WRT all of the above, the bonding is 'belt and suspenders' in hazardous areas -- all the way through. The issue is sparking and inductive chokes.

For such bonding runs, the EGC is treated like it was a section of the GEC -- which, as we all know, requires bonding bushings at every possible choke point. ( See the NEC Handbooks -- any recent year will do: 2011,2008,2005,2002,1999....)

24VDC doesn't tell me that it's an arc proof design element. Perhaps it's backed up by lead-acid cells. 24VDC can throw an arc -- the typical arc welder runs at 28 to 32 Volts!

LOL!!!

I have to agree with Tesla...
All Caps is the Bulletin Board equivalent to Yelling.

--Scott (EE)