Bonding in Class II Div 1

[Richard S]

This is a 2 part Bonding in Class II Div 1 environments question.

1st - When using LFMC (less than 6') to connect to equipment as allowed per 502.10(A)2 & (B)2, and there is an equipment grounding conductor (EGC) installed within the raceway, is there a need to install and external equipment bonding jumper? I believe that 502.30(B) requires a bonding jumper per 250.102 and that 250.102(E)(1) allows for the bonding jumper to be installed inside the raceway. Can the EGC installed within raceway serve as both EGC and bonding jumper?

2nd - 250.100 requires bonding of raceways per 250.92(B)(2)-(B)(4). 250.92(B)(3) lists threadless coupling and connectors if made tight for metal raceways and metal-clad cables. Would this apply to LFMC connectors? I associate threadless couplings and connectors with either compression or set screw fittings for Rigid or EMT. Would this apply to LFMC? For example, if LFMC connector was used to connect to and enclosure (without concentric ko's) outside of Class II Div 1 areas, would this be a sufficient connection for electrical continuity or would another listed device (bonding bushing or locknut) per 250.92(B)(4) be required?

Thank you for your replies.

 

[rbalex]

1st - ...Can the EGC installed within raceway serve as both EGC and bonding jumper?

2nd - 250.100 requires bonding of raceways per 250.92(B)(2)-(B)(4). 250.92(B)(3) lists threadless coupling and connectors if made tight for metal raceways and metal-clad cables. Would this apply to LFMC connectors? I associate threadless couplings and connectors with either compression or set screw fittings for Rigid or EMT. Would this apply to LFMC? For example, if LFMC connector was used to connect to and enclosure (without concentric ko's) outside of Class II Div 1 areas, would this be a sufficient connection for electrical continuity or would another listed device (bonding bushing or locknut) per 250.92(B)(4) be required?

Thank you for your replies.

1. Technically, yes although several CMP14 members would prefer that an internal EGC be limited to a connection between two enclosures that were also directly connected by the LFMC.

2a. Threaded methods are preferred. "Liquidtight flexible metal conduit with listed fittings" pretty much demands that. [Section 502.10 (A)(2)(2)]
2b. While you have to combine the 502.30(A) main text and its Exception to arrive there, outside the classified location, bonding may be achieved by virtually an recognized means.

Basically, grounding/bonding requirements in any classified location are identical regardless of Class, Division or Zone.

 

[Richard S]

2b. While you have to combine the 502.30(A) main text and its Exception to arrive there, outside the classified location, bonding may be achieved by virtually an recognized means.

Thank you for your detailed reply Mr. Alexander. I get your relies to 1 and 2a, but I am struggling with 2b. I've read 503.30(A) main text, its exception and the commentary (2011 Handbook) multiple times and still need a little more clarification. The way I read it is that the locknut-bushing and double locknut type of contact is not allowed all the way to the source (in this case a separately derived system). (A) Bonding. The locknut-bushing and double-locknuttypes of contact shall not be depended on for bonding purposes, but bonding jumpers with proper fittings or other approved means of bonding shall be used. Such means of bonding shall apply to all intervening raceways, fittings, boxes, enclosures, and so forth, between Class II locations and the point of grounding for service equipment or point of grounding of a separately derived system.

Perhaps a couple of pictures will help. These are from small transformers that are installed outside of the classified area that feed circuits within the classified area. These are the sources of our separately derived system where bonding methods are in question. There are disconnect switches on the load side of of these transformers that are not shown in the pictures.

The pictures shows connections to the transformer. One with LFMC with listed fitting and the other is with a condulet (LB) with double locknut. Say that both of these were feeds to our classified area, I would say that the LFMC with listed fitting would be ok, but based on 502.30(A), I would say that the double locknut would not be acceptable. While double locknuts are acceptable for bonding over 250V in unclassified areas (250.97(2)), I'd be led to believe that this would not be acceptable for bonding of raceways for circuits entering a classified area. Or am I reading too much into this?

Thanks again for your replies.