501.30(A)

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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Suppose one has an enclosure in an unclassified area feeding equipment in a classified area.

A few questions about this provision.

Does this provision require bonding of both ends of a conduit that starts in an unclassified area?

Does the bonding means have to be a wire?

can you run a single wire in one conduit from an unclassified area and use it to bond multiple conduits where they terminate in a classified area?
 

Gregg Harris

Senior Member
Location
Virginia
Suppose one has an enclosure in an unclassified area feeding equipment in a classified area.

A few questions about this provision.

Does this provision require bonding of both ends of a conduit that starts in an unclassified area?

Does the bonding means have to be a wire?

can you run a single wire in one conduit from an unclassified area and use it to bond multiple conduits where they terminate in a classified area?

Se if this helps

250.100 Bonding in Hazardous (Classified) Locations. Regardless of the voltage of the electrical system, the electrical continuity of non?current-carrying metal parts of equipment, raceways, and other enclosures in any hazardous (classified) location as defined in 500.5 shall be ensured by any of the bonding methods specified in 250.92(B)(2) through (B)(4). One or more of these bonding methods shall be used whether or not equipment grounding conductors of the wire type are installed.

250.92(B)
(2)
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Connections utilizing threaded couplings or threaded hubs on enclosures if made up wrenchtight

Changed From 2008

?
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250.92(B)(2): Revised terminology to improve understanding of acceptable means of bonding connection.


(3)
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Threadless couplings and connectors if made up tight for metal raceways and metal-clad cables

(4)
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Other listed devices, such as bonding-type locknuts, bushings, or bushings with bonding jumpers
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
This is a great application for Section 90.1(C). Section 501.30 and its predecessor 501.16 (2002 NEC and before) have been rewritten so many times, I genuinely believe very few recognize that it simply means:

"The locknut-bushing and double-locknut types of contacts shall not be depended on for bonding purposes..."

AND IF

a locknut-bushing OR double-locknut is used

THEN "...bonding jumpers with proper fittings or other approved means of bonding shall be used."


The rest of the Section is pretty much unnecessary, if the wiring methods are otherwise consistent with the requirements of Section 501.10 and Article 250.

Of course, it doesn't help that this is one of the few Sections in Article 501 where Division 1 and 2 methods are dumped into a common statement since locknut-bushing and double-locknut types of contacts couldn't be used in Division 1 in the first place.

I can't remember how many times the Section has been "clarified", but IMO the unintended consequences of each "clarification" just further muddies the issue.
 
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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
This is a great application for Section 90.1(C). Section 501.30 and its predecessor 501.16 (2002 NEC and before) have been rewritten so many times, I genuinely believe very few recognize that it simply means:

"The locknut-bushing and double-locknut types of contacts shall not be depended on for bonding purposes..."

AND IF

a locknut-bushing OR double-locknut is used

THEN "...bonding jumpers with proper fittings or other approved means of bonding shall be used."


The rest of the Section is pretty much unnecessary, if the wiring methods are otherwise consistent with the requirements of Section 501.10 and Article 250.

Of course, it doesn't help that this is one of the few Sections in Article 501 where Division 1 and 2 methods are dumped into a common statement since locknut-bushing and double-locknut types of contacts couldn't be used in Division 1 in the first place.

I can't remember how many times the Section has been "clarified", but IMO the unintended consequences of each "clarification" just further muddies the issue.

It does seem rather convoluted if that is all it means.

I thought the sum total meant you had to run a wire type EGC, and some how you had to have a wire type EGC that went all the way back to the GES.

But back to what i originally asked, which came up when I visited a site last week where a control panel sits outside of a classified area but all the wiring goes underground into the classified area. It did not appear to me that they had taken any special pains to bond any of the conduits, at least on the unclassified side.


Does this provision require bonding of both ends of a conduit that starts in an unclassified area?
A: No. However, if you want to use the conduit as the bonding means you could not use a locknut or double locknut method at the unclassified end.

Does the bonding means have to be a wire?
A: I believe Bob A's explanation. It actually makes sense the way he put it.

can you run a single wire in one conduit from an unclassified area and use it to bond multiple conduits where they terminate in a classified area?
A: less obvious. but I think the answer would be yes, as long as all the conduits end up being bonded in a code legal way and the bond extends back to the GES.
 
Location
Calexico
Bond, Bond, Bond

Bond, Bond, Bond

Does this provision require bonding of both ends of a conduit that starts in an unclassified area?

Yes.

In the 2011...look at 501.30(A) It says back to the service with the exception saying back to the nearest point where your grounded conductor and electrode are connected.

Intent being, they want to ensure the connection back to the supply. If something happens, that over-current device needs to clear the fault immediately, even if it is 20 years down the road.

Does the bonding means have to be a wire?

No.

Article 250.100 jumps you to 250.92 (B) (2)-(4) This lays out what you can use. Threaded conduit or threadless couplings. You can also use ground bushings...that sounds to me like the easiest way, specially if your in an unclassified area.

Can you run a single wire in one conduit from an unclassified area and use it to bond multiple conduits where they terminate in a classified area?

Yes.

This a typical wiring method. As long as they are sized accordingly.
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
Responding directly to Question 1. If the raceway is used as the EGC, and installed consistently with Section 501.10 and Article 250 as I mentioned before, it will be bonded at both ends; either to the service or SDS as the case may be.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Does this provision require bonding of both ends of a conduit that starts in an unclassified area?

Yes.

Are you sure you can't run a green wire with the conduit and and use that to bond it at the classified end?

There is no requirement to take any special pains on the unclassified end.

In fact, I think one could properly bond one conduit in the unclassified area, run them all out to the classified area with no green wire at all, and bond the other ends of the conduits together and be compliant.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Responding directly to Question 1. If the raceway is used as the EGC, and installed consistently with Section 501.10 and Article 250 as I mentioned before, it will be bonded at both ends; either to the service or SDS as the case may be.


I would not argue with that.

Something else I noticed there. For some reason they ran a bare wire for the GEC UG. Is that normal? I thought there was some kind of rule about not running uninsulated wire UG.

In any case, what is the benefit of running a bare wire over an insulated one? it seems like it would be a lot easier to find insulated wire.
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
I would not argue with that.

Something else I noticed there. For some reason they ran a bare wire for the GEC UG. Is that normal? I thought there was some kind of rule about not running uninsulated wire UG.

In any case, what is the benefit of running a bare wire over an insulated one? it seems like it would be a lot easier to find insulated wire.
In refineries it's quite common to have an entire bare copper network underground as part of the lightning protection system. It must then be bonded to the grounding electrode system. [See Section 250.106]
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
In refineries it's quite common to have an entire bare copper network underground as part of the lightning protection system. It must then be bonded to the grounding electrode system. [See Section 250.106]

I have seen that before. But never saw anyone do it with a #8 GEC.
 
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