panel board as an EGC

[nickelec]

How many panels, cabinets have provisions for multiple egc bars? I have seen some with 2 different possible mounting locations, if you install an EGC bar say with self tappers anywhere wouldn't that voilate the ul listing of that can by not using it the way it was intended?

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It wasn't intended*

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[necGuru]

Self tappers violate the listing as the equipment was not tested that way. Self tapping screws, sheet metal screws, drywall screws = no, No, NO!

 

[nickelec]

Self tappers violate the listing as the equipment was not tested that way. Self tapping screws, sheet metal screws, drywall screws = no, No, NO!

That's my point lol


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[don_resqcapt19]

This is a problem with the code itself. We all use boxes and enclosures as EGCs, but there is nothing in the NEC that says a metallic box or enclosure is an EGC. I have been thinking about a PI on this issue.

 

[don_resqcapt19]

250.96 (A) specifically mentions enclosures, which allows the practice .


I think this is merely a case of that inspector once read that the building steel is not to be used as a bonding path. A panel board is not '' building steel'', but of course many inspectors once countered with that will begin with the '' we interpret this to mean the panel boards are what this is referring to.....

Nothing in 250.96 specifically says that the enclosure can be used as an EGC...it just says where it is used as such it must be bonded. Everyone, including CMP 5 just assumes that the enclosure can be used as an EGC, but the code never actually tells us that.

 

[wwhitney]

there is nothing in the NEC that says a metallic box or enclosure is an EGC. I have been thinking about a PI on this issue.

I submitted a PI to add one item to the list in 250.118 "(15) Metallic equipment enclosures." My substantiation is below. Feel free to submit your own PI or to propose a better substantiation, I'm happy to change my PI.

Cheers, Wayne

There is currently a conflict between 250.118, the definition of Equipment Grounding Conductor, and common practice.

When using an equipment grounding conductor not of the wire type, such as rigid metal conduit, common practice is to rely on metallic equipment enclosures, such as a panelboard cabinet, to provide continuity for the "ground-fault current path" between sections of conduit. As such, per the Article 100 definition, metallic equipment enclosures are Equipment Grounding Conductors. And they certainly "enclose circuit conductors", so they fall under the scope of 250.118. However, the list in 250.118 does not presently include metallic equipment enclosures.

The simplest way to resolve this logical conflict would be to add an additional item to the list, "(15) Metallic equipment enclosures." If the Technical Committee prefers, the scope of 250.118 could instead be limited to equipment grounding conductors run with or enclosing circuit conductors "between equipment enclosures."

 

[FionaZuppa]

I submitted a PI to add one item to the list in 250.118 "(15) Metallic equipment enclosures." My substantiation is below. Feel free to submit your own PI or to propose a better substantiation, I'm happy to change my PI.

Cheers, Wayne

There is currently a conflict between 250.118, the definition of Equipment Grounding Conductor, and common practice.

When using an equipment grounding conductor not of the wire type, such as rigid metal conduit, common practice is to rely on metallic equipment enclosures, such as a panelboard cabinet, to provide continuity for the "ground-fault current path" between sections of conduit. As such, per the Article 100 definition, metallic equipment enclosures are Equipment Grounding Conductors. And they certainly "enclose circuit conductors", so they fall under the scope of 250.118. However, the list in 250.118 does not presently include metallic equipment enclosures.

The simplest way to resolve this logical conflict would be to add an additional item to the list, "(15) Metallic equipment enclosures." If the Technical Committee prefers, the scope of 250.118 could instead be limited to equipment grounding conductors run with or enclosing circuit conductors "between equipment enclosures."

with no egc wire would you use bonding washers at the cabinet?
although rare, a well coated box may not make good low ohms contact to the conduit. to me, the box is really there as a protective enclosure, which will be bonded to earth. with various box coatings (primer/paint, powder, etc) perhaps its why enclosure do not get listed in UL as egc?

does the verbiage in 250 say that the enclosure itself is not an egc, but rather the use of bonding to complete the egc ckt is to be used?

 

[Dennis Alwon]

The code specifically states that the metal of an enclosure cannot be used to connect the neutrals however there is no statement as such for the equipment grounding conductor. I say it is fine.

If you want use a bonding jumper the size of the largest equipment grounding conductor.

 

[macmikeman]

Nothing in 250.96 specifically says that the enclosure can be used as an EGC...it just says where it is used as such it must be bonded. Everyone, including CMP 5 just assumes that the enclosure can be used as an EGC, but the code never actually tells us that.

I disagree heartedly with this post of yours , so that's like a first for me. (A) General. Metal raceways, cable trays, cable armor , cable sheath, ENCLOSURES, that are to serve as equipment grounding conductors...............

The 8 words following enclosures, due overly seem to give permission specifically.
And also when the code doesn't specifically prohibit a practice, then it is implied that the practice is allowed.

 

[macmikeman]

For what it is worth, I always carry around a 10-32 tap that can be chucked into my cordless drills. First I bust a hole thru sheet metal using a self tapping tek screw, withdraw that and use the starter hole for my tapping bit. It's all over so fast the patient hardly notices a thing....... Then I screw in a (now this will cause an uproar) green 10-32 screw that they sell by the bag of 50 at the Home Depot near where the wirenuts are displayed. Those are to short for grounding busbars, but I also have a supply of longer ones that work fabulous to clamp grounding busbars with my van at all times. Everybody should learn to carry those 10-32 tapping bits around in their toolbags along with a few tek screws for starter holes all the time with them. They will be used and come in quite handy.

 

[wwhitney]

(A) General. Metal raceways, cable trays, cable armor , cable sheath, ENCLOSURES, that are to serve as equipment grounding conductors...............

The 8 words following enclosures, due overly seem to give permission specifically.

The issue I have is that 250.118 as written prohibits metal enclosures from being used as an EGC, since they do "enclose the circuit conductors", but are not listed in 250.118. Nothing in 250.96 gives any relief from this 250.118 prohibition. I'm sure the prohibition isn't intentional, so the wording in 250.118 needs to be changed.

Cheers, Wayne

 

[petersonra]

I disagree heartedly with this post of yours , so that's like a first for me. (A) General. Metal raceways, cable trays, cable armor , cable sheath, ENCLOSURES, that are to serve as equipment grounding conductors...............

The 8 words following enclosures, due overly seem to give permission specifically.
And also when the code doesn't specifically prohibit a practice, then it is implied that the practice is allowed.

250.96 tells you that a metallic enclosure used as an EGC has to be bonded, but does not actually tell you that it can be used as an EGC.

Since 250.96 also refers to "other metal non–current-carrying parts that are to serve as equipment grounding conductors". Does that give permission to use any chunk of non-current carrying metal as an EGC?

250.118 Types of Equipment Grounding Conductors.
The equipment grounding conductor run with or enclosing
the circuit conductors shall be one or more or a combination
of the following:

90.5 Mandatory Rules, Permissive Rules, and Explanatory
Material.
(A) Mandatory Rules. Mandatory rules of this Code are
those that identify actions that are specifically required or
prohibited and are characterized by the use of the terms
shall or shall not.

It seems quite clear that the use of the word "shall" in 250.118 makes the requirement mandatory and not a suggestion.

 

[kwired]

How many panels, cabinets have provisions for multiple egc bars? I have seen some with 2 different possible mounting locations, if you install an EGC bar say with self tappers anywhere wouldn't that voilate the ul listing of that can by not using it the way it was intended?

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IMO if you use the bar intended for the cabinet, and the mounting hardware and pre-made holes intended for mounting that bar (some have multiple places within the cabinet where it can be placed), you do not need to remove any paint or worry about if enough mounting screw threads are engaged to make sufficient contact.

OTOH if you use another manufacturers bar or mount it in your own selected position then you need to remove paint (if a painted enclosure, and possibly can have issues with not enough threads being engaged in the wall of the enclosure. Needs to be two threads engaged, so if you have 8-32 or 10-32 screws it must be 1/16 inch thick to get two threads, other option is long enough screws to put a nut on back side, but that can be difficult if back side is against a mounting surface.

 

[don_resqcapt19]

The code specifically states that the metal of an enclosure cannot be used to connect the neutrals however there is no statement as such for the equipment grounding conductor. I say it is fine.

If you want use a bonding jumper the size of the largest equipment grounding conductor.

There is nothing that says that metallic enclosures are EGCs. We have a rule in 314.28(C) that requires a metallic cover to comply with the grounding requirements of 250.110. 250.110 specifically requires that the box cover be connected to an Equipment Grounding Conductor. Without a change to 250.118 telling us that the box is an ECG, you have to connect a bonding jumper to the box cover. Yes, we never install a bonding jumper and we use metallic enclosures as EGCs all the time, but there is nothing in the code that actually permits us to do that.

 

[kwired]

There is nothing that says that metallic enclosures are EGCs. We have a rule in 314.28(C) that requires a metallic cover to comply with the grounding requirements of 250.110. 250.110 specifically requires that the box cover be connected to an Equipment Grounding Conductor. Without a change to 250.118 telling us that the box is an ECG, you have to connect a bonding jumper to the box cover. Yes, we never install a bonding jumper and we use metallic enclosures as EGCs all the time, but there is nothing in the code that actually permits us to do that.

How many junction box covers and conduit body covers have you connected a bonding jumper to? I'm not sure if I ever have on a conduit body, junction box, maybe. Never with a cover on a panelboard cabinet, but occasionally on other hinged cover enclosures, especially if there are devices mounted to the cover (pushbuttons, selector switches, etc.)

:blink:

 

[don_resqcapt19]

How many junction box covers and conduit body covers have you connected a bonding jumper to? I'm not sure if I ever have on a conduit body, junction box, maybe. Never with a cover on a panelboard cabinet, but occasionally on other hinged cover enclosures, especially if there are devices mounted to the cover (pushbuttons, selector switches, etc.)

:blink:

I have very rarely done that, but I think that the current code wording very clearly requires that.

 

[kwired]

I have very rarely done that, but I think that the current code wording very clearly requires that.

Which one, or all of them?

 

[don_resqcapt19]

Which one, or all of them?

All of them.