bonding of structural steel in 1 and 2 family homes

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henelectric

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i am an electrical inspector in the state of new jersey. i have asked contractors to bond all structual steel used in construction in many of the larger homes being built today. as a reference to this i have been quoting NEC article 250.4(a)4. i have run into some disagreement on this and would like to know how the folks at mike holt, as well as other readers, feel about this. thank you
 
Re: bonding of structural steel in 1 and 2 family homes

We recently discussed this issue at a state IAEI meeting after one jurisdiction reported a woman whom received a severe shock in her bathroom while touching her medicine cabinet.

It was determined that the installer used a 3" screw which penetrated NM cable strapped to the back side of the same metal stud.

In many cases, installers will run NM cable along the "channel" side of a metal stud or tie wrap the NM directly to the metal stud. Though the 1? rule is generally complied with, the flexibility of the cable tends to force it closer to the stud face.

We have considered requesting contractors to use stand-offs or other securing/supporting means that separates the cables from the metal studing or bond the metal studing. It seems to be something we are heading towards here in Florida as well.
 
Re: bonding of structural steel in 1 and 2 family homes

What would energize that steel? I would fight you on this, because it is not likely that the steel would become energized. Yes, it is possible, but not likely and therefore bonding is not required.
Don
 
Re: bonding of structural steel in 1 and 2 family homes

You may be on shaky ground here. The key phrase here and in 250.104(C) is "likely to become energized" Might be hard to prove this.
 
Re: bonding of structural steel in 1 and 2 family homes

I'm with Don and John. Selling the "likely to become energized" part of 250.4(A)(4) is a hard sell. I'm not convinced that simply because someone uses a metal framing member that it is likely to become energized.

Now it the metal framing member qualified as the "Metal Frame of the Building or Structure" than I would agree that it is an available electrode and must be bonded according to 250.50, which directs you to 250.52(2).

[ January 21, 2006, 01:50 PM: Message edited by: infinity ]
 
Re: bonding of structural steel in 1 and 2 family homes

In my mind if it is "likely to become energized" somebody f'd up. This would mean that at some point it will become energized. With a properly installed wiring system a piece of steel in a residence is not likely to become energized.

I see you having no legal justification to require this.
 
Re: bonding of structural steel in 1 and 2 family homes

250.50 defines the Grounding Electrode System. Structural steel is part of it, and yes must be connected to earth potential. (What ESD people call common point grounding; the System includes any and all conductive surfaces, to me. Even separate concrete slabs.) The one exception, the formal intrpretation, seems to imply that it is not required to break open concrete for access if it's already poured.
250.50 G. E. System:
"If available on the premises at each building or structure served, each item in 250.52(a)(1) through (a)(6) shall be bonded together...."
Now that I wrote it down, I see the work "shall" in there. As in, required in NFPA 70.

[ January 21, 2006, 07:50 PM: Message edited by: peteo ]
 
Re: bonding of structural steel in 1 and 2 family homes

peteo,
It is unlikely that a dwelling unit has a metal frame that would be required to be used as a grounding electrode.
Don
 
Re: bonding of structural steel in 1 and 2 family homes

Could someone give an example of what could be "likely to become energized" in an otherwise code compliant installation?

Thank You.
 
Re: bonding of structural steel in 1 and 2 family homes

I agree, my wiring never produced situations where devices were likely to be energized. Likely implies most probable. Possible, yes; likely, no.
 
Re: bonding of structural steel in 1 and 2 family homes

Originally posted by apauling:
I agree, my wiring never produced situations where devices were likely to be energized. Likely implies most probable. Possible, yes; likely, no.
Click to expand...
WOW we agree again. :D

I think you summed it up very nicely.

Anything is possible however 'likely' IMO indicates 'to be expected'.
 
Re: bonding of structural steel in 1 and 2 family homes

Considering the word "likely" is a vague and unenforceable per the NEC style manual, I simply drop it when reading a section. So when reading a section like 250.4(A)(4), I see like this, "Electrically conductive materials that are to become energized shall..."

This makes it a "will or will not" consideration. That being said, what my jurisdiction or state determines to enforce is out of my control in some cases.
 
Re: bonding of structural steel in 1 and 2 family homes

I do not agree that Likely is a vauge term, check out any dictionary. Every dictionary I looked at used a form of the word "Likely" everytime it tried to define "possible" and "probable"

According to Webster's for Kids: adjective "very possibly going to happen", adverb "without great doubt : PROBABLY".

So, is it really okay just to ignore any descriptive words (adverbs and adjectives) we don't like in the NEC?

edit: grammar

[ January 22, 2006, 01:46 PM: Message edited by: jim dungar ]
 
Re: bonding of structural steel in 1 and 2 family homes

Bryan,
I might agree with you, had CMP 5 not made a change in the wording used in this code section. In the 2002 code, the words "may become energized" were used. In that case, you would always have to bond the steel, because it is possible, no matter how unlikely, for any conductive object to become energized. In the 2005 code the word "may" was replaced by the words "likely to". Now the rule has changed and if the conductive object is "not likely to become energized" then bonding is not required. In a correctly installed electrical system it is not likely that conductive items will become energized. Yes, it is possible, but it is not likely.
Don
 
Re: bonding of structural steel in 1 and 2 family homes

Originally posted by bphgravity:
We recently discussed this issue at a state IAEI meeting after one jurisdiction reported a woman whom received a severe shock in her bathroom while touching her medicine cabinet.

It was determined that the installer used a 3" screw which penetrated NM cable strapped to the back side of the same metal stud.
Click to expand...
Sounds as though the medicine cabinet installer screwed up. If the 1.25" was overcome with a 3" screw, how is the electrician to blame?

When installing cable in the "C" channel of a steel stud where the MC goes, these keep the cable the required 1.25" away from screws. Also good for the switches next to doors. :)
cs6_c15.GIF
 
Re: bonding of structural steel in 1 and 2 family homes

When installing cable in the "C" channel of a steel stud where the MC goes, these keep the cable the required 1.25" away from screws.
Click to expand...
Is this required when running MC through metal studs?
 
Re: bonding of structural steel in 1 and 2 family homes

Originally posted by infinity:
When installing cable in the "C" channel of a steel stud where the MC goes, these keep the cable the required 1.25" away from screws.
Click to expand...
Is this required when running MC through metal studs?
Click to expand...
MC = Medicine Cabinet in this case. :D
 
Re: bonding of structural steel in 1 and 2 family homes

I meant medicine cabinet. But yes, I believe it's required for MC cable too.

300.4. Can't get more specific than that, I can't open the NEC right this second. (Big Tomb-Raider Cheat webpage open right now for the wife.) :D
 
Re: bonding of structural steel in 1 and 2 family homes

I don't think it's required George, but when you can, provide a code reference. Not now, don't want you to upset the Mrs. :)
 
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