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#96009 - 10/30/05 03:17 PM metal roofs  
watersparkfalls  Offline
Joined: Mar 2005
Posts: 216
Washington...Not DC
where does everybody stand on bonding metal roofs? the code i beleive but cant quote says any metal that may become energized shall be bonded, i always bond steel and tin but am working on a house which will have a metal roof and am wondering if i need to bond the roof?

thoughts comments always appreciated.

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#96010 - 10/30/05 05:40 PM Re: metal roofs  
jw electric  Offline
Joined: Sep 2005
Posts: 106
Asheboro, NC
Read the first sentence and see it you think it fits.

250.104 (C) Structural Metal. Exposed structural metal that is interconnected to form a metal building frame and is not intentionally grounded and is likely to become energized shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or the one or more grounding electrodes used. The bonding jumper(s) shall be sized in accordance with Table 250.66 and installed in accordance with 250.64(A), (B), and (E). The points of attachment of the bonding jumper(s) shall be accessible.


#96011 - 10/30/05 08:07 PM Re: metal roofs  
renosteinke  Offline
Cat Servant
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
I must disagree. As I understand the term, "structural metal" is something like an I-Beam; simple sheet metal roofing would not qualify.

More to the a conventional steel building- I beam frame, sheet metal siding and roof- with all those screws and bolts, it would be darn near impossible to avoid bonding a piece of metal.

#96012 - 10/30/05 08:17 PM Re: metal roofs  
George Little  Offline
Joined: Jan 2004
Posts: 1,489
Michigan USA
I agree with Reno. But tell me- was I mistaken or were we using the '02 code for our discussion here unless specified other editions? This thread is directing us to the '05 code???

George Little

#96013 - 10/30/05 08:42 PM Re: metal roofs  
harold endean  Offline
Joined: Feb 2002
Posts: 2,233
Boonton, NJ
Just for kicks, lets throw this one in here. If the whole house is made of wood, but there is 1 steel I-beam running down the center of the house. Would you bond that I-beam to the electrical wiring?

#96014 - 10/30/05 09:07 PM Re: metal roofs  
Electricmanscott  Offline
Joined: Jan 2002
Posts: 1,457
Holden, MA USA
Harold to answer your question, no I would not bond it and no it would not be required to be bonded nor would a metal roof.

#96015 - 10/31/05 12:52 AM Re: metal roofs  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,059
I always looked at the intent that metal that may become energized could be bonded to the EGC of the circuit likely to energize it.
The caddy clamp that holds the box to the beam was usually enough to make me happy. The tricky one is aluminum siding where you have isolated sections with a box on it like a gable end on a CBS house with a flood light.

Greg Fretwell

#96016 - 10/31/05 09:05 PM Re: metal roofs  
HLCbuild  Offline
Joined: Dec 2004
Posts: 209
Herndon,Va USA
The metal roof is a "roof covering", not part of a structural metal bonding required

#96017 - 10/31/05 09:57 PM Re: metal roofs  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,059
The commentary after 250.116 sums up my opinion.
Because metal siding on buildings is not electrical equipment, it is outside the scope of the Code [see 90.2(A)]. Therefore, the Code cannot require that it be grounded. Quite often, however, luminaires, signs, or receptacles are installed on buildings with metal siding that could become energized. Grounding of metal siding reduces the risk of shock to persons who may come in contact with the siding.

My take was always that if the attached equipment was electricaly connected to the metal material it was bonded. In the case of a roof I would feel the same way. If equipment is installed up there, bond the roof to the EGC of the equipment. It would usually be hard not to if the equipment is metal.

Greg Fretwell

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