metal roofs - ECN Electrical Forums

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.
thanks,
h20

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.

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 point....in 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.

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???

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?

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.

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.

The metal roof is a "roof covering", not part of a structural metal frame...no bonding required

The commentary after 250.116 sums up my opinion.

Quote

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.