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borderbuster 07-07-2007 11:03 PM

grounding pole building sheet metal?
Should the sheet metal (steel) siding and roofing of a post frame building be grounded?
If so should it be bonded to the ground bar or ground rod of the building's electrical panel?

My pole building sheet metal does not contact the earth. The metal is painted and may have electrical bonding between the panels either at a common fastener or bare spots in the finish.(or maybe not, who knows)

Also the electrical panel is installed on wood framing with no fasteners touching the metal siding. The electrical panel ground bar is bonded to ground rods but the bond is insulated from the metal siding.

I have looked at similar buildings(wood frame) in my area and see no evidence of grounding of the sheet metal except by accidental contact.

This building is used as a machine shop/storage building, no farm animals.

Is there a right way? or a better way? or does it make any difference?

Thanks, Borderbuster

Stubbie 07-08-2007 12:20 AM

Structural metal. If exposed structural metal that forms a metal building frame is likely to become energized, you must bond it to (Fig. 3) one of these [250.104(C)]:
  • Service equipment enclosure
  • Grounded neutral service conductor
  • Grounding electrode conductor, if sized per Table 250.66
  • One or more of the electrodes of the grounding electrode system
This rule doesn't require you to bond sheet metal framing members (studs) or the metal skin of a wood frame building , but doing so is a good practice. Size the bonding jumper for the structural metal per Table 250.66, based on the feeder or service conductors that supply the building (or structure). This bonding jumper must be:
  • Copper where within 18 inches of earth [250.64(A)].
  • Securely fastened and adequately protected, if exposed to physical damage [250.64(B)].
  • Installed without a splice or joint, unless spliced by irreversible compression connectors listed for the purpose or by the exothermic welding process [250.64(C)].

The text and image borrowed from Mike Holt enterprises

Pictures speak a thousand words

Hope this helps

borderbuster 07-08-2007 02:11 AM

Thanks Stubbie,

I did read Mike Holt's interpretation, although my internet search didn't find the one you posted here.
Since grounding the sheet metal is not mandatory, but preferred, it sounds like expense may be the big issue. I will give it some consideration anyway.


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