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While grounding power sockets in modular prefabricated steel buildings (see Light Gauge Steel Frame Technology), can we just connect the ground wire to the steel frame of the building itself? as the entire frame is grounded. Would that eliminate the need of other systems required for grounding?

No one can actually “touch” the steel frame, if you’ve concerns about the entire structure being on live power. There are layers of insulation: rock wool between the panels of the steel frame, then OSB boards or thermopine, then entire structure is covered with water proof membrane, then cladded with steel, and on the inside there’s thermopine and wood/paint on cement sheet.

Can someone tell me how can I get to know if such practices are allowed in the US? Which local authority to contact?

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    $\begingroup$ Check the NEC for the detail. $\endgroup$ – Solar Mike Jan 26 at 10:07
  • $\begingroup$ @SolarMike NEC? Can you please elaborate $\endgroup$ – TheReal_Skywalker Jan 26 at 11:36
  • $\begingroup$ National Electric Code ... but you should know that, any research would have given that. $\endgroup$ – Solar Mike Jan 26 at 11:52
  • $\begingroup$ @SolarMike I’m not from the US. I wrote “US” in the post because I wanted to know the standard followed there. $\endgroup$ – TheReal_Skywalker Jan 26 at 12:36
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In the US, electrical installations are primarily governed by the National Electrical Code, also known as NEC or NFPA 70 (It's official designation.) You can read the code for free (with an account) on NFPA's website. Section 250.104(C) of the 2017 code defines the requirements for bonding of "Structural Metal." It requires bonding of exposed structural metal that is likely to become energized. One can argue the definitions of exposed and likely with the inspector, but if there is insulation-on-stud contact, abrasion is possible, and if there are screws penetrating the layers of "insulation" you reference, then it's possible for a person to make electrical contact with the wall framing. Do note that even without screws penetrating, rock wool, OSB, and waterproofing membranes are not usually tested and rated for an insulating value. While they have some insulation value, if you can't prove that the breakdown voltage is per code, they will not be considered as insulators. True insulators are usually rated and listed by an NRTL such as UL.

For residential applications, the International Residential Code also applies, and it has some specific electrical requirements (see section E3609) but they are not specific on this matter. If your prefab buildings aren't one or two family residences, then this code won't apply anyway.

In all cases, the safest thing is to discuss it with the electrical plan checker at the department of building ad safety for the municipality or county that the project will be installed in. As long as the plans clearly show what will and won't be bonded, and the plan checker agrees that you're complying with the code, you can usually explain the logic to an inspector.

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