Yesterday I inspected a house with metal trusses. The client was asking if the romex in the attic should be run in conduit. I told him that I could not remember any code problem on that except when it runs through the metal trusses, but he was concerned about it running across the trusses. I could not find any where that was addressed in the NEC. Anyone that can help me on this?
As long as it’s properly secured, and protected (as required) from physical damage, there’s no problem with NM and metal/steel framing. . .
The question come up after he was talking about using the attic for storage. He was concerned about the storage possibly being on top of the wiring and nicking it and it being in contact with the trusses.
This problem an happen be it metal or wood…the same physical damage condition would exist regardless…
The wires should be six feet from the scuttle entrance and properly secured. Here is what the NEC says about bonding of structural steel, hope it helps.
- 250.104 Bonding of Piping Systems and Exposed Structural Steel.
- © Structural Steel. Exposed structural steel that is interconnected to form a steel building frame and is not intentionally grounded and may 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 found this video, Sad story.
Currently the NEC does not consider metal studs in a residential framing to be “Structual Steel” so this would not apply.
However most of the time if metal studs are used then metal boxes are also used and in this case if the box is bonding properly the joined framing members would as well as part of the installation and application.
Rumors are that this may change in the 2008 revision…right now metal studs in a house are not considered to meet the " Structual Steel " requirement.
FYI- if indeed it was determined by the AHJ that the wiring would be likely to become energized ( which is a hard and if not impossible task ) he could wish for sections to be bonded…but this again would take place simply by using metal device boxes and properly run EGC’s within the dwelling.
Thanks for the info. I did not know they didnt consider residential steel framing structual steel.
Did you watch the video link and do you think AFIs or GFIs would have prevented the the accident?
If the perspective owners are considering using the attic for storage, they’d be well advised to see if it is structurally suitable for such use. Most attics without floors are not so rated.
Now because of issues with bonding in that it is very hard in those types of installations to ensure it is all bonding properly…metal boxes with proper connections may have assisted and it is no doubt that they are looking at this for the 2008 because of this case…but a dual AFCI/GFCI breaker in my mind would have given him a better chance…
Know it looks like the sheetrock screw drove in the 12 AWG wire…and amazing enough I guess it only contacted the HOT and did not come in contact with the equipment grounding conductor…
Very sad story and you have to feel for the family…
I wanted to add…I am guessing he got ahold of that metal duct as it makes contact with the metal studs and then rested a hand over on a properly bonded washer machine to obtain the ground…and well…sad event.
Florida has added bonding metal studs to the building code. A properly bonded metal box in each isolated segment of the wall will suffice.
Btw one solution for the wiring in the attic is to see if the manufacturer allows punching the web of the steel. Then you could pop in a grommet and pull the wire in below the face.