Feeder support when entering subpanel

Status
Not open for further replies.
Joe.B

Joe.B

Senior Member
Location
Myrtletown Ca
Occupation
Building Inspector
In general most electricians I've inspected for will add some 2X blocking within 12 in of where the feeder enters the subpanel, occasionally when it's not installed and I point it out it doesn't seem to be a problem, like they just forgot and they're happy to install it. I'm inspecting a new apartment building and each unit has a subpanel with a 4-wire feeder coming vertically through the stud bay and into the 100 amp subpanel (all electric units) through the top or bottom with more than 4 1/2 feet between top or bottom plate and the panel. I called it out as a correction and I used 334.30 Securing and Supporting. The electrician wasn't there when I did the rough inspection and when the GC gave him the correction the electrician just used framing nails bent over to "secure" the feeder to the inside of the stud bay. I said that I was pretty sure it needed to be an "approved" staple, cable tie, strap or similar and that usually I see it installed with blocking between the studs. He got huffy and decided that I was way off, and he may be right. I have no problem being corrected. I said I'd take some time to read the code and we would meet tomorrow. One thing he said is that 334.30 doesn't apply to feeders even though (in my mind) it's NM sheathed cable because it's a "feeder", ok I can understand that I could be wrong there but where should I be looking? It's not a service entrance cable, right? Any advice would be appreciated.
 
As noted in Post 3, the Art 338 rules require Art 334 support which states:

334.30 Securing and Supporting. Nonmetallic-sheathed cable shall be supported and secured by staples; cable ties listed and identified for securement and support; or straps, hangers, or similar fittings designed and installed so as not to damage the cable,
That would seem to preclude bent nails.
 
Thanks a bunch! I appreciate the redirect to 338, that's probably what he was getting at when I was siting 334, and I love that 338 calls out 334 for interior installations though! Yeah the nail is a no go, but neither does it seem that 2X blocking is required. Maybe more of a best practice thing? Do any of you block between the studs to provide a solid anchor point, or is it pretty common to turn it over and support it by the nearest stud?

It's SE ( type R) Cable, 2/0 4-wire. I think they upsized from 1/0 because a couple of the apartments have long runs. In my mind SE cable is a type of non-metallic cable so I was just a couple sections off.

Again, thank you all for the support.
 
I think you might be served in this by the requirements of 312.5(C)(1) Each cable is fastened within 300mm (12 in.), measured along the sheath , of the outer end of the raceway.
Also for the SE cable criteria found in 230.51(A) "12 in.".
338.10(B)(4) SE and USE Cables, references 334 compliance and 334.30 also says "within 12 in." of entry into box.
How you get that is preference, one method is as shown with a 2X fastened, or if backer is large enough to get a fastening point within the 12 inch requirement is another way.
Even MC and conduit has a 12 inch requirement.
OP is in the right to call it out. And the electrician (if it was him and not the GC) was throwing a tantrum by bending a nail over to make the fastening point. I would lean to believing the GC doing it. Every requirement I've seen is if for connect or securing means be of a listed type.
@LarryFine, nice installation picture. But how many times you smash your fingers doing those staples?
To the OP, do you of have you done other inspections for this Electrician?
 
LarryFine said:
Never. I hold staples with the tip of my pliers.
Click to expand...
Was wondering, I do that too, too many hits to my fingers. But I've seen guys that never use pliers and seem to not have issue with hitting finger. Got the DeWalt cable stapler now, makes it a lot faster, and no smashed fingers, great in those odd spaces a hammer swing not easy.
 
I usually block it out. But a lot of guys will use a 16 penny nail and not bend it but tie wrap it to the nail. This way it's not up against the stud and stays clear of a missed stud nail by sheetrockers.

But then an inspector can say well what type of nail is it. Maybe it is one that has been treated with chemicals that will eat through the insulation of the wire. :rolleyes:
 
Fred B said:
I think you might be served in this by the requirements of 312.5(C)(1) Each cable is fastened within 300mm (12 in.), measured along the sheath , of the outer end of the raceway.
Also for the SE cable criteria found in 230.51(A) "12 in.".
338.10(B)(4) SE and USE Cables, references 334 compliance and 334.30 also says "within 12 in." of entry into box.
How you get that is preference, one method is as shown with a 2X fastened, or if backer is large enough to get a fastening point within the 12 inch requirement is another way.
Even MC and conduit has a 12 inch requirement.
OP is in the right to call it out. And the electrician (if it was him and not the GC) was throwing a tantrum by bending a nail over to make the fastening point. I would lean to believing the GC doing it. Every requirement I've seen is if for connect or securing means be of a listed type.
@LarryFine, nice installation picture. But how many times you smash your fingers doing those staples?
To the OP, do you of have you done other inspections for this Electrician?
Click to expand...
Yes they do a lot of work here, but the owner is getting older and I don't see him on the job much anymore. His son who I've seen a lot of has started winning a lot of his car races, suddenly he's not on the job much. The gentleman running this job is an experienced electrician locally but new to this company, I've never inspected his work. He knows his stuff on some things, but seems to be butting heads with the GC. When I showed him the 12" rule he said he can't staple/strap it to the stud within 12" because the wire won't bend like that. Go figure. So he tells the GC that he needs them to block everything out, GC looked at him like he was crazy and said it's part of the electrical work. That's when I walked away. Thanks again for the help!
 
wwhitney said:
So some plastic plumber's tape (that perforated strap) secured across the stud bay would comply with 334.30?
Click to expand...
I guess my suggestion wasn't clear: I mean use a length of perforated plastic strap, attach one end to a stud, have it run across the stud bay, wrapping it one full revolution around any cables it crosses, and then attach the other end to the other stud, fairly tight. Like a plumber would use on pipes. [Would be easier to do for 1 or 2 large SE cables, as opposed to 20 #12 or #14 NM cables.]

So would that comply with 334.30? Seems like it is a "strap . . .designed and installed so as not to damage the cable." Nothing in 334.30 requires a strap to be listed or even identified.

Cheers, Wayne

P.S. Obviously horizontal wood blocking and staples are the standard practice, just curious if the above would be a compliant alternative.
 
wwhitney said:
I guess my suggestion wasn't clear: I mean use a length of perforated plastic strap, attach one end to a stud, have it run across the stud bay, wrapping it one full revolution around any cables it crosses, and then attach the other end to the other stud, fairly tight. Like a plumber would use on pipes. [Would be easier to do for 1 or 2 large SE cables, as opposed to 20 #12 or #14 NM cables.]

So would that comply with 334.30? Seems like it is a "strap . . .designed and installed so as not to damage the cable." Nothing in 334.30 requires a strap to be listed or even identified.

Cheers, Wayne

P.S. Obviously horizontal wood blocking and staples are the standard practice, just curious if the above would be a compliant alternative.
Click to expand...
I hear you, I guess the hang up would be on "designed". You're right a "strap" doesn't need to be listed or identified, just needs to be "designed" for it. Does that mean the installer in the field says "hmmm, this should work" or does it mean there's a detail in the plans for that method of securing. If somebody went through the effort to secure it in such a manner and it was obviously well secured and protects the cable from damage I'd probably approve it, but I would wonder why they didn't just block it out.
 
Joe.B said:
I hear you, I guess the hang up would be on "designed". You're right a "strap" doesn't need to be listed or identified, just needs to be "designed" for it. Does that mean the installer in the field says "hmmm, this should work" or does it mean there's a detail in the plans for that method of securing. If somebody went through the effort to secure it in such a manner and it was obviously well secured and protects the cable from damage I'd probably approve it, but I would wonder why they didn't just block it out.
Click to expand...
I agree it's no biggie to put a 14.5 inch block of 2X between the studs and be done. Sounds like a butting of heads between the GC and Electrician.
 
Status
Not open for further replies.
Top