all branch circuits go into panel via 2" PVC, 310.15(B)(3)(a) issue ?

RustyShackleford

Senior Member
Location
NC
Another issue is space in the panel - for wire bending, add'l ground bar, and such. Check this screen-grab from the Siemens catalog. Note for the 30-space/48-circuit boxes, the "outside" version is 5" taller, whereas the "inside" versions fits 10 more "spaces" (5" vertically) into the same 30" height as the older-generation 20-space/40-circuit boxes. ( I'd be tempted to use the outside box even if this were an indoor situation).

Also tempted to put the new box "upside-down" so the ground bars are close to where the branch-circuit conductors enter. Assuming there are code-compliant ways to transition from the 2" or 2-1/2" PVC conduit to the hub cutout at the breaker end of the panel.
 

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AC\DC

Senior Member
Location
Florence,Oregon,Lane
Occupation
EC
The linked page says "up to 2 NM cables at one time." Did it say 3 when you posted it earlier this month?
Weird I know they have one that does 3
Wrong link
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
Take a look at Arlington NM841-NM844
Bad URL, your search terms were not embedded in the URL. Try these links, in increasing order of KO size, from 1/2" to 1-1/4":


Cheers, Wayne
 

AC\DC

Senior Member
Location
Florence,Oregon,Lane
Occupation
EC
I have used them, only problem with them is on 3r pvc box’s when I transition from nmb to thwn the boxes thinkness does not allow those to be used have to use 2 screws with long throats
 

Amps

Electrical Contractor
Location
New Jersey
Occupation
Electrical, Security, Networks and Everything Else.
That's a lot of splicing. Are you using wire nuts or wagos?
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
If your under the 2020 NEC you could add tiny section of cable tray in the crawl space. Per the new exception 2.
In reality the intent of 312.5(C) is to prevent someone from putting a close chase or PVC adapter in the panel and pulling all the romexes thru.
And then if there is a catastrophic bolted fault failure in the panel (typically a service) all that vaporized copper and aluminum jets into the hole.

Could it be also be argued that once the 2" PVC conduit run is over 24" long, and now your doing a chapter 9 fill calc and de-rating, its now the PVC 'wiring method' attaching to the 'cabinet' from the point of view of 312.5(C)? And since NC has that exemption your fine outdoors up to 6 feet or whatever.
 
I don't think the securing is that necessary
334.30
(B) Unsupported Cables. Nonmetallic-sheathed cable shall be permitted to be unsupported where the cable:
(1)
Is fished between access points through concealed spaces in finished buildings or structures and supporting is impracticable.

always remember the guys writing all this code are not the brightest bulbs in the drawer, sometimes we have to use common sense. You'd be hard pressed to find a situation that this type of install has killed someone. At least your upgrading the panel, sometimes you can't fix everything.
 
I'm just saying, when it's a remodel situation, do the best you can within reason, when THHN enters a cabinet it is not secured. So even though it's written like that, sometimes it doesn't make sense. Obviously on a new install you would secure it. My inspectors here in Arizona have told me to just do the best you can, it's better than it was.
 

Mr. Serious

Member
Location
Oklahoma, USA
Occupation
Electrical Contractor
I like the idea of stripping back the NM, even though technically it's not allowed because that inner wire is "similar to THHN/THWN" but is not listed. Run all the NM circuits into a 12x12 junction box in the attic, strip everything back and put a ground bar in the box, and take a 2" PVC out the back, through the end wall of the house, and down into the side of the panel (with LBs at top and bottom). Run all circuit conductors and one main grounding wire down into the panel through the 2".

I like the idea, but I don't think I will try it and see what the inspector says. I'm on shaky ground in Tulsa because I've only done three jobs there, and two of them were managed by an acquaintance who doesn't have a license but was running the jobs under my license, and he screwed up the last one and I had to get it re-inspected after he fixed it.
 
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