Transitioning Wire from Interior 2x4 wall Through Back of Exterior Surface Mounted Panel

[LarryFine]

Charlie's Rule of Technical Reading:

It doesn't say what you think it says, nor what you remember it to have said, nor what you were told that it says, and certainly not what you want it to say, and if by chance you are its author, it doesn't say what you intended it to say. Then what does it say? It says what it says. So if you want to know what it says, stop trying to remember what it says, and don't ask anyone else. Go back and read it, and pay attention as though you were reading it for the first time.

Copyright 2005, Charles E. Beck, P.E., Seattle, WA

 

[packersparky]

312.5(C) doesn't have any requirement about using a listed product.

Cheers, Wayne

Doesn't 334.6 apply though?

 

[ESolar]

For the rear entry to the box I am using a galvanized rigid close nipple with two sealer locknuts and an insulated bushing on the interior of the box. Close nipple goes through wall. In the wall (which is currently accessible) I am just using a strap and a bushing on the open end of the close nipple. Any issues there?

 

[tortuga]

For the rear entry to the box I am using a galvanized rigid close nipple with two sealer locknuts and an insulated bushing on the interior of the box. Close nipple goes through wall. In the wall (which is currently accessible) I am just using a strap and a bushing on the open end of the close nipple. Any issues there?

As others mentioned 312.5(C)

 

[packersparky]

312.5(C) also only allows entry through the top of the enclosure, not the back. Here is the entire exception from the 2020 NEC.

(C) Cables
Where cable is used, each cable shall be secured to the cabinet, cutout box, or meter socket enclosure.
Exception No. 1: Cables with entirely nonmetallic sheaths shall be permitted to enter the top of a surface-mounted enclosure through one or more nonflexible raceways not less than 450 mm (18 in.) and not more than 3.0 m (10 ft) in length, provided all of the following conditions are met:

1. Each cable is fastened within 300 mm (12 in.), measured along the sheath, of the outer end of the raceway.
2. The raceway extends directly above the enclosure and does not penetrate a structural ceiling.
3. A fitting is provided on each end of the raceway to protect the cable(s) from abrasion and the fittings remain accessible after installation.
4. The raceway is sealed or plugged at the outer end using approved means so as to prevent access to the enclosure through the raceway.
5. The cable sheath is continuous through the raceway and extends into the enclosure beyond the fitting not less than 6 mm (1/4 in.).
6. The raceway is fastened at its outer end and at other points in accordance with the applicable article.
7. Where installed as conduit or tubing, the cable fill does not exceed the amount that would be permitted for complete conduit or tubing systems by Table 1 of Chapter 9 of this Code and all applicable notes thereto. Note 2 to the tables in Chapter 9 does not apply to this condition.

 

[tortuga]

312.5(C) also only allows entry through the top of the enclosure, not the back. Here is the entire exception from the 2020 NEC.

Well the 312.(C) exception does, but 312(C) just says if you go in the back you have to secure each cable to the panel, with as you pointed out a listed connector.
I think Dennis had some proposed changes to this years back and the reason the CMP says is arc blast can jet thru a short nipple into the wall.
If you hit a jbox first then your not a cable anymore your a raceway.

 

[tortuga]

I use these on occasion, they are made by bridgeport;

 

[ESolar]

Doesn't 334.6 apply though?

I think that you are correct. But it appears to allow for listed cable ties and non-listed straps, hangers or similar. However, it's not difficult to find listed "fittings". It would make sense to epoxy those to the interior of a NEMA 3 box, versus penetrating the box with a screw. But it's unlikely that epoxy is a listed means of securing any of the listed straps and ties. My approach is to epoxy a small raised metal bar to the box and to which listed ties can be screwed.

"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, at intervals not exceeding 1.4 m (41/2 ft) and within 300 mm (12 in.) of every cable entry into enclosures such as outlet boxes, junction boxes, cabinets, or fittings. The cable length between the cable entry and the closest cable support shall not exceed 450 mm (18 in.). Flat cables shall not be stapled on edge."

 

[packersparky]

I think that you are correct. But it appears to allow for listed cable ties and non-listed straps, hangers or similar. However, it's not difficult to find listed "fittings". It would make sense to epoxy those to the interior of a NEMA 3 box, versus penetrating the box with a screw. But it's unlikely that epoxy is a listed means of securing any of the listed straps and ties. My approach is to epoxy a small raised metal bar to the box and to which listed ties can be screwed.

"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, at intervals not exceeding 1.4 m (41/2 ft) and within 300 mm (12 in.) of every cable entry into enclosures such as outlet boxes, junction boxes, cabinets, or fittings. The cable length between the cable entry and the closest cable support shall not exceed 450 mm (18 in.). Flat cables shall not be stapled on edge."

I think you still have a problem with (2.) in the exception. "directly above the enclosure"

 

[ESolar]

As others mentioned 312.5(C)

Charlie's Rule: It does not say that you cannot go through the back and it does not say that you have to go through the top. It says that the cable must be secured - that is the rule. Then there is an exception to rule of securing the cable to the box. That exception is to go through the top - then you do not have to secure cable to the box, but you have to satisfy a bunch of other requirements. That is the way that it reads.

 

[SSDriver]

I think it's insane we can run a conduit as a chase above the panel on a surface mount installation and not on a flush mount installation. If you follow all the same rules what additional danger is there?. Complete BS.

 

[packersparky]

Charlie's Rule: It does not say that you cannot go through the back. It says that the cable must be secured - that is the rule. The exception to rule, securing the cable to the box, is an exception - and that is go through the top - then you do not have to secure to the box. That is the way that it reads.

Yes it does. Look at post #25 and post #29.

 

[tortuga]

The intent of 312.5(C) is to contain arc blast in a panel, Here is the code change proposal it was from back in '08 I use it in a class:

This 2008 proposal accurately describes what we commonly see:
Submitter: Lanny G. McMahill, Phoenix, AZ
Recommendation: Add new Exception.
Exception: Cables with entirely nonmetallic sheaths shall be permitted to
enter the back of a surface-mounted enclosure through one or more nonflexible
raceways not more than 75 mm (3 in.) in diameter, and not less than 75 mm (3
in.) and not more than 600 mm (24 in.) in length, provided all of the following
conditions are met:
(a) Each cable is fastened within 200 mm (8 in.), measured along the sheath,
of the outer end of the raceway.
(b) The raceway extends directly into an enclosed wall space.
(c) A fitting is provided on each end of the raceway to protect the cable(s)
from abrasion.
(d) The raceway is sealed or plugged at the inner end using approved means
so as to prevent access to the enclosure through the raceway.
(e) The cable sheath is continuous through the raceway and extends into the
enclosure beyond the fitting not less than 50 mm (2 in.).
(f) The raceway is fastened at its outer end in accordance with the applicable
article.
(g) The conductor size is maximum 10 AWG.
(h) The raceway shall be permitted to be filled to 60 percent of its total crosssectional area, and 310.15(B)(2)(a) adjustment factors need not apply to this
condition.
Substantiation: This is a standard wiring practice allowed in many
jurisdictions for the past 30 years. This is a safe and reasonable wiring practice
for surface mounted enclosures. This proposal is intended to modify the
practice. The proposed language is intended to mirror the current exception;
yet, it incorporates more restrictions and clarification. The current exception
allows Type NM cables to enter a raceway in the top of a surface mounted
enclosure. This exception allows Type NM cables to enter a raceway in the
back of a surface mounted enclosure. Additional restrictions include:
1) The raceway is limited to a maximum 3 inches in diameter, and restricted
to between 3 inches and 24 inches in length. The 3 inches in diameter is to
restrict the size of the opening in the back of the enclosure. The minimum
length is to ensure that the raceway extends into the wall space. The maximum
length is to allow for greater depth of wall and additional flexibility in
installation.
2) The cable must be fastened within 8 inches of the raceway end. This
mirrors the requirement noted in 314.17(C)1 Exception. It also allows for better
securing of the cables.
3) The raceway must extend into an enclosed wall space. This is intended to
prevent access to the cables and provide a degree of protction from access to
the enclosure.
4) The raceway must be sealed or pluged at the inner end to prevent access.
5) The cable sheath must extend at least 2 inches into the enclosure. The
current exception only requires 1/4 inch.
6) The conductor size is restricted to 10 AWG. This is to prevent larger
cables from entering the opening.
7) The raceway is restricted to 60 percent fill and adjustment factors need not
apply.

Panel Meeting Action: Reject
Panel Statement: The use of short fittings as described is a potential hazard,
because an arc in the panel may no longer be contained by the enclosure.
CMP-9 has discussed this approach repeatedly over many cycles, and does not
agree that it should be allowed.

“one of the most surprisingly controversial, passionately debated, and

exhaustively studied topics in the history of CMP 9” -- Frederic P. Hartwell Code making Panel 9 member.

 

[ESolar]

Yes it does. Look at post #25 and post #29.

I disagree. The rule is: "
(C) Cables
Where cable is used, each cable shall be secured to the cabinet, cutout box, or meter socket enclosure."
Everything after the rule is the exception to the rule, including requirement 2 of the exception that you reference. One does not need to meet the requirements of the exception to the rule if they follow the rule and secure the cable to the box. The rule applies to interior boxes as well. So by your reasoning, an entrance through the bottom in an interior box would also be noncompliant - imagine.

 

[ESolar]

The intent of 312.5(C) is to contain arc blast in a panel, Here is the code change proposal it was from back in '08 I use it in a class:

That speaks for itself - and so does the current 312.5(C). As I read it, regardless of its intent, it currently allows for rear entry with securing the cables to the box. But now I am nevertheless concerned about the unlikely arc blast issue that the experts reference. Perhaps the close nipple should terminate in a J Box in the wall to provide some protection.

Do you know why they proposed to limit the conductors to 10 AWG?

 

[tortuga]

Perhaps the close nipple should terminate in a J Box in the wall to provide some protection.

Yeah thats what I do, then your no longer are 'cable' going in the panel, its a complete raceway.

Do you know why they proposed to limit the conductors to 10 AWG?

To keep the opening into the stud wall as small as possible.

 

[wwhitney]

312.5(C) just says if you go in the back you have to secure each cable to the panel,

Precisely.

with as you pointed out a listed connector.

No, that requirement is not in 312.5(C)!

Cheers, Wayne

 

[wwhitney]

Doesn't 334.6 apply though?

It does, and it requires fittings "associated" to NM to be listed. The definition of "fittings" seems to cover means of support like staples, cable ties, straps, connectors, etc. So under the broadest reading of 334.6, every staple you use to secure NM has to be listed, because it is an associated fitting.

But then we 334.30, which says: "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 suggests in passing that "straps and hangers" are fittings (without explicitly saying so), but that staples and cable ties are not (by breaking them out separately).

So apparently you can use an unlisted staple or a listed strap to secure your NM cable. But if you use plumber's tape (that perforated plastic strap), that's a violation of 334.6? That's what it implies, although it doesn't quite say it directly. Seems like a very nit-picky interpretation.

Also, the second half of 334.30 is the limiter "at intervals not exceeding 1.4 m (41∕2 ft) and within 300 mm (12 in.) of every cable entry into enclosures . . ." So 334.30 is not in fact limiting all means of support and securement of NM cable to the specified list; it's just saying that you have to use those one of those means of support and securement at the specified frequency. Other points of support/securement, such as required by 312.5(C), are not subject to the list in 334.30.

Cheers, Wayne

 

[wwhitney]

Yeah thats what I do, then your no longer are 'cable' going in the panel, its a complete raceway.

Yet 312.5(C) seems to lack an exception for cables in raceway wiring methods. I should probably submit a PI for 2026.

Cheers, Wayne

 

[letgomywago]

The intent of 312.5(C) is to contain arc blast in a panel, Here is the code change proposal it was from back in '08 I use it in a class:

I wonder if there would be a way to get the exception to allow for 18 inches of raceway from any direction in the panel not just the top of a panel. This would allow for the uncommon but still possible icf house with an outdoor panel, double stud exterior wall, or having the cables kick up through an interior wall that's deep enough like how they do frost free spouts with the loop of pex. I think having the exception allowed for any direction of 18inches of conduit would make things simpler for these odd situations and still provide for some relief while still being safe.

With the interior wall method like frost free spigot home runs could be run down a closet wall and a access panel could be on the inside of the closet if the inspector enforced that the entry to the raceway of the romex be accessible.