4/0 cable into the back of a 3 1/2 inch deep panel

[stew]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

This person was also a code making pnael member as well as staff. And yes I know the rule and will follow it. Thanks Joe

 

[a.wayne3@verizon.net]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

Ok I`ll throw a wrench in the gears of the
longest thread i`ve seen here.A Milbank 320/400 rated meter can they are tiny feed these without overbending the CU wire

 

[websparky]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

The section on pull boxes is not applicable either becuase we are talking about a panelboard which is specifically adressede in 408.

Please read below and decide for yourself if the above statement is accurate.

2002NEC
ARTICLE 100 Definitions
Panelboard. A single panel or group of panel units designed for assembly in the form of a single panel, including buses and automatic overcurrent devices, and equipped with or without switches for the control of light, heat, or power circuits; designed to be placed in a cabinet or cutout box placed in or against a wall, partition, or other support; and accessible only from the front.

408.18 Enclosure.
Panelboards shall be mounted in cabinets, cutout boxes, or enclosures designed for the purpose and shall be dead-front.

ARTICLE 312 Cabinets, Cutout Boxes, and Meter Socket Enclosures
312.1 Scope.
This article covers the installation and construction specifications of cabinets, cutout boxes, and meter socket enclosures.

312.6 Deflection of Conductors.
Conductors at terminals or conductors entering or leaving cabinets or cutout boxes and the like shall comply with 312.6(A) through (C).

312.11 Spacing.
The spacing within cabinets and cutout boxes shall comply with 312.11(A) through (D).
(A) General. Spacing within cabinets and cutout boxes shall be sufficient to provide ample room for the distribution of wires and cables placed in them and for a separation between metal parts of devices and apparatus mounted within them as follows.

404.3 Enclosure.
(A) General. Switches and circuit breakers shall be of the externally operable type mounted in an enclosure listed for the intended use. The minimum wire-bending space at terminals and minimum gutter space provided in switch enclosures shall be as required in 312.6.

408.3 Support and Arrangement of Busbars and Conductors.
(F) Minimum Wire-Bending Space. The minimum wire-bending space at terminals and minimum gutter space provided in panelboards and switchboards shall be as required in 312.6.
Section 408.3(F) requires that installations in the field comply with 312.6. See also the commentary following 408.35, which covers the size of the enclosure.

408.35 Wire-Bending Space in Panelboards.
Exception No. 4: Either the top or the bottom wire-bending space, but not both, shall be permitted to be sized in accordance with Table 312.6(A) where there are no conductors terminated in that space.
(Handbook Comentary): Exception No.4 to 408.35 permits a reduction to the Table 312.6(A) spacing for the top or bottom space where no terminals face that space. In this case, the space is a gutter space, and measurement is on a line perpendicular to the wall of the enclosure and to the closest barrier post or side of a switch, fuse, or circuit breaker unit that is, or may be, installed.

430.97 Busbars and Conductors.(C) Minimum Wire-Bending Space. The minimum wire-bending space at the motor control center terminals and minimum gutter space shall be as required in Article 312.

(A) Width of Wiring Gutters. Conductors shall not be deflected within a cabinet or cutout box unless a gutter having a width in accordance with Table 312.6(A) is provided. Conductors in parallel in accordance with 310.4 shall be judged on the basis of the number of conductors in parallel.

Table 312.6(A) Minimum Wire-Bending Space at Terminals and Minimum Width of Wiring Gutters.

 

[don_resqcapt19]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

Stew,
I don't see any code making panel member from any panel who has listed his employeer as the NFPA. I don't think that paid staff are permitted to be members of a code making panel.
Don

 

[stew]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

408.35 Don I am sorry if I mistated his credentials. This person is a senior staff member of nfpa and has been with them for many many years. I am sorry I assumed he was a panel rep as he is the person I was instructed to send my correspondence to his attention for further didtribution I would assume to the proper person or persons.

web you are correct however you stil have not provided any statement in any of the articles which directly adresses panel DEPTH. 408.35 in its discussion specifically refers to top and bottom space, side space and gutter WIDTH not depth.The atricles mention having sufficient space to bend but only give a reference dimension that adresses top,bottom and width space and I still have not found any wording that mentions depth. This holds true for 430.97 as well. If you come up with something please let me know. I will try and get a cohesive question put together for the nfpa boys.

My contact with UL will continue as well.they are well represented on various panels. We need to specifically look at I believe UL 97 which is the specification for panelboards to see if this situation is adressed in there anywhere.

If nothing else this has been a very good learning experience as far as I am concerned eh?

[ March 13, 2004, 10:10 PM: Message edited by: stew ]

 

[macmikeman]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

Something has been totally overlooked here. If the exterior wall is constructed of 2x4" lumber, then we also have only 3.5 inches depth. The minimum bending radius of 4/0 ser cable is 5 times the diameter of the the cable measured from the center of cable. Whenever 4/0 ser cable is run down a 2/4" stud and then bent into the back of an exterior mounted meter socket, or on the other end - into the back of a surface mounted panel we get another code violation.
However I have also seen this done more times than I can count. My own preference is to have two subpanels, run 2 100 amp subfeed cables from the meter disconnect and use #2 ser cable. Its easier to install and pull thru holes.

 

[iwire]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

Stew I am totally baffled by this post by you.

you are correct however you stil have not provided any statement in any of the articles which directly adresses panel DEPTH. 408.35 in its discussion specifically refers to top and bottom space, side space and gutter WIDTH not depth.

Why would a wire need bending space in every other type of enclosure in any direction but not in a panel board front to back?

Here is the definition of 'width' from here Merriam-Webster Online Dictionary

Main Entry: width
Pronunciation: 'width, 'witth
Function: noun
Etymology: 1wide
1 : the horizontal measurement taken at right angles to the length

Front to back or left to right, both are horizontal measurements taken at right angles to the length.

[ March 14, 2004, 06:04 AM: Message edited by: iwire ]

 

[stew]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

Yes I can read. Depth (N) perpendicular measurement from the surface or horizontal measurement backward from the front. When I talked with nfpa he specifically said that the dimensions were not developed in the third dimension nor were they ever intended to be.

Condescending(adj) showing or implying patronizing descent from dignity or superiority.

Unless you have proof to the contrary I believe we are all pretty much equal in here and I am offended by your manner.

 

[iwire]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

Yes we are all equal here.

If you want, or need an official interpretation, get one.

Bob

 

[roger]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

Stew, I would also like to suggest you go ahead and ask for a formal interpretation so that we all might know the NFPA's official stance. (Assuming they will answer this)

That way the "I know so and so who says" can be left on the table.

Roger

 

[a.wayne3@verizon.net]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

Easy Bob.........

 

[drg]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

After reading the information here and going over and over the information in the NEC 2002 code book and the handbook I have came to my own conclusions,

One thing this whole subject emphasizes is that there are limits on how much bend is allowed on the wire going to terminals in enclosures, a obvious point, but one that keeps me pounding away at how they draw a conclusion of what we are reading here..... why is it this way.

from what I understand after days of off and on study is that table 312.6(A) is explaining a distance from the terminal to the enclosure wall measured in a straight line.( examples would be wire coming in from the sides or top and bottom of a panel.)

Table 312.6(B)is showing a straight line measured perpendicular from the direction of the wire leaving the termination point to the wall enclosure.( example would be coming through wall into back of panel)

So in my way of reading the code references, you would need no less that 6" distance measured in a straight line from the back of the panel to the lugs if you were to be using 4/0 wire, coming in from the back on the panel to the lugs ... table 312.6(B)would be used in this application.

This is strictly my view (opinion) on the subject.
John

 

[pierre]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

We could use an official interpretation.

Heres Mine: VIOLATION OF 312.6(A)

Pierre

 

[drg]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

It took me a couple days to come up with what I did, I was not ready for that curve ball....want to toss me that underhand .

 

[jibber]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

This is to whoever cares after all of this discussion:

Just had an inspection of a 2800 sq ft house in Snohomish county, Washington by the chief of electrical inspectors..........Passed with flying colors with a 2" LB coming into the rear of a 3.5" panel.

If there really is a problem, they will probably come out with a panel that fits 2x6 studs!

I think that this subj has been totally exhausted :roll:

 

[iwire]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

Originally posted by jibber:
Passed with flying colors with a 2" LB coming into the rear of a 3.5" panel.

I do not recall anyone saying that this is not done all the time and does not get picked up on.

That has little to do with it being a violation or not.

Originally posted by jibber:
If there really is a problem, they will probably come out with a panel that fits 2x6 studs!

They do, and I use them all the time, other than the panel at my home and some temp services I have not touched a 3.5" deep panel in years.

 

[pierre]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

Jibber
Did you bring to the 'chief' electrical inspector's attention our discussion of this subject? Not all inspectors know the whole code and never will. There are some issues that may go undetected for years such as this. I would be interested in what he has to say. Why don't you invite him to this thread.

Pierre

 

[jibber]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

Pierre, that's a good idea. I also would be curious as to his response.

 

[jibber]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

Bob, Me thinks that not everybody agrees with you as to whether it is a violation or not. There seems to be far more that don't than do, including many inspectors. What we need is some sort of ruling from the "official" body to really settle the matter as to the intent of the code.

 

[iwire]

Re: 4/0 cable into the back of a 3 1/2 inch deep panel

Originally posted by jibber:
Bob, Me thinks that not everybody agrees with you as to whether it is a violation or not. There seems to be far more that don't than do, including many inspectors.

I am fine with that, it is normal, I do not make my decisions based on majority rules.

I can sleep soundly knowing if I am wrong about this (and I may be ) that my error will not result in a violation.

If I happen to wire a 200 amp 3.5" panel from the back I will use 2/0 copper to avoid this issue, in case I get an inspector that sees it my way.

Originally posted by jibber:
What we need is some sort of ruling from the "official" body to really settle the matter as to the intent of the code.

As Don and Charlie pointed out there are set methods for this, unless your area has unusual rules the local inspector can not make "official interpretations"

[ March 17, 2004, 03:42 PM: Message edited by: iwire ]