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

[richwaskowitz]

How many of you have ever run 200 amp service entrance cable (4/0 AL) in through the back of a standard main panel (3 1/2 inches deep)? It is my understanding that this is in violation of the minimum wire bending space provision of 373-6 (1999) where it states that 4/0 requires 4 inches of bending space.

 

[ccha9219]

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

The way I read it that pertains to bending space at lugs and width...not depth, of wiring gutters and or cabinets.
I do agree that's not much space for 4/0 it
isn' against code

 

[iwire]

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

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).

Back, sides, top or bottom you must have the room to bend the conductor.

4/0 in the back of a 3 1/2" deep panel is not OK.

 

[drmoody]

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

This is section 312.6 in the 2002 code. Article 312.6(B)(1) is a section pertaining to conductors that do not enter the wall opposite their terminals. The way I read it, a 4/0 conductor entering through the back (which is an adjacent wall and not opposite) will not meet the minimum gutter requirement of 4" in a 3.5" panel as determined by table 312.6(A). Therefore, not permitted because of deflection of the conductors.

 

[richwaskowitz]

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

I agree that this may not be done. I heard this at a code up-date course a few years back. My question is, how many of us do not / did not know this? This post was really intended to be an informational one rather than a question.

 

[a.wayne3@verizon.net]

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

We did mmmmmmm 2,000 homes last years and we bid back to back 200`s .So probably we did 1,800 of these 200 4/0 AL services

 

[iwire]

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

And.....

 

[wmeek]

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

So according to 312 is 3/0 also required to have 4". Therefore it can not come into a 3 1/2 " box from the back side.

 

[iwire]

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

This is the same reason you will see LBs marked with a maximum number of large conductors.

You may have 4 - 4/0s in a 2" raceway but you will not be able to turn them through a standard LB.

 

[richwaskowitz]

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

So, Awayne3, what are you saying? That there is no violation or that there is?

 

[paul32]

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

What's the advantage of bringing in the conductors in the back of the panel vs. the top?

In our house the PVC is run through the block foundation to into the back of the panel. Seems like it would be easier to run it through the wood and come into the top of the panel.

 

[richwaskowitz]

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

I'm not saying that there is any advantage. I am just saying that once I did have an installation where the headroom was limited and the cable came through in such a way that I did not have room to drop down into the top or turn into the side but entered through the back of the panel. I have since been informed during a code update course that that was a boo-boo. The point of this post was to find out how many others have been doing the same without being aware of the violation and at the same time educate all who read this so they can benefit.

 

[pierre]

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

Ignorance is Bliss (not Hbliss )
I have in the past performed this type of installation before. I was never aware of this table in the past, and never even thought to apply it to this installation...

It is interesting, because until today I have not thought about it, but now I see it is clearly not permitted.
How does one go about and tell the 1000 or so contractors in this area that this is a violation, when the past 60 years it has been permitted?
This is a fairly common type of installation practice here

Pierre

 

[paul32]

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

I assumed there was an advantage because this post indicates entering the back is common. I can see the reason if no room to do anything else, but in new construction when you could enter from the top or the back, why would you enter the back, in a basement? I could also see that in the case where the meter is directly behind the panel in a garage you would enter from the back. In my basement, the slope of the ground means the entrance into the basement is not buried. It seems like it could have entered the basement through the wood instead of the block, which would be easier, so is there some benefit to the extra trouble to drill through the concrete block to enter the panel in the back?

 

[ccha9219]

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

I have re-read 312. I Have done hundreds of back to back services with 4/0 Al. Never faild an ispection.
Maybe the local inspector should re-read it also.

 

[a.wayne3@verizon.net]

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

Paul 32 there are no basements in florida... Not unless you up by the Georgia border.We use this installation all the time to cite radius bend as a violation..Come ON !!!!!!!!!I have a good one the AHJ here have cited 300 4 d for nm going into the trusses without 1 1/4 clearance from the top
of the furring along top of block wall into trusses.So we have to use plumbers kick plates where we penetrate the furring into the attic.sure the chances of being damaged by ceiling rock board hitting the nm against the block is minimal but hey it is a code and we have to comply so what if the drywall bulges.Any thoughts ???????? Allen.

 

[paul32]

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

I didn't see anything in this thread about Florida.
I'm in Minnesota.

 

[engy]

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

I think the first response was correct.
Read the note at the bottom of table 312.6(A)

 

[russ]

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

I always thought this code ment you had to have (in this case) 4" of space straight out of the lug before the wire had to be bent.
This would stop people from bending small 90s in the wire.

 

[richwaskowitz]

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

Don't think so Russ.... This subject was beat up pretty good during a code update course I took for master license renewal in Michigan. The instructor was pointing to this very practice as an examlpe of how easy it is to overlook something like this wire bending requirement. It was his (expert) opinion that since most common breaker panels were 3.5 inches deep to fit into stud walls, that there was not sufficient wire bending space for 4/0 (typical for aluminum 200 amp entrance cable) when the cable entered from the back of the enclosure. He cited 312.6(B)1 specifically. What I would like, would be to hear from some inspectors that would concur or disagree with that instructor. With due respect to the others who have replied here, hearing that they have installed quantities of panels under these cirumstances does not in and of itself prove to me that it is not a violation.