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

[jibber]

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

What constitutes a 4" bend? Can't that be obtained in a 2" LB. I have never been called on rear entry to a 200A box. When you come up from the ground with 2" conduit, you can't get into the house without going through a 2" LB. Are all entrances that come from underground conduit illegal?

I never even gave any of this a thought until it was brought up.... Hmmmmmmmm!

 

[iwire]

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

Jibber, you could use a larger LB in the middle of a run using reducing bushings.

But for house service you should be all set, all the 2" LB I can remember say 3 - 4/0s MAX in them.

This leaves me out of luck for 3 phase 4 wire feeders.

 

[jibber]

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

Bob, I agree! If it's a problem and none of the inspectors know about it, I'm going to let a "dead dog lie."

I wonder if there has ever been a genuine problem with that common bend, or if the guru's just thought it up in theory and decided to make it a code?

 

[russ]

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

OK richwaskowitz.

I'll concede the opening sentence to 312.6 says, conductors at terminals or conductors entering or leaving cabinets or cutout boxes and the like shall comply with 312.6(A) through(C).

 

[stew]

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

I hear what everyone seems to be saying here but then why do the manufacturers of a 200 amp panel knowing what wire size is to be used put a KO in the back center of the panel if it it against code to use it? My last install was done exactly as this post describes and I had a very picky inspector. He said nothing about my rear entry. I did not know that Ive been doing this wrong all these years. hmmmm???

 

[stew]

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

I hear what everyone seems to be saying here but then why do the manufacturers of a 200 amp panel knowing what wire size is to be used put a KO in the back center of the panel if it it against code to use it? My last install was done exactly as this post describes and I had a very picky inspector. He said nothing about my rear entry. I did not know that Ive been doing this wrong all these years. hmmmm???

 

[roger]

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

Stew,

I hear what everyone seems to be saying here but then why do the manufacturers of a 200 amp panel knowing what wire size is to be used put a KO in the back center of the panel if it it against code to use it?

the manufacturer would not know what we would feed the panel with, if copper conductors were used we could be within code.

Roger

 

[Ed MacLaren]

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

I wonder if there has ever been a genuine problem with that common bend, or if the guru's just thought it up in theory and decided to make it a code?

This may be another case of trying to legislate good workmanship. There are lots of electricians that could do this without creating any hazard, and I've seen some that would have a problem, even if the panel was 5" deep.

Ed

 

[stew]

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

Something about this rule just does not make sense to me. The location of the termination within the panel will remain within the same relationship to the rear entry regardless of how deep the box is methinks. The breaker or lugs will be in the same relative distance from the hole in the back even if the box was 4 or 5 inches deep. What iI am saying is you would be making the same relativley sharp bend down to the breaker or terminal regardless of the depth so how is having an extra 1/2 inch of depth going to make any difference to the installation?

 

[engy]

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

I'll be more clear.
As far as 312.6 in concerned, the panel could be 2" deep.
312.6 deals with gutter width not depth.

 

[stew]

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

engy .so if I understand you correctly the practice of coming in the back of the box and down to the terminal is ok?

 

[richwaskowitz]

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

We're not talking about 312.6, we're talking about 312.6(B)1 which happens to point to the same table that ALSO applies to 312.6.

 

[engy]

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

We're actually talking about 312.6(A), and I will concede.

 

[stew]

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

This issue has made me very curious as to the interpretations I see. So much so that I called the engineering dept at Square D to get further clarification. The Supervisory engineer Gary said the inspector should take a look at the note after table 312.6A. This note tells you how the bendining space is measured. In a direct line from the terminal to thewall barrier or obstruction. That means the distance to the front is not an issue only the distance measured in a straight line from the terminal to the TOP wall of the can which is the "obstruction" He said if the inspector wishes to conference call him with the electrician he would be more than happy to correct him. He saqys it meets code rquirements period!!

 

[iwire]

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

Stew if we go with that you are saying there is no minimum space required to bend the conductor?

Why is there a limit to how many 4/0s you can turn through a 2" LB?

The limit is three 4/0s through a 2" LB but a 2" EMT raceway can contain four 4/0s.

What do you think the limiting factor is here?

There are no terminals in the LB.

 

[stew]

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

no I am not saying you dont nreed bendinig space. The 4 " requirement is still there but the way it is determined is per the sub note specifically from the terminal in a direct line to the obstruction. Still need 4 " and of course there is alwaqys ample room from the terminal to the top of the can for this dimension to be obtained. never seen a panel that didnt have plenty of room to get this dimension.you still need the bending room but the dimension needed is not from the front of the can but in a direct line from the terminal to the obstrution which would be the top inside of your can.

[ March 04, 2004, 07:54 PM: Message edited by: stew ]

 

[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).

Sub note.

Note: Bending space at terminals shall be measured in a straight line from the end of the lug or wire connector (in the direction that the wire leaves the terminal) to the wall, barrier, or obstruction.

We are not talking about wire bending space at the terminals, we are talking about wire bending space between the front and rear of the enclosure.

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

In this case the obstruction is the front and rear of the panel not the terminals and wall of the panel.

Yes coming in from any side you will have enough space from the rear you will not.

[ March 04, 2004, 08:04 PM: Message edited by: iwire ]

 

[stew]

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

well sorry to say thats not how the square d engineering dept looks at it.Maybe they dont know whata they are talking about? They surely convinced me and are more thatn willing to discuss this with anyone who cares to.The table 312.6 A is the wire bending space at terminals is it not? confusining at best.

[ March 04, 2004, 08:47 PM: Message edited by: stew ]

 

[drg]

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

I have been reading this for a couple days and it sure is interesting , thought table 312.6(b) was used for minimum wire bending space at terminals ?

Im just trying to learn something here so don't mind me and please carry on.

John

 

[iwire]

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

Originally posted by stew:
well sorry to say thats not how the square d engineering dept looks at it.Maybe they don't know what they are talking about?

Maybe they did not understand the question.

Ask them if they provide enough wire bending space at the terminals and they answer correctly yes.

Ask them if they provide enough wire bending space to enter a 4/0 in the rear and they might answer differently.

Originally posted by stew:
The table 312.6 A is the wire bending space at terminals is it not?

Yes that is correct

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

This is two separate issues.

1)Minimum Wire-Bending Space at Terminals

2)Minimum Width of Wiring Gutters

The Note to Table 312.6(B) only applies to Wire-Bending Space at Terminals (read the first four words of the note) not to Width of Wiring Gutters

why do the manufacturers of a 200 amp panel knowing what wire size is to be used put a KO in the back center of the panel if it it against code to use it?

It is up to the electrician to use the equipment properly.

There are 17 KOs in a 4" square box, can we enter cables in each one?

[ March 04, 2004, 09:25 PM: Message edited by: iwire ]