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

[websparky]

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

Hi Guys,

Table 312.6(A) is the correct table to use in this installation.

This is from the Handbook;

Section 312.6(B)(2) and Table 312.6(B) provide the requirements for wire-bending space where straight-in wiring or offset (double bends) is employed at terminals. Section 312.6(B)(1) applies only to 90 degree bends.

Note that in accordance with the notes to Tables 312.6(A) and 312.6(B), when using Table 312.6(A), bending space is measured in the direction in which the wire leaves the terminal, and when using Table 312.6(B), it is measured in a direction perpendicular to the enclosure wall.

 

[drg]

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

Bob, its a good thing that you take time to explain stuff like this , I would never begin to understand reasoning like this and just go by these things while reading a book and it seems like issues similar to this are avoided out in the field and getting help can be difficult at times because of many different reasons.

Thanks for your efforts, you make a difference.
John

Im still not saying that I understand all this stuff but at the least its making me aware of how involved this business is and how little I really know.

 

[pierre]

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

Stew
Would you mind posting the number you used to call SqD?

Pierre

 

[stew]

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

iwire I made it perfectly clear as to what I was describing. A center rear entrance, a 90 degree bend,a 4/0 al conductor, and a termination at the breaker. Could not have been more clear.

[ March 05, 2004, 12:59 AM: Message edited by: stew ]

 

[stew]

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

for pierre or anyone else who cares: Square d tech service line is 888-778-2733. Ask for tech service and when you get there ask for gary the engineering supervisor. I used my firm name of s&s Repair when I spoke with him today.I was on a conference cal with a gal from tech service and one of garys engineers . I was very precise in my description of the situataion.He was equally as precise in notining the foot note and explaining how the dimension is arrived at and applied.I dont wish to be argumentitive however they should be the experts when it comes to engineering thier products to comply with current code. They were very helpfull and will discuss this further with anyone who wishes.

 

[iwire]

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

Originally posted by drg:
Bob, its a good thing that you take time to explain stuff like this , I would never begin to understand reasoning like this and just go by these things while reading a book and

John that is very kind of you, but I urge you to always verify things you read on the Internet on your own also, I have been, and will be again mistaken.

I try to provide references to my posts so anyone can see where I come up with my opinion on something, and when needed tell me I am wrong.

 

[iwire]

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

Originally posted by stew:
I dont wish to be argumentitive

Stew, I don't think your being argumentative, we just see this differently and you may teach me something, I can be a stubborn PITA.

Originally posted by stew:
however they should be the experts when it comes to engineering their products to comply with current code.

Yes and even if I am correct in my interpretation they have still engineered their product to comply with the NEC and UL.

There are countless ways to make a panel that was built to be code compliant non-code compliant.

Again it is up to the installer to use the equipment correctly.

We are talking about a 200 amp panel, the lugs on a 200 amp panel are typically large enough to handle 250 kcmil, if I chose to use 250 kcmil and use 250 amp OCP is that a violation?

Would that violation be the result of a incorrect design or from a incorrect installation?

Originally posted by stew:
They were very helpfull and will discuss this further with anyone who wishes.

It sounds like Pierre is going to give them a call, I will be interested in what he hears from them.

Bob

 

[richwaskowitz]

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

Wow! What a hornet's nest I've stirred up.

I just talked to Gary at Sq-D and he plead the fifth, and is referring me to their code compliance guys and I await their call back.

I will definitely post their position.

 

[jii]

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

Hi guys, this a great thread. My 2 cents on this is that 312.6 never talks about depth, only Width of Wiring Gutters [312.6(A)] and Wire-Bending Space at Terminals[312.6(B)], so to add depth requirements is not the intent of the NEC. Regarding the Max. size & number of conductors marked on condulets,this is coverd by 314.28 .In general with pull & jouction boxes & condulets, with conductors size #4 and over should be 8X for straight and 6X for anngle pulls.But 314.28(A)(3) allows for smaller dimentions if the condulet is listed & permanently marked with Max.size and number of conductors. P.S. this is a great forum.

 

[richwaskowitz]

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

JII... I am the guy that started this whole mess. Please explain why you think this is not a wire bending issue. My point (and that of the instructor that pointed this out to me) is that the 3.5 inch depth where the conductors enter the enclosure is not sufficient to deflect (bend) the 4/0 to get them into the lugs of the main breaker. If 312.6(b)1 is not the limiting factor in this situatution, what is? Regardless of how much room is available left to right and top to bottom in the space above the breaker, you must bend those 4/0's within the confines of that 3.5 depth in order to get them into the lugs. That is the intent of 312.6(b)1 is it not?

 

[jii]

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

I could be wrong, but I believe the intent is to give you enough room at the lugs.As you said, but whats to say if you enter the enclosure threw the back far away from the lugs,then rout them around the enclosure to the lugs. As long as you have the required bending space from your lugs to the wall ,barrier,or obstruction.[Table 312.6(A)Note]you meet NEC requirements.
As far as Min. bending radius for under 600 Volt conductors I don't know of any :roll: , over 600V its 300.34

 

[stew]

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

jii I think you nailed it.

 

[jii]

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

Something else I forgot to say.Is that if this enclosure was a pull,junction box,or conduit bodie,you would use Table 312.6(A) as stated in 314.28(A)(2)Exc..But were talking about cabinets,cutout boxes,& meter socket enclosures. John II

 

[pierre]

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

I spoke to Pierce from SqD today. He listened intently to the question and then put me on hold to confer with his associates. His response is that they design their enclosures for panelboard installations to UL 50. The bending radius they meet is for, top - side and bottom, not from the back of the enclosure. He thought that from the back it would not meet the bending radius for 4/0 based on a 3 1/2 inch depth enclosure.

I also spoke with Brian McPartland, who I consider one of the nations top code experts. He said almost the same thing as Pierce.

I personnally say that the installation of 4/0 from the back wall of the enclosure to lugs directly below is not permitted - 4 inches is 4 inches.

Pierre

 

[stew]

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

pierre where in the code is the bending radius of 4/0 discussed?

 

[pierre]

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

Table 312.6(A).
The first column on the left is the conductor size.
The next column under 1 is for one conductor per lug and the inch column is the column referenced. Reading across from 4/0 to 4 inches. The enclosure is only 3 1/2 inches in depth.

Reading 312.6(B)(1) refers one back to table 312.6(A) if the conductor does not enter leave through the wall opposite its terminal. That is the example of this thread.

Pierre

 

[luke warmwater]

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

Pierre,
I am not familiar with the QO panels to that extent (as far as where the knockout is located).

The CH panels have the rear knockouts located in the upper left back and the upper right back (could be lower if panel is inverted).

Are you saying that the CH would be OK to enter since the KO is not directly above the main breaker?

 

[websparky]

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

Hi Guys,

Let me see if I can state 312.6 in a clearer manner when it refers to the
minimum bending radius of a conductor when no terminations are involved.

312.6 covers "Deflection of Conductors." Deflection means "bending".
It starts off by giving us 2 distinct references.
(1)Conductors at terminals.
(2)Conductors entering or leaving cabinets (or cutout boxes and the like).

Then, it goes on to state that this is mandatory rule,
"shall comply with 312.6(A) through (C)."

This next reference relates to (2) above.
Conductors shall not be deflected (bent) within a cabinet or cutout box
unless the enclosure has enough room to safely bend the conductor
in accordance with Table 312.6(A).
The distance from the point of entrance to the nearest and opposite
wall of the enclosure where the bend will take place is listed in the table below.

 

[ronaldrc]

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

If this is true where can I find a 4" deep 2" LB. wouldn't this apply here to?

 

[don_resqcapt19]

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

Ron,
Yes, Table 312.6(A) applies to conduit bodies. See 314.28(A)(2) and its exception. Note that without the exception the 2" LB would have to be at least 12" deep.
Don

[ March 05, 2004, 08:51 PM: Message edited by: don_resqcapt19 ]