Wire bending space within a panelboard. 312.6 (A)?

[richwaskowitz]

I am looking for the applicable Code reference which would dictate the dimension needed with respect to the depth of a panelboard (a breaker panel, specifically) needed when entering into the back of said panelboard and the conductors are 4/0. In other words, if one were to come in through the back of a flush-mounted panel which is only 3 1/2 inches deep and try to make that tight 90 degree bend to route the conductors through the panel to the main breaker, what determines the minimum dimension required? I thought is was 312.6 (A) but that is referring to wiring gutters within cabinets or cutout boxes and I am not quite sure if that applies to my situation. After all the table is titled "space at terminals AND width of wiring gutters". That table says 4 inches. If the panel is 3 1/2 deep, I say you can't come in through the back in this case. Please tell me if I am applying the correct reference.

 

[Smart $]

408.55 is the appropriate section... but it sends you back to 312.6 for dimensions.

408.55 Wire-Bending Space Within an Enclosure Containing
a Panelboard.


(A) Top and BottomWire-Bending Space. The enclosure
for a panelboard shall have the top and bottom wirebending
space sized in accordance with Table 312.6(B) for
the largest conductor entering or leaving the enclosure.

Exception No. 1: Either the top or bottom wire-bending
space shall be permitted to be sized in accordance with
Table 312.6(A) for a panelboard rated 225 amperes or less
and designed to contain not over 42 overcurrent devices.
For the purposes of this exception, a 2-pole or a 3-pole
circuit breaker shall be considered as two or three overcurrent
devices, respectively.

Exception No. 2: Either the top or bottom wire-bending
space for any panelboard shall be permitted to be sized in
accordance with Table 312.6(A) where at least one side
wire-bending space is sized in accordance with Table
312.6(B) for the largest conductor to be terminated in any
side wire-bending space.

Exception No. 3: The top and bottom wire-bending space
shall be permitted to be sized in accordance with Table
312.6(A) spacings if the panelboard is designed and constructed
for wiring using only a single 90-degree bend for
each conductor, including the grounded circuit conductor,
and the wiring diagram shows and specifies the method of
wiring that shall be used.

Exception No. 4: Either the top or the bottomwirebending
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.

(B) Side Wire-Bending Space. Side wire-bending space
shall be in accordance with Table 312.6(A) for the largest
conductor to be terminated in that space.

(C) BackWire-Bending Space. Where a raceway or cable
entry is in the wall of the enclosure opposite a removable
cover, the distance from that wall to the cover shall be
permitted to comply with the distance required for one wire
per terminal in Table 312.6(A). The distance between the
center of the rear entry and the nearest termination for the
entering conductors shall not be less than the distance given
in Table 312.6(B).

 

[richwaskowitz]

Doggonit. Why did I not think to look in the specific article? Thanks. Is there any reason the same requirements would NOT apply if it were a meter base or outdoor main disconnect i was talking about? I may be inheriting (fixing) an installation where some guy mounted a 200 A service disconnect on the siding next to the existing meter, exited the back of the 3 1/2 inch deep disconnect (first mistake) into the exterior wall then bent the 4/0 subfeeder cable within the confines of a 2 x4 wall (second mistake) and then went up the wall into the attic. I have not figured out quite how to fix the bend into the stud cavity yet. According to 338.24, a 7.5 inch radius is needed for a cable 1 1/2 inches in diameter, not the 1/2 inch radius there now.......

 

[GoldDigger]

You could use a non-buried junction box and change direction with a terminal block inside the box if you could find one with a right angle.
That way neither conductor passes through the box.

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