312.8 confusion!

Merry Christmas
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davedottcom said:
LOL
I was already confused!;)

I guess I'm still confused about where exactly to measure from.
The "side" of the enclosure to the internal equipment
or
from the "Knock out" entrance to the equipment.

I came in the back and went out the side!?:confused:
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You measure vertically from the bottom inside of the enclosure to the bottom-most part of the guts (usually the insulating barriers of the load-side terminals... then multiply that times the internal depth [of the bottom] of the enclosure, including any internal cavity in the cover.

If the depth is 6" and you need ~0.9in^2 ? 40% (2.25in^2) the "gutter" width has to be at least 3/8 in.

Offhand I'd say you are beyond marginally safe :grin:
 
I don't have time for math, but here's how I see it easiest done:

(L ? W ? D of Can) - (L ? W ? D of breaker space) = Available Space

(Square inches of conductor ? length ) = Used space
 
georgestolz said:
I don't have time for math, but here's how I see it easiest done:

(L ? W ? D of Can) - (L ? W ? D of breaker space) = Available Space

(Square inches of conductor ? length ) = Used space
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While the volume method you and BryanMD bring up would seem to be sufficient, it has one major flaw: It averages the cross-sectional area of the wire space. Typically, disconnects and panelboards have less wire space to the sides than at the top and bottom. The requirement specifies using cross sectional area.
 
Smart $ said:
While the volume method you and BryanMD bring up would seem to be sufficient, it has one major flaw: It averages the cross-sectional area of the wire space. Typically, disconnects and panelboards have less wire space to the sides than at the top and bottom. The requirement specifies using cross sectional area.
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Not sure about the others but *my* intent was to get the OP to think deeper about the question by looking at it differently. Once he understands the principle involved he should be able to apply it (to this or similar/future questions).
 
Try picturing it this way in your mind.

Imagine that you laid the panel in a metal saw and cut thru it diagonally (90 degree) at the points where the conductors pass thru that particular (wire) space.

If you looked directly at the end of the panel, you would see the wire space and the amount of wire fill in that particular space.

If the conductors exceeded 40% of the area of that space at any point, it is overfilled.....non compliant.

Just my 2 cents.

steve
 
davedottcom said:
But I would have to add a 3rd dimension (Heigth)to account for that???
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No, the same way the length of a conduit does not affect the cross-sectional area fill limitations (other than the 24" nipple exception). Adding the third dimension gives you volume, not area.
 
davedottcom said:
I guess I'm still confused about where exactly to measure from.
Click to expand...
The space you're using as a wireway is horizontally across the enclosure bottom area, so you'd measure from the bottom of the enclosure to the bottom of the 'guts' multiplied by the depth of that space, from the enclosure cover to the rear surface.

In other words, as if you had X-ray vision, look at the enclosure from one side, not the front. The height is from guts to bottom, and the width is from cover to rear of the enclosure. The 'length' of that space is the enclosure width, not of concern here.

Added: Think of this space as a big LB, and you need to determine the cross-sectional area of the body of the LB.
 
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Dave,
I think Russ also has a good point here...314.28(A)(2) applies and is more likely to be the violation for this installation than the lack of adaquate wireway space.
Don
 
LarryFine said:
The space you're using as a wireway is horizontally across the enclosure bottom area, so you'd measure from the bottom of the enclosure to the bottom of the 'guts' multiplied by the depth of that space, from the enclosure cover to the rear surface.

In other words, as if you had X-ray vision, look at the enclosure from one side, not the front. The height is from guts to bottom, and the width is from cover to rear of the enclosure. The 'length' of that space is the enclosure width, not of concern here.
Click to expand...

Now THAT way of looking at it makes sense to me!:smile:

Thanks to all.


314.28(A)(2) :mad:
"minimum dimensions of pull and junction boxes or conduit bodies"

Is a disconnect considered a pull and/or junction box or a conduit body?
 
Dave,
Take a look at the scope of Article 314.
314.1 Scope
This article covers the installation and use of all boxes and conduit bodies used as outlet, device, junction, or pull boxes, depending on their use, and handhole enclosures. ...
Click to expand...
You are using the disconnect enclosure as a pull box.
Don
 
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