Box Sizing

[Alwayslearningelec]

Have pull box with 28 4" going into to it. Not sure how they will be configured going in.

It's a straight pull. What's the calc? 8x4" then adding all the remaining sizes?

 

[infinity]

If this is for power conductors larger than #6 and a straight pull the minimum size box between the raceway entries is 4*8=32". I would never use a box that small.

 

[Alwayslearningelec]

If this is for power condcutors larger than #6 and a straight pull the minimum size box between the raceway entries is 4*8=32". I would never use a box that small.

But then you need to add the sum of all other conduits, correct?

 

[infinity]

But then you need to add the sum of all other conduits, correct?

Nope.

 

[augie47]

The " + others" is for angle or U pulls (See 314.28)
When sizing, you also need to take into account the spacing you need for locknuts and bushings and not place the conduits too close.

 

[paullmullen]

Source: Illustrated Guide to the National Electrical Code (8th Edition)

 

[Dennis Alwon]

But then you need to add the sum of all other conduits, correct?

The idea is that the number of conduits will make the box significantly larger in width. 28 x 4 = 112 " and that's without extra spacing for locknuts and bushings. I am guessing you would need an extra 3/4" - 1" which would bring the width up to 140" which is almost 12'.

Would it be better to use 2 boxes in this case?

 

[infinity]

The idea is that the number of conduits will make the box significantly larger in width. 28 x 4 = 112 " and that's without extra spacing for locknuts and bushings. I am guessing you would need an extra 3/4" - 1" which would bring the width up to 140" which is almost 12'.

I'm guessing that the conduits are run on a tiered rack so it won't be 28 across.

 

[Choice_Gorilla]

Thats a big box, I’m with Dennis. At least 2 maybe more depending on layout. One box gets punched then someone starts running the pipe out of it while the next box is punched. If someone messes up the layout or forgets some aspect of measuring it’s a cheaper fix. Lastly, maneuvering a 6’ x 12’ can on the ceiling to mount it sounds like a bad time. Don’t know how quick you need it either, might be able to get multiple off the shelf enclosures, rather than a special order. Just my 2 cents.

 

[augie47]

I'm curious...
You have had a number of posts concerning what I assume is the same job and I've gotten lost with the numbers. (40 vs 28, etc_
Can you briefly define what you have as in "X" numbers of feeders (or services) to protected by ??