Pull boxes 314.28

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Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
What determines at what size becomes too large for a pull box if you have multiple large conduits entering? I assume that after a certain size it would be very tough to install and if so what is that size 42x30x12 or 48x36x12 etc.?

So if you had 7-8 sets of 4" it would be 2 boxes? I read 314.28 but don't see a maximum size.

Thanks.
 
cadpoint

cadpoint

Senior Member
Location
Durham, NC
First your solving for the minimum.

In a straight pull its, 7 or 8 conduits in on right to 7 or 8 conduits on the left side.

In straight pulls 8 (the multiplier), so U take one pipe size and multiply 4" x 8 = 32".
________________________________________________________________

If it's a right angle application then it's 6 (the multiplier)

(6 X 4") +4 +4 +4 +4 +4 +4 = 48"
You stated 8 conduits so you real answer is 52"

(this is the first length) for one travel direction-distance, or is length away from the conduit, to the opposite side that one is determining.
In this case all the conduits are the same thus one has the other mulitplier for the other direction as well.
______________________________________________________________

If one has various sizes then the multiplier is still
(6 X largerest conduit) + all the other conduits on that one size.

Most supply house sizes are of a depth of 6" minimum, 8" in depth, or deeper when getting over 24" sq.

Or you can custom order any size and as far as I know most commerical work they do check the calulations, and I've seem some very large junction boxes!
 
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jumper

jumper

Senior Member
Location
3 Hr 2 Min from Winged Horses
AFAICT You answered your own question, there is no limit on the size. if you look at 314.28(B) you can see that they could be quite large.

(B) Conductors in Pull or Junction Boxes. In pull boxes
or junction boxes having any dimension over 1.8 m (6 ft),
all conductors shall be cabled or racked up in an approved
manner.
 
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Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
Cad, thanks!! Yes, I am aware of the sizing but was curious as to the max size box that might be installed. I would imagine it becomes too big to install at some point. If you have a bank of conduits that could go into a huge box I am guess it would be split to run inot TWO boxes.

cadpoint said:
First your solving for the minimum.

In a straight pull its, 7 or 8 conduits in on right to 7 or 8 conduits on the left side.

In straight pulls 8 (the multiplier), so U take one pipe size and multiply 4" x 8 = 32".
________________________________________________________________

If it's a right angle application then it's 6 (the multiplier)

(6 X 4") +4 +4 +4 +4 +4 +4 = 48"
You stated 8 conduits so you real answer is 52"

(this is the first length) for one travel direction-distance, or is length away from the conduit, to the opposite side that one is determining.
In this case all the conduits are the same thus one has the other mulitplier for the other direction as well.
______________________________________________________________

If one has various sizes then the multiplier is still
(6 X largerest conduit) + all the other conduits on that one size.

Most supply house sizes are of a depth of 6" minimum, 8" in depth, or deeper when getting over 24" sq.

Or you can custom order any size and as far as I know most commerical work they do check the calulations, and I've seem some very large junction boxes!
Click to expand...
 
chris kennedy

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
Beau, we often have really big pull boxes built by our friends at the local metal fab shop. The only requirement for the box to be 'listed' is in wet location, 314.15.
 
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Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
chris kennedy said:
Beau, we often have really big pull boxes built by our friends at the local metal fab shop. The only requirement for the box to be 'listed' is in wet location, 314.15.
Click to expand...

I am aware of that and deal have dealt with a few for hand holes and other pre fab. But what I a thinking about is you may be able to have a box made to ANY size but at some point the size, I would guess, becomes too big to handle/install so maybe going with two smaller boxes side by side would be the more common practice.


Thanks
 
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