Pull Box Required

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Pulling tension and side wall pressure calculations need to be done to determine maximum length of a specific conductor pull so that cable damage does not occur.

The 360 rule is for number of bends and does not determine an acceptable length of run.

i.e. if the run is long enough, simply having 1 x 90 deg bend could cause cable damage on the pull.
 
ummm. some workers have a rule of thumb of ever 100' put a pull box as long there aint no more than 360 degrees in the bends
 
kingpb said:
Pulling tension and side wall pressure calculations need to be done to determine maximum length of a specific conductor pull so that cable damage does not occur.
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kingpb you do understand this is an NEC forum and not an engineering forum?

The questions asked here deserve a straight forward answer based on the NEC.

The NEC answer is there is no distance limitation between pull points.

I find that many of your posts only cloud the answer the people are looking for.

Perhaps you could say 'Good design practice dictates side wall pressure calculations.'

Just my opinion take it for what it's worth. :)
 
cloudymacleod said:
ummm. some workers have a rule of thumb of ever 100' put a pull box as long there aint no more than 360 degrees in the bends
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This has got to be one of the oldest electrical urban legends. And in many cases a box every 100' is a waste of money.
 
77401,
It depends on which planet you are on. On earth, it is something like 29,000 miles in circumference. Once around, it's your 360?. Might be hard to pull, though.
But you said, "20' if your pushing the wire in by hand." In a straight run, I've pushed maybe 180'. It depends on the number of bends and their radius [if you use an Ericksen bender].
~Peter
 
kingpb said:
Pulling tension and side wall pressure calculations need to be done to determine maximum length of a specific conductor pull so that cable damage does not occur.:confused:

The 360 rule is for number of bends and does not determine an acceptable length of run.

i.e. if the run is long enough, simply having 1 x 90 deg bend could cause cable damage on the pull.
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How much side wall pressure is there on a 200' vertical pull?:confused:
 
dlhoule said:
How much side wall pressure is there on a 200' vertical pull?:confused:
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Vertical pulls present a completely different set of rules. Conductors are required to be supported. If you have a 500' straight vertical pipe run and pull in 500 Kcmil conductors you'll need a pull box every 50' to support the conductors.
 
infinity said:
Vertical pulls present a completely different set of rules. Conductors are required to be supported. If you have a 500' straight vertical pipe run and pull in 500 Kcmil conductors you'll need a pull box every 50' to support the conductors.
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Trevor What would be the difference between a 500 ft vertical pull like from vault to vault ,as compared to a 500 ft pull from a sweep into a trans and going into a M.D.P.The only difference is the sweeps ??????????
 
allenwayne said:
Trevor What would be the difference between a 500 ft vertical pull like from vault to vault ,as compared to a 500 ft pull from a sweep into a trans and going into a M.D.P.The only difference is the sweeps ??????????
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The difference is that the vertical one (up and down) is required to be supported and the horizontal one (sideways) is self supporting.
 
iwire said:
The difference is that the vertical one (up and down) is required to be supported and the horizontal one (sideways) is self supporting.
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Thanks Bob, that's exactly what I meant. :D
 
I must have been sleeping when i posted I thought at the time vertical side to side not up and down.Now it makes sence.:)
 
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