360 and more

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Natfuelbilll

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We all know the 360 Code limit on conduit bends. Jobs I design carefully consider this requirement.

Reviewed some plans that are showing 5 or more 90 degree bends. The pipe is 4" PVC. The bends are RGS. The designer said "the conduit is oversized".

What are your experiences pulling wire in conduit systems with greater than 360 bends?
 
If the bends are very close together (e.g. dogleg offset) the effect may be greater than for widely separated bends.
The location of the bends relative to the direction of pull can have an effect too.
Oversize helps, I am sure, but hard to quantify by how much.
What is being pulled?
 
GoldDigger said:
If the bends are very close together (e.g. dogleg offset) the effect may be greater than for widely separated bends.
The location of the bends relative to the direction of pull can have an effect too.
Oversize helps, I am sure, but hard to quantify by how much.
What is being pulled?
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400kcmil aluminum
 
I don't think NEC allows more than 360 degrees regardless if you have a larger conduit.

However, larger than allowed conduits do help with the wire pulling.
 
Oversized pipe makes no difference, you are restricted by code to 360 degrees unless you put in a box or a condulet.

As far as pulling through more than 360, I've been on pulls with five or six nineties along with kicks and offsets where we pulled straight through a j box or condulet and not had a problem.
 
ActionDave said:
Oversized pipe makes no difference, you are restricted by code to 360 degrees unless you put in a box or a condulet.

As far as pulling through more than 360, I've been on pulls with five or six nineties along with kicks and offsets where we pulled straight through a j box or condulet and not had a problem.
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+1
360 degrees is 360 degrees.
 
Just because it is on the plans does it necessarily materialize in the field?

You may have 5 bends on the plans but the foreman may find an easier way to reduce the number of bends.
 
qcroanoke said:
+1
360 degrees is 360 degrees.
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Some basic physics and reality:

Not totally true, depends on if pulling horizontal, up, or down.

Since pull force = Static force * e-(u*wrap), wrap is in radian, u is coefficient of friction.

If a horizontal pull, then static force is mostly the force needed to unwrap the wire spool plus the force to bend and unbend the wire at each bend.

Hence, pull force varies with wire stiffness and material (coeff of friction with conduit)

Now if the spool is above a vertical run with very flexible wire, one can subtract the first bend,

etc..... one can then easily visualize how a 2nd person pushing on a stiff wire at the conduit entrance subtracts from the static force, etc. etc...
 
You cannot have more than 360* between pull points. The end. Period.

I've been on pulls where comm cable has been pulled 3 90s and stuck.

I have pulled comm wire thu 7 90* bends, and also had it stick/break on 4.

Do not push this code, you WILL regret it. The stuck/broken cable we had was at the 3rd 90 of a 3" 180' conduit with 100pr and numerous cat5e/cat6 (WAY under conduit fill). EC had to disassemble the run to get our wire thru.
 
JFletcher said:
You cannot have more than 360* between pull points. The end. Period.
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Really, what part of that do some people not understand?
And as far as "that's what the print shows" being the excuse. That never worked on me when I was inspecting.
Who do you think was going to hear about it if the customer wanted to know "how did this happen?" I was going to hear about it, if I let it go or if I missed it. I was the one that heard about it.
 
360 is the limit. On occasion will bypass the pull point in the middle and pull through 5 or 6 elbows with large conductors especially if part of the run is vertical and we're feeding down. Don't tell anyone. ;)
 
qcroanoke said:
Really, what part of that do some people not understand?
And as far as "that's what the print shows" being the excuse. That never worked on me when I was inspecting.
Who do you think was going to hear about it if the customer wanted to know "how did this happen?" I was going to hear about it, if I let it go or if I missed it. I was the one that heard about it.
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there is apparently an exception around elevator shafts, or if you are not the one pulling wire thru that raceway, that allows as many quarter bends as it takes (9 is my personal record for seeing). I cant seem to find it in MY NEC, but apparently those clauses are in others. I must have a misprinted version. /sarcasm
 
ActionDave said:
He who hasn't can cast the first stone.
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I haven't. Call me a wire jockey virgin, I dont care. The aforementioned comm run that stuck at the 3rd 90, two BIG guys tried to yank it thru, they wound up ripping the all-thread from the strut/ceiling. After that, we unfurled 180' of Clear-Glided-to-heck cable back out, and the EC who ran our 3" EMT wound up removing the 3rd 90, pulling our wire into the floor, back up and in, and reassembling the conduit. Not code, but at that point no one cared.

He vac'd a string thru the same conduit effortlessly...
 
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