Bends

A

Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
Seeing many jobs not have notes that they want pulll box every 270 degree and not 360. Guess this makes pulling easier. Any reason from an installation why you would want to put box every 360 and not 270?
 
Depends on we’re bends are and the degree- would rather pull through 4-90 36” sweep then 3-90 12” sweep- plus if the bends are close to each other or spaced—-
There is pulling calculations that’s what you should rely on

That rules is like the NEC trying to fix something that installer knows better
 
Alwayslearningelec said:
Seeing many jobs not have notes that they want pulll box every 270 degree and not 360. Guess this makes pulling easier. Any reason from an installation why you would want to put box every 360 and not 270?
Click to expand...
I always want as few pull points at possible..every pull point adds labor and the additional handling of the conductors at any pull point increases the chance for conductor insulation damage.

Using a pulling calculator, I would even be willing to go beyond 360° if the code would permit that.

Often those calculations will show you can go well beyond 360° without conductor damage either from the pulling tension or the sidewall pressure. Sidewall pressure is the crushing force on the insulation as the conductors are pulled around bends and is a function of the pulling tension and the radius of the bend. In the calculations I have done, the sidewall pressure and not the pulling tension has always been the limiting factor. I have used 3" radius bends on a 2" conduit pull, to avoid additional pull points
 
When pulling wire larger then #2 by hand tried to keep it to 270 degrees. We had an electrician who would run 2 & 3" conduit and always had LB'S facing the wrong direction leading into buss duct switches making it that much harder to pull thru 360 degrees in bends. Some of these LB'S were 20 to 30' off the ground. If the long portion of LB was parallel with the ground made it easier to pull straight down while standing on the ground, Genie or sizzles lift. Found it more difficult at times to pull large wire where there was a 45 degree kick right before or after a 90 especially if there was two of these in one run but still only 270 degrees verses a run with four 90's. Crouse Hinds for one made great LB'S with a roller on one end that did make it easier to pull wire where short portion of LB was parallel bro the ground.
 
Alwayslearningelec said:
Seeing many jobs not have notes that they want pulll box every 270 degree and not 360. Guess this makes pulling easier. Any reason from an installation why you would want to put box every 360 and not 270?
Click to expand...
I was about to say it's probably both a CYA note, and just a standard spec. paragraph nobody thinks about too much.

But another thought is that a 270 degree limit would make it easier to pull the wires out and replace them if a circuit or feeder went bad.

With that said, I'm not sure what the ramifications could be if a feeder went bad, and nobody can get the wire out because there was an extra bend. At the very least, the owner's perception the installing company is probably going to get a little worse.
 
This sounds like another waste of money spec. Reality is that even with a pull box every 3 quarter bends most of the time the installer will pull through them anyway.
 
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