Number of 90 Degree Bends in a Conduit Run

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dasarmin

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Does the NEC address the maximum number turns in a conduit run. I seem to remember if a conduit run had more than 360 degrees of turns, a pull box or pulling C, LB, etc had to be installed.
Is there a code restriction, that you cannot continuously pull through more than 360 degrees? If I have a conduit run with (5) 90s can I pull straight through? I would have C throughout the run to help with inserting the pulling string and apply pulling lubricant.
 
dasarmin said:
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Is there a code restriction, that you cannot continuously pull through more than 360 degrees? If I have a conduit run with (5) 90s can I pull straight through? I would have C throughout the run to help with inserting the pulling string and apply pulling lubricant.
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That is a common practice and I am not aware of a code rule that says you can't do that. However make sure that your "C" has a large enough opening to count as a pull point. Assuming that the conductors are #4 and larger, the code requires that the opening be 8 times the trade size of the conduit. See 214.28.
 
Dennis Alwon said:
You are correct 360?. Art 358.26 for emt
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are you saying EMT is a conduit Mr. Alwon....lol......He is referencing Conduit and not Tubing.....ok..ok.....just bustin your chops....here are the other references in terms of conduits..

RMC - Section 344.26
FMC- Section 348.26
LFMC - Section 350.26...... oh heck....just look up all the conduit wiring methods and go to .26.....;)
 
K8MHZ said:
How many degrees are we supposed to add for a 3/8" box offset?

:p
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Hopefully you wont have enough bends in your run to have to worry about that too often. :)
If you do, don't call me to help pull the wire if its of any size at all.


JAP>
 
qcroanoke said:
If you mean a box offset I've been told it is 20 degrees.
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jap said:
Hopefully you wont have enough bends in your run to have to worry about that too often. :)
If you do, don't call me to help pull the wire if its of any size at all.


JAP>
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With a box at each end, that's 40 degrees that many often overlook.

So, from a box to the ceiling and down to another box uses up 220 degrees. A single four bend saddle can take up 120 degrees. That only leaves 20 degrees. Adding an offset (60) would not be a tough pull at all, but put's the run over by 40. Not counting the box offsets put's it on the line.

The above is not a rare example, either.
 
K8MHZ said:
With a box at each end, that's 40 degrees that many often overlook.

So, from a box to the ceiling and down to another box uses up 220 degrees. A single four bend saddle can take up 120 degrees. That only leaves 20 degrees. Adding an offset (60) would not be a tough pull at all, but put's the run over by 40. Not counting the box offsets put's it on the line.

The above is not a rare example, either.
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If someone is going to count box offsets then any sags or bends in the conduit that is not run laser straight might as well be included too.
 
ActionDave said:
If someone is going to count box offsets then any sags or bends in the conduit that is not run laser straight might as well be included too.
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You have to count them. A bends a bend no matter how you look at it.

JAP>
 
I've probably blew it more than once on PVC underground installations where the radius of the ditch was large enough that I only had to use an elbow at each end where it came up out of the ground. :)

JAP>
 
K8MHZ said:
How would you figure the degrees to add to a sag or curve with a 100' radius? For example. Hopefully I'm not going off on a tangent with my question.
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I have no idea. All I know is pulling wire through a curve or an offset is not the same as pulling through a straight run.
 
K8MHZ said:
How would you figure the degrees to add to a sag or curve with a 100' radius? For example. Hopefully I'm not going off on a tangent with my question.
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Pretty simple geometry.
Since the circumference of a full circle (360 degrees) is 2 pi times the radius, you can just measure the fraction of a full circle by dividing the run along the conduit by the radius of curvature times 2 pi.
Example: 10 foot run with a 100 foot radius of curvature would be 10 / (200 pi) times 360. Or roughly .0159 times 360, = ~5.7 degrees.
For a series of sags with supports in between, break it up into upward facing and downward facing segments and estimate the radius of curvature of each one.
 
GoldDigger said:
Pretty simple geometry.
Since the circumference of a full circle (360 degrees) is 2 pi times the radius, you can just measure the fraction of a full circle by dividing the run along the conduit by the radius of curvature times 2 pi.
Example: 10 foot run with a 100 foot radius of curvature would be 10 / (200 pi) times 360. Or roughly .0159 times 360, = ~5.7 degrees.
For a series of sags with supports in between, break it up into upward facing and downward facing segments and estimate the radius of curvature of each one.
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That's what I do.
 
K8MHZ said:
How would you figure the degrees to add to a sag or curve with a 100' radius? For example. Hopefully I'm not going off on a tangent with my question.
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I think if you have a conduit that will sag so much that it would affect your ability to pull wire thru it, you probably would want to rethink your conduit support layout, type specification, or both.
 
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