Limit on 90's

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Yes, the total degrees of all bends between junction boxes or conduit bodies can not exceed 360 degrees. This should be in each applicable wiring method article such as xxx.26. For example EMT is 358.26.

Chris
 
In one conduit run you can have as many 90's as you want as long as there are pulling points so that no section of the run contains more than 360 degrees.
 
Mr. Valdez,
You don't always have to use a conduit body or condulet. Often you can get by with using an ordinary box which is much [75%] cheaper.
But the main thing to realize is that you will eventually have to pull wires through it and, the fewer the bends, the easier the pull. If you put some thought into it, you should be able to make the entire run with three 90? bends. And, if you can, make them super radius bends.
~Peter
 
peter said:
Mr. Valdez,
You don't always have to use a conduit body or condulet. Often you can get by with using an ordinary box which is much [75%] cheaper.
But the main thing to realize is that you will eventually have to pull wires through it and, the fewer the bends, the easier the pull. If you put some thought into it, you should be able to make the entire run with three 90? bends. And, if you can, make them super radius bends.
~Peter
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Just how do you arive at only 3 90's ?
 
Jim W in Tampa said:
Just how do you arive at only 3 90's ?
Click to expand...


Only 3-90's? I wish that were always true. It would put the pullbox and condulet guys out of business.;)
 
I have a 700 foot ground conduit to run. It goes thru a dozen rooms and change s elevation about ten times. You can't get every run done with 4 or less 90s, or 360 degrees. It just isn't always possible with out a unilet or a box.
 
360 is the MAX however you get to that, make sure to take in account box offsets and such.

Trust me If the max was anything over 360 you wouldnt want to go over it anyways.

3 #12s in a 3/4 conduit can be a royal pain in the ass to pull in in anything 360 deg +.
 
georgeswe said:
360 is the MAX however you get to that, make sure to take in account box offsets and such.

Trust me If the max was anything over 360 you wouldnt want to go over it anyways.

3 #12s in a 3/4 conduit can be a royal pain in the ass to pull in in anything 360 deg +.
Click to expand...


For large conduits with large conductors we typically pull through more than 360 degrees worth of bends at one time. It wouldn't be uncommon to pull through a 3.5" conduit run with 6 or 7-90's in one shot with 4-500kcmil conductors and a pulling machine. The code requires pullboxes every 360 degrees, it's up to you whether or not you'll need to use them.
 
Trevor,
When you do that, do you calculate the sidewall pressure to make sure that the insulation is not being damaged by the crushing force that is created when pulling around the 90s?
 
I guess to answer your original question, as has already been stated, a MAXIMUM of 4 90's can be installed in a conduit run from pull point to pull point which can be a box of fitting such as an LB. However be mindful of every single bend in the pipe you have in the entire run. Box bends can sometimes be overlooked as well as kicks. If the run has a hefty combination of both of these, the number of 90's may come down to 2 or even 1 for that matter. Make life easier for yourself and toss in a box whereever it is practical to satisfy the requirement and make your pull a lot easier.
 
3- 90s . amiture 2- 90s one out of the box aimming at your final destination, straight through the space in between ( who cares if its 4' off the floor in a doorway) and one 90 down to the box. Done. If your really good you could use two 45's. Carry on gentlemen.
 
For the minimun of three bends, allow one length vertical [z axis], one west [x axis] and one north [y axis]. And then perhaps another vertical drop to your destination box. Hence, three bends.
According to geometry, a straight line is the shortest distance between two points, so you should have no bends at all. But people would be tripping over it or ducking under it -- like Caution Tape -- and the boxes might have to be mounted at peculiar angles?!
Now two bends would also be possible. Vertical to floor, DIAGONAL across room and then vertcal to destination.

Celtic,
I've thought about this matter of large bending radius being easier to push. It would seem intuitive that a large, gradual bend would be easier to do. Just as you can take a curve faster on a freeway on ramp rather than the sharp, 90? corner at 2nd and B Street. In fact, carrying this reductio ad absudum to an extreme, you cannot pull at all through a plumbers 90? elbow.
To some extent, the flexibility of the cable or wire itself should have some affect. Is it not harder to bend 350 sq. mils to a 6" radius than a 24" radius?
But some mathematical geeks have contrived their sophisticaticated formulas which usually include some undefined element, a value that is in some book you don't have [shades of Groucho in "A Day at the Races"] and, of course, a Konstant which is whatever it takes to make the results conform to reality.
And they are right. The total force is the same for the entire pull [except for my quibbles]. But in the field, one man can only push so hard or pull so hard. I liken it to pushing a wheel barrow with a 100 kilogram gold brick in it up this 200' hill. Now the total amount of work done, any way you look at it, is going to be 44,000 foot pounds. However one side of the hill has a 45? slope and the other side has a 5? slope. I wager that your preference would be to push it up the shallower slope.
~Peter
 
peter said:
Mr. Valdez,
You don't always have to use a conduit body or condulet. Often you can get by with using an ordinary box which is much [75%] cheaper.
But the main thing to realize is that you will eventually have to pull wires through it and, the fewer the bends, the easier the pull. If you put some thought into it, you should be able to make the entire run with three 90? bends. And, if you can, make them super radius bends.
~Peter
Click to expand...


I tried the super radius bend method before and got burned.Scenario was scissor trusses from the 2nd floor and as the jurisdiction required conduit for a pool panel.So I made soft sweeping arches through the trusses.From point A to point B.Inspector cited more than 360 degrees of bends.Live and learn.
 
don_resqcapt19 said:
Trevor,
When you do that, do you calculate the sidewall pressure to make sure that the insulation is not being damaged by the crushing force that is created when pulling around the 90s?
Click to expand...


Actually no. Each run is evaluated in the field based on length of run, conduit fill, etc. The run I mentioned had a vertical section of about 70' feet with a few of the 90's. In that section of the run, the weight of the conductors made them literally feed themselves.
 
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