Max 360 deg bends

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Geoffrey Lyons

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I had seen in a past post (max ft in conduit run) it was stated no limit on length just a max deg of bends , so after 360 (like 4- 90 s) you have to put in a pull box ? And this would be to prevent damage to conducters during pull? and this includes both in an offset 30 &30 -60 , a saddle 22.5 45 22.5-90. Thanks in advance for replies
 
Geoffrey Lyons said:
I had seen in a past post (max ft in conduit run) it was stated no limit on length just a max deg of bends , so
  • after 360 (like 4- 90 s) you have to put in a pull box ?
Click to expand...
Yes.

Geoffrey Lyons said:
  • And this would be to prevent damage to conducters during pull?
Click to expand...
Yes.
Geoffrey Lyons said:
  • and this includes both in an offset 30 &30 -60 , a saddle 22.5 45 22.5-90.
  • Thanks in advance for replies
Click to expand...
Yes.:smile: Your Welcome.
 
The 360 deg rule is the non-thinking persons method for cable installation, and where small conduits and branch circuits are concerned it works just fine. However, for large conductor circuits, feeders, and duct bank installtions it is advisable, to perform pulling tension calculations to verify acceptable pulling tensions and side wall pressures are not exceeded, and especially on medium voltage cable.
 
Geoffrey Lyons said:
....so after 360 (like 4- 90 s) you have to put in a pull box ?
Click to expand...

...or a condulet body.
207l.jpg
 
Geoffrey Lyons said:
Are these calcs in NEC
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No, the NEC does not have pulling tension calcs and does not directly require that they be performed.

Basically the NEC requires that the conductors not be damaged. It is up to the designer / installer to ensure the conductors are not damaged.
 
The NEC does not cover this, unfortunately. The best resource, IMO, is the major cable manufacturers. Southwire and Okonite have very good information in this regard. check there websites. Engineering programs such as ETAP, and others also have the capability to do it. The formulas are pretty straight forward, I actually used the formulas and made myself a MathCad file to to the calcs.

In your research, you will find that often times, it is sidewall pressure (e.g. going around a bend) that becomes the limiting factor, and therefore which end you pull from can become important. (May work one way, but not the other)
 
Watch out for conduit bodies when the wire size is #4 and larger. In many cases a standard "C" or "LB" is not permitted by the code rules. 314.28(A)(3)
 
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