360 degree maximum

[Isaiah]

Construction is routing 6, 1/C control cables #14AWG in a FOUR inch PVC underground conduit - they have approximately 500 degrees of bends - there is no way they’ll damage the cable with such a small conduit full

Im not the AHJ but it seems this should be allowed - opinions?


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[Hv&Lv]

Asking for permission??
Code says 360, plain and simple.
BUT, as I’ve said in an earlier post:


The 360 degree rule is a bad metric for doing away with sidewall and pulling tension calculations.
There are many cases where an electrician can set up an NEC legal pull and damage the cable.
There are also cases where the same electrician can set up a pull with 720 degrees of bends and not damage or struggle pulling this wire in.

Engineering supervision should take over in certain cases.
The NESC spells it out better…
341.A.2 Pulling tensions and sidewall pressures on the supply cable should be limited to avoid damage. Note; Manufacturers' recommendations may be used as a guide.

 

[roger]

I would do it and not give it a second thought

 

[winnie]

The conduit fill makes little difference; the issue is what is known as the capstan equation.

Basically the tension on the wire scales exponentially with the total angle of bend.

With real world friction reducing techniques, it is likely that the pull could be done without damage. But this is not a certainty, and clearly a code violation.

Jon

 

[xformer]

90.4

 

[infinity]

I would allow it because there is little chance that the extra 140° of bend will make any difference in pulling the cable.

 

[jap]

My question would be how would one know there was 500 degrees of bends unless the broken rule was witnessed before it was covered up?

JAP>

 

[Isaiah]

My question would be how would one know there was 500 degrees of bends unless the broken rule was witnessed before it was covered up?

JAP>

Inspector’s review of duct bank prior to pull


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[LarryFine]

Inspector’s review of duct bank prior to pull

Then you should already know.

 

[acin]

Pull box at 360 degree point?

 

[Isaiah]

Pull box at 360 degree point?

Yes I’ve advised them to add a pull box at the 270 point. Personally I think it’s ridiculous but that’s one of the pitfalls with NEC


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[jap]

Yes I’ve advised them to add a pull box at the 270 point. Personally I think it’s ridiculous but that’s one of the pitfalls with NEC


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If there's an inspectors review of a duct bank prior to pull,, and the inspector didn't flag the 500 degree of bends,,,, and you don't agree with NEC requirements of the 360 degree bend rule, and, you're not the AHJ... why would you be advising on the install of a pull box at the 270d point?

 

[SSDriver]

This code is not perfect but I'm glad it's there when I'm coming to do repairs. I would rather count degree of bends than fight with an Inspector over calculations on pulling tension or have to prove pulling tension with a gage.

 

[EC Dan]

What is the reason for the excessively large conduit? If it's for future capacity, then you would be severely handicapping the future guy who wants to pull another dozen cables through there if you don't put the pull box in.

 

[jap]

What is the reason for the excessively large conduit? If it's for future capacity, then you would be severely handicapping the future guy who wants to pull another dozen cables through there if you don't put the pull box in.

This is the voice of experience.

That is generally the case.

Most think Installing large conduits for future use is a win when actually a single small cable installed first will impede every pull after that.

Been there more than once.

JAP>

 

[kwired]

This is the voice of experience.

That is generally the case.

Most think Installing large conduits for future use is a win when actually a single small cable installed first will impede every pull after that.

Been there more than once.

JAP>

Future add in's often end up requiring to pull out existing, even if you end up pulling it back in with the add in's.

 

[jap]

Future add in's often end up requiring to pull out existing, even if you end up pulling it back in with the add in's.

Hence the downfalls of large spare conduits.


JAP>

 

[kwired]

Hence the downfalls of large spare conduits.


JAP>

If say an underground line, it is less destructive to pull old out and new back in than to excavate for an additional line. There is advantages as well as disadvantages to everything.

 

[jap]

If say an underground line, it is less destructive to pull old out and new back in than to excavate for an additional line. There is advantages as well as disadvantages to everything.

The shutdown of existing operations is usually the biggest disadvantage of all.

I'd rather pull in 6 control cables in a 1" conduit to a specific location and leave them alone as to pull in 6 of the same in a 4" conduit only to have to interrupt operations just to pull the existing out to add more in the future.

But that's just me.

JAP>

 

[Isaiah]

If there's an inspectors review of a duct bank prior to pull,, and the inspector didn't flag the 500 degree of bends,,,, and you don't agree with NEC requirements of the 360 degree bend rule, and, you're not the AHJ... why would you be advising on the install of a pull box at the 270d point?

The inspector HAS NOT seen it yet


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