360 degree maximum

[Isaiah]

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.

NO FUTURE Cables


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[Isaiah]

?

 

[winnie]

Umm. You've gotten reasonable answers. The installation as described is an explicit code violation, which will nonetheless probably work just fine.

Any further discussion might best be directed towards how the code could reasonably be changed, what you can recommend to ensure a safe installation even with the known code violation, or how to convince the entities involved to do a legal installation.

IMHO the best approach is to add the pull point so that these conduit could be used in the future for other needs. Even though this is not expected at the present time.

Jon

 

[Dale001289]

Umm. You've gotten reasonable answers. The installation as described is an explicit code violation, which will nonetheless probably work just fine.

Any further discussion might best be directed towards how the code could reasonably be changed, what you can recommend to ensure a safe installation even with the known code violation, or how to convince the entities involved to do a legal installation.

IMHO the best approach is to add the pull point so that these conduit could be used in the future for other needs. Even though this is not expected at the present time.

Jon

I agree with Roger.
Any reasonable inspector, engineer or electrician can see this is a simple, safe pull, especially since the OP has stated there will be no future cables.


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[infinity]

Even if you installed a pull point it's highly likely that no one will use it when pulling in the cables.

 

[ActionDave]

Even if you installed a pull point it's highly likely that no one will use it when pulling in the cables.

About 99.9% likely. I've never done anything other than pull straight through a Cee condulet, almost never pulled out and back into boxes unless there is a change in direction of the conduits. For branch circuits with stranded wire and a short run I've been known to pull through an LB.

 

[kwired]

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>

How easily it can be shut down factors in. If something that runs nearly all the time shut down is maybe a bigger deal than with something that normally is shut down on a regular basis

 

[paulengr]

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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The wiring rubbing on the corners is what causes bend limitations. Straights hardly matter.

Using your numbers I did 100 feet three legs with 90 in each then four legs of 50 feet with 90s in each for 500 feet with about 560 degrees of bends. I come up with about 150 pounds force needed. Keep in mind it’s still not Code and won’t pass inspection even if it is physically possible. Obviously snags aren’t likely. A single C conduit body makes you legal even if you never use it. Make it a tee with a lamp post and you are golden. Plus you can reduce the conduit since way down to say 1 inch and save a boatload of money or run a 6 conductor direct burial cable and plow it in.

 

[Isaiah]

The wiring rubbing on the corners is what causes bend limitations. Straights hardly matter.

Using your numbers I did 100 feet three legs with 90 in each then four legs of 50 feet with 90s in each for 500 feet with about 560 degrees of bends. I come up with about 150 pounds force needed. Keep in mind it’s still not Code and won’t pass inspection even if it is physically possible. Obviously snags aren’t likely. A single C conduit body makes you legal even if you never use it. Make it a tee with a lamp post and you are golden. Plus you can reduce the conduit since way down to say 1 inch and save a boatload of money or run a 6 conductor direct burial cable and plow it in.

Fine except everything is underground PVC so can’t use a C condulet. Question is also whether the inspector will count a very large 90 degree bend (48”) as a sweep instead of an actual bend which is usually a factor radius bend


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[winnie]

The inspector should count sweeps the same as bends because they have similar effects on pulling tension.

Sweeps reduce sidewall pressure not tension.

Jon

 

[tortuga]

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

I had to google that, interesting read:

https://en.wikipedia.org/wiki/Capstan_equation

I have found when running conduit for low voltage / control wires / data / fiber the IT people are waaaay waaay more picky about the number of bends and size of conduit, than we are for standard XHHW McM wire.
The IT crowd usually require a section of conduit be no longer than 100ft or contain more than two 90 degree bends between pull points or pull boxes. And they usually dont want more than 3 cables in any conduit.
Thats not enforceable of course other than in the contract specs and getting paid.

 

[Isaiah]

The inspector should count sweeps the same as bends because they have similar effects on pulling tension.

Sweeps reduce sidewall pressure not tension.

Jon

I’d have to disagree with your take on ‘similar effects’ on sidewalk pressure if you mean they’re essentially the same. A factory 90 degree elbow is far less friendly than a 90 sweep.


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[gene6]

I bet a quick look over any bid documents would prevent such a install.
If your not the AHJ Isaiah what is your role in this?

 

[ActionDave]

I’d have to disagree with your take on ‘similar effects’ on sidewalk pressure if you mean they’re essentially the same. A factory 90 degree elbow is far less friendly than a 90 sweep.


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I agree with that. The guys with the slide rules in their pocket and pulling calculators disagree. I can tell the difference between them when pulling by hand.

 

[tortuga]

Paul just did some calcs in post #28

Straights hardly matteUsing your numbers I did 100 feet three legs with 90 in each then four legs of 50 feet with 90s in each for 500 feet with about 560 degrees of bends. I come up with about 150 pounds force needed.

Interesting I have never done a pull tension calc before but for

6, 1/C control cables #14AWG

a quick google says .008 lbs per kcmil
So if its 14 THHN control wire thats 4100 kcmil X .008 = ~33lbs

Other common sizes would be:

AWG​	kcmil​	lbs pulling tension​
12​	6530​	52.24​
10​	10380​	83.04​
8​	16510​	132.08​
6​	26240​	209.92​

 

[paulengr]

I’d have to disagree with your take on ‘similar effects’ on sidewalk pressure if you mean they’re essentially the same. A factory 90 degree elbow is far less friendly than a 90 sweep.


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I tend to agree. In practice there are no edges in a bend vs an elbow. Each joint adds some friction.

 

[paulengr]

Here is the thing. I work for a large motor shop. We often get involved in XXL projects like 5000 HP compressors, 800 HP 460 V motors, plus switchgear and drives for this stuff. We have been burned repeatedly due to lack of wire bending space, bad pulls (even ones that did not exceed 360 degrees), and conduit sizing issues. Sure you can get a 20k puller and rope. You can make a lot of spaghetti that way and may pull wire apart in a conduit making it permanently unusable. But you can adjust things to where you can do reasonable pulls that don’t destroy wire or injure anyone. Because all it does is blow up the costs and the schedule.

So yes, we run pull calculations. What we find is that it works and saves time and money.

 

[roger]

If your not the AHJ Isaiah what is your role in this?

Click on the members name and it will take you to their profile.

FWIW, it really doesn't matter in this instance, it could be curiosity.

Roger

 

[ActionDave]

Here is the thing. I work for a large motor shop. We often get involved in XXL projects like 5000 HP compressors, 800 HP 460 V motors, plus switchgear and drives for this stuff. We have been burned repeatedly due to lack of wire bending space, bad pulls (even ones that did not exceed 360 degrees), and conduit sizing issues. Sure you can get a 20k puller and rope. You can make a lot of spaghetti that way and may pull wire apart in a conduit making it permanently unusable. But you can adjust things to where you can do reasonable pulls that don’t destroy wire or injure anyone. Because all it does is blow up the costs and the schedule.
So yes, we run pull calculations. What we find is that it works and saves time and money.

And this relates to pulling 14 AWG conductors in a four inch conduit? Did you ever do that calculation?

 

[tortuga]

And this relates to pulling 14 AWG conductors in a four inch conduit? Did you ever do that calculation?

He did it in post #28