360 degree maximum

[kwired]

Supply house have a master reel that can do that in one length without a splice?

supply end set up at the factory and keep pulling at whatever rate they can produce it at

 

[electrofelon]

supply end set up at the factory and keep pulling at whatever rate they can produce it at

That's sorta what they do for these intercontinental communications cables. Have the ship pull up, run the cable out the factory window and start winding it in the hold

 

[Isaiah]

Not familiar with those products, what are the applicable NEC article numbers?

I assume we were discussing PVC conduit. In which case (2017) 352.26 says "Bends — Number in One Run. There shall not be more than the equivalent of four quarter bends (360 degrees total) between pull points, for example, conduit bodies and boxes."

Seems clear to me if you connect together (15) 10' sticks of PVC conduit, and make 6 degrees of bend at each stick, that's the equivalent of a quarter bend.

Cheers, Wayne

Say you have 200 feet of 2” PVC conduit installed in a 24” deep trench that weaves back and forth like a snake at roughly 5 degrees per section - would you include all those ‘mini-bends’ into the calculation assuming you also have factory 90 stub ups at each end? This scenario occurs frequently in the field. Rarely does a small diameter PVC conduit run straight as an arrow.
I would say “no” - only count the 90’s.


Sent from my iPhone using Tapatalk

 

[paulengr]

Say you have 200 feet of 2” PVC conduit installed in a 24” deep trench that weaves back and forth like a snake at roughly 5 degrees per section - would you include all those ‘mini-bends’ into the calculation assuming you also have factory 90 stub ups at each end? This scenario occurs frequently in the field. Rarely does a small diameter PVC conduit run straight as an arrow.
I would say “no” - only count the 90’s.


Sent from my iPhone using Tapatalk

Look getting deeper into this it’s how much the cable rubs on a bend compared to a straight run. On the straight run we have the weight per foot times the coefficient of friction times the footage plus the weight per foot tines the vertical height as our pull force. Then we use that force times exp(coefficient of friction x bend angle in radians) which is the capstan equation. It’s the exponent that is driving things. So yes those small bends matter but at some point you have to be realistic about what you are estimating. How much is down force from friction and sidewall pressure and how much id an actual bend? I prefer to avoid bad pulls in the first place. A strategically placed LB usually does the trick.

 

[Isaiah]

Look getting deeper into this it’s how much the cable rubs on a bend compared to a straight run. On the straight run we have the weight per foot times the coefficient of friction times the footage plus the weight per foot tines the vertical height as our pull force. Then we use that force times exp(coefficient of friction x bend angle in radians) which is the capstan equation. It’s the exponent that is driving things. So yes those small bends matter but at some point you have to be realistic about what you are estimating. How much is down force from friction and sidewall pressure and how much id an actual bend? I prefer to avoid bad pulls in the first place. A strategically placed LB usually does the trick.

Except you can’t use a LB on U/G PVC


Sent from my iPhone using Tapatalk

 

[roger]

Except you can’t use a LB on U/G PVC


Sent from my iPhone using Tapatalk

 

[wwhitney]

Say you have 200 feet of 2” PVC conduit installed in a 24” deep trench that weaves back and forth like a snake at roughly 5 degrees per section - would you include all those ‘mini-bends’ into the calculation assuming you also have factory 90 stub ups at each end?

I'm not aware of any theory that would let you ignore those bends. If I did the math right, a 10' piece of conduit that ends up with a smooth 5 degree bend along it would have a radius of curvature of 115' or so, and the end would be 5.25" offset from straight. So surely conductors pulled through there would be rubbing on the sidewall.

Now if you got the bend down to 1 degree per 10' stick, that would be a radius of curvature of 573', and the end would be offset only 1". So on a larger conduit like 2", I could see the argument that if the bends are opposing each other as you go, the conductors would end up pulled straight down the middle and not actually rub on the sidewall. I don't really know.

Cheers, Wayne

 

[Isaiah]

I'm not aware of any theory that would let you ignore those bends. If I did the math right, a 10' piece of conduit that ends up with a smooth 5 degree bend along it would have a radius of curvature of 115' or so, and the end would be 5.25" offset from straight. So surely conductors pulled through there would be rubbing on the sidewall.

Now if you got the bend down to 1 degree per 10' stick, that would be a radius of curvature of 573', and the end would be offset only 1". So on a larger conduit like 2", I could see the argument that if the bends are opposing each other as you go, the conductors would end up pulled straight down the middle and not actually rub on the sidewall. I don't really know.

Cheers, Wayne

In the real world 1 degree curvature isn’t going to happen with long straight runs of 2” PVC. More likely 1,2,3,4,5,6 degrees and so forth would occur.
Sidewall pressure would be negligible using generous amounts of lubricant like polywater for example. Also engineering manhours would not normally be allocated for the effort you’ve described.


Sent from my iPhone using Tapatalk

 

[jap]

I have seen some that are picky and some that could care less about how they run cables. Most the latter ones though are more of the IT guy that knows where to plug things in at the equipment and how to set up software but can't fish a cable down a wall to save their *** if needed.

And these are the same guys you're expecting to pull all their cables out of an underground conduit with 500 degrees of bends to install another one yet not create a shutdown of existing operations?

I'd install the pullbox, and, I'd use it also.

I'd feel pretty confident attempting a pull of an additional cable with a 4" conduit and 250d of bends to a pull box in the middle.

Same pull with 500d of bend and no pull box,,, not so much.

JAP>

 

[kwired]

Except you can’t use a LB on U/G PVC


Sent from my iPhone using Tapatalk

Want more confusion with future changes, locates, etc.... I ran into buried T fittings before.

 

[Isaiah]

Want more confusion with future changes, locates, etc.... I ran into buried T fittings before.

Never seen one that before.


Sent from my iPhone using Tapatalk

 

[Hv&Lv]

Want more confusion with future changes, locates, etc.... I ran into buried T fittings before.

Ditto…
A royal PIA
Pipe horn found seven of them in some light wiring on a property

 

[roger]

Use to use Tee's for conduit drains between buildings on school campuses. There were and maybe still are fittings made for the purpose and was nothing but a glorified Tee

 

[kwired]

Use to use Tee's for conduit drains between buildings on school campuses. There were and maybe still are fittings made for the purpose and was nothing but a glorified Tee

did you actually drain it to something or just into surrounding soil?

 

[roger]

did you actually drain it to something or just into surrounding soil?

Gravel and landscape cloth.

 

[kwired]

Gravel and landscape cloth.

I was hoping you put in a tee and then ran a properly sloped drain pipe to some sump or something and then pumped it out when full

 

[roger]

I was hoping you put in a tee and then ran a properly sloped drain pipe to some sump or something and then pumped it out when full

Actually we did run a pipe from one that happened to be on a hill, we took it to a drainage ditch.

 

[jap]

Actually we did run a pipe from one that happened to be on a hill, we took it to a drainage ditch.

That's interesting.

 

[SSDriver]

Any drainage tees I've used that were also spec'd out never need to run anything. They were mostly there to keep water out of the electrical control cabinets. How much water do you expect to see? I know it can be a lot in some instances.

 

[kwired]

Any drainage tees I've used that were also spec'd out never need to run anything. They were mostly there to keep water out of the electrical control cabinets. How much water do you expect to see? I know it can be a lot in some instances.

In humid areas they entire horizontal run can be filled easily just from condensation forming inside. Once you get to point where air flow is impeded condensation probably lessens.

I recall burying a PVC conduit on hot humid summer day one time, then came back to pull conductors the next day. Pull rope was pretty damp when pulled out after just one day. The humid air condenses when it hits the cooler walls of the underground portion of the raceway.