more than 360 in a conduit run

[rszimm]

OK, so I'm freaking out a bit here. Three years ago when I redid my backyard and put in a pool I put a 2" PVC conduit in from my main electrical panel about 120' to an area of my lot I'd like to eventually build a guest-house. (thinking ahead!) It basically goes underground, winds around a bit and ends up roughly in the middle of where I thought the pad would be.

So now we're getting to the build of the guest house and it occurs to me that I've already got 330 degrees of bends in the route and I'm likely to need another 45 and then a sweep up to my electrical panel. That's 330+45+90=465 degrees! (FWIW, the conduit currently still terminates underground at 330 degrees. I still have to uncover the end and run the extra 90+45).

So I'm freaking out that all my forethought is for not. I put in a full 2" PVC even though I'm only running 125 A just in case.

Am I'm screwed here? Should I buy #1 copper instead of #2/0 Al just to make sure things can run. Will that even work? What should I do?

 

[LarryFine]

Place a pull-box at the present pipe end, whether you use it for the pull or not.

 

[kwired]

If you are going to be rejected by an inspector on this you have a problem. If not might want to use super slick type conductors (SIMpull for example) and even then maybe use additional lubricant. I've seen pulling difficulty for XLPE type insulation in underground PVC go from moderate but doable for hand pulling to needing mechanical pulling method just by having three 90 degree bends instead of two.

 

[rszimm]

Thanks. Couple of followups:

1. Would you guys spring for the #1 CU over the #2/0 Al given the situation. It's an extra $400 for approx 150 feet.
2. The current end is 4' underground. Can a pull box extend that far down?
3. The inspections will be fine. The previous run was inspected and passed.
4. Could I uncover the current end, pull the wires through with a lot of slack, and then assemble the remaining conduit OVER the wires. Might be cumbersome, but we're talking about digging up $10k worth of landscaping if I can't get this wire through.....

 

[GoldDigger]

4. Technically, no. The raceway must be complete before the wire is pulled.

Sent from my XT1585 using Tapatalk

 

[growler]

OK, so I'm freaking out a bit here. Three years ago when I redid my backyard and put in a pool I put a 2" PVC conduit in from my main electrical panel about 120' to an area of my lot I'd like to eventually build a guest-house. (thinking ahead!) It basically goes underground, winds around a bit and ends up roughly in the middle of where I thought the pad would be.

So now we're getting to the build of the guest house and it occurs to me that I've already got 330 degrees of bends in the route and I'm likely to need another 45 and then a sweep up to my electrical panel. That's 330+45+90=465 degrees! (FWIW, the conduit currently still terminates underground at 330 degrees. I still have to uncover the end and run the extra 90+45).

So I'm freaking out that all my forethought is for not. I put in a full 2" PVC even though I'm only running 125 A just in case.

Am I'm screwed here? Should I buy #1 copper instead of #2/0 Al just to make sure things can run. Will that even work? What should I do?

Legally you are only allowed 360 degrees of bend between pull points.

If you are willing the break the rules and live with the shame and guilt of it then you can probably pull the conductors in with little or no problem if you made all your connection up correctly.

A lot of problems with pulling wire is that most people don't know (because of a lack of experience ) how to pull wire. Even how you make up the head on a wire pull can make all the difference between and easy pull and a hard pull.

Make up a good head that won't get caught, use plenty of lubricant, make sure you have someone to feed that's not afraid to push the cable into the conduit and then take it slow and easy.

 

[wwhitney]

The current end is 4' underground. Can a pull box extend that far down?

Can you use your remaining 30 degrees of bend to shallowly start rising to reach a reasonable pull box depth?

The pull box could go anywhere after 105 degrees of bend from the start, so that you have 360 degrees or less between the pull box and the guest house. Is there somewhere else in that portion of the run where it would be easier to add an inline pull box?

Also, not sure if this is something anyone would ever do, but in the portion of the run that is between 195 degrees and 270 degrees of bend from the start, you could dig down to the conduit, cut out a section, add 90s to each end to come to grade, and add a pull box there. Then each side of the pull box is under 360 degrees of bend.

Cheers, Wayne

 

[synchro]

One possibility could be to dig down somewhere in the middle of the run that would have a 465 degree cumulative angle after your 45 and 90 elbows are added in. Then you could cut the conduit, attach a 90 to each side, and then bring two conduit stubs up to an above ground pull box. This would result in 465 + 90 + 90 = 645 degrees that is split between 2 conduit runs. If you're lucky there's a suitable place where each run can be 360 or less. For example 360 and 285, 330 and 315, etc.
This proposal would take a little digging but much less than starting over.

Another thing to make pulling easier is to use two 45's to make a 90, or even better get the larger radius elbows (although they're more costly and harder to get).

 

[synchro]

Wayne beat me to it

 

[winnie]

1) A pull box can be 4 feet down if you can get down there to do the pull. Think 'vault'. Probably not worth it for you but certainly doable.

2) Every bend in a conduit is a pull force multiplier, that is why you are restricted to a certain number of bends. If you can push the cable past a pull point then it won't add friction to the pull. While code does not recognize this as a way to put an extra bend in a run, you should know this as a technique to reduce wire tension on any run you pull. Look up the capstan equation to understand this. https://en.wikipedia.org/wiki/Capstan_equation

-Jon

 

[infinity]

You can bury the pull box if you can comply with the accessibility exception. You need some kind of marker for the future access.

314.29 Boxes, Conduit Bodies, and Handhole Enclo-
sures to Be Accessible. Boxes, conduit bodies, and hand-
hole enclosures shall be installed so that the wiring con-
tained in them can be rendered accessible without removing
any part of the building or structure or, in underground cir-
cuits, without excavating sidewalks, paving, earth, or other
substance that is to be used to establish the finished grade.
Exception: Listed boxes and handhole enclosures shall be
permitted where covered by gravel, light aggregate, or non-
cohesive granulated soil if their location is effectively iden-
tified and accessible for excavation.

 

[kwired]

Instead of tearing up $10k of landscaping, hire a directional boring contractor to install a straighter run, or route it to a place where you can put a pull/junction box if they can't get it straight enough.

 

[Gary11734]

Place a pull-box at the present pipe end, whether you use it for the pull or not.

Ditto. Sometimes the answer is pretty easy...

 

[Jon456]

Would you guys spring for the #1 CU over the #2/0 Al given the situation. It's an extra $400 for approx 150 feet.

I've seen enough corroded aluminum conductors pulled out of buried conduit to always want copper. All it takes is a tiny nick or pinhole in the insulation for wet aluminum wires to start self-destructing. And if the conduit is underground, the wires will be wet.

If you can afford $10K landscaping, I imagine you can afford $400 for the peace-of-mind of having copper.

 

[rszimm]

I've seen enough corroded aluminum conductors pulled out of buried conduit to always want copper. All it takes is a tiny nick or pinhole in the insulation for wet aluminum wires to start self-destructing. And if the conduit is underground, the wires will be wet.

If you can afford $10K landscaping, I imagine you can afford $400 for the peace-of-mind of having copper.

Fantastic! So I think I'm coming to a plan of a pull box that I'll bury and identify where it's buried, and run the #1 Copper because it's easier to bend and less likely to corrode.

 

[Jon456]

Fantastic! So I think I'm coming to a plan of a pull box that I'll bury and identify where it's buried, and run the #1 Copper because it's easier to bend and less likely to corrode.

Just make sure that the pull box is not located under the footprint of the new guest house and will not have some kind of permanent structure over it (like a concrete patio).

I don't know if #1 copper is easier to bend per se. It is smaller than 2/0 aluminum, but it's also stiffer. But the smaller diameter will definitely make it easier to pull through the conduit. Regardless if you're using SIMPUL (or similar jacketed wire), I would still recommend wire pulling lube. It's easiest if you have at least 3 people on the pull: one pulling the wire at the destination, one guiding and feeding the wire at the origin, and one applying lube to the wire as it's feeding into the conduit. You can do it with just two, but it's slower and if the person at the origin gets lube on his hands, he won't be be able to help push the wire in.

 

[rszimm]

Thanks.

I've got some of that 210lb poly line for pulling. I've also got around 200' of some serious mule tape that got used to pull in some 350kcmil on the main service line. I'm thinking the mule tape will be more trouble than it's worth but I'll use it if you think it'll be necessary...

 

[Jon456]

I've got some of that 210lb poly line for pulling. I've also got around 200' of some serious mule tape that got used to pull in some 350kcmil on the main service line. I'm thinking the mule tape will be more trouble than it's worth but I'll use it if you think it'll be necessary...

Do not use poly line for this job. Not only will the pull be more difficult due to increased friction, but the poly will cut a groove in the PVC like a wire saw at each bend. On long pulls, it can cut completely through the wall of the conduit.

Use the mule tape.

 

[kwired]

I've seen enough corroded aluminum conductors pulled out of buried conduit to always want copper. All it takes is a tiny nick or pinhole in the insulation for wet aluminum wires to start self-destructing. And if the conduit is underground, the wires will be wet.

If you can afford $10K landscaping, I imagine you can afford $400 for the peace-of-mind of having copper.

Sounds like people are not careful enough handling the conductors when installing them to me. Should always use XLPE types of insulation for underground aluminum, it is tougher than PVC based insulation which also helps.

Same nick in copper conductor still results in similar fault currents, it just takes much longer for the copper to deteriorate to the point of having an open circuit.

 

[Jon456]

Sounds like people are not careful enough handling the conductors when installing them to me. Should always use XLPE types of insulation for underground aluminum, it is tougher than PVC based insulation which also helps.

Same nick in copper conductor still results in similar fault currents, it just takes much longer for the copper to deteriorate to the point of having an open circuit.

The aluminum wire was XLPE. Yes, you're correct: the installers were clearly not careful. But from my observations over the years, uncareful installers vastly outnumber careful installers.

I understand that the fault currents will still occur with copper and that any fault current is unacceptable. The advantage of copper is that, while it will erode over time if there is a fault current, it will not expand and burst the insulation jacket the way that aluminum does. As aluminum corrodes into aluminum oxide, it swells to considerably larger than its original diameter. I've seen it swell to over 3 times the original wire diameter. This causes the insulation to rupture and split beyond the area of the original damage, which exposes a greater surface area of the conductor to the water, which in turn increases the fault current and accelerates the degradation of the aluminum. In one case, there was damage to two adjacent conductors in close proximity. The aluminum in each conductor expanded until they eventually made contact and BOOM! We had to send an inspection camera in to ensure the PVC conduit was not damaged from the explosion. If it had been, it would have been very costly to run new conduit because that buried raceway went under another building.

I would not want any wire, aluminum or copper, to have damaged insulation. But copper does provide a significant advantage when there is damage to the insulation.