How to get untangled runs of wire through a pull box?

mgookin

Senior Member
Location
Fort Myers, FL
Agreed. In fact, I'd say it would be virtually impossible to fix them without pulling them out of at least one side and starting over.

Coincidentally, we have to completely start over with at least four of the five runs: the installer damaged the insulation on many of those feeders. One whole conduit shorted out -- one set of (8) 500 MCM aluminum wires blew apart -- and three of the remaining four conduits contain one or more damaged conductors based on a megger test and visual inspection. Even the one "good" set may not actually be good because the section of conduit between the pull box and the MSG is dry, so the megger may not have registered a fault. We still need to perform a wet test on that section of conduit.

We've already removed the aluminum feeders that catastrophically failed (they were the ones marked with red tape in the earlier photo). All these feeders have been in service for 18 months. Here are some photos for your viewing pleasure. :roll:







Interesting photos. Are you sure that damage is not happening during the pull caused by damaged pipe? It would be painful to pull it all again and have the same thing happen.
 

Jon456

Senior Member
Location
Colorado
Avoid using twisted rope if you may be thinking about it. You only want to use double braided poly. This is a big safety feature as triplex twisted rope will not only tend to untwist as stress is imposed on it, hence the wires take up this torque and get twisted, but double braid poly has a very low stretch so if the rope or head fails, you will not have a whip-back that could seriously injure anyone in the line of fire. Even still, the swivel is something I would always use. Set up the reels and maintain even pulling stress on the reels by lubricating the axles and having enough manpower to control the feed. Some beefy tie wraps makes for a nice finish if you get them even enough.
Double-braided poly rope was used by the installation contractor for these pulls, but no swivel was attached. The installation contractor tied mule tape directly to the head of the bundle of wires (eight 500 MCM + one 1/0 AL-XHHW) with a series of half-hitches over a span of about 24-30" from the end of the wire bundle, taped over this head with duct tape, and then tied the braided poly pull line to the mule tape. The cinched mule tape squeezed and stretched the wire insulation at the head. Here is a photo of a section of the feeder inside our distribution panel showing damage to the insulation where the mule tape was tied around the wire:

 

Ragin Cajun

Senior Member
Location
Upstate S.C.
I always thought that was what "should" be done as the first few feet where the pull rope is connected get buggered up. Looks like the previous crew were too cheap to pull out the extra cable.

Where in the conduit did the fault(s) occur?

Be sure to verify that the inside of the faulted conduits were not damaged. I would be surprised if the conduits were not damaged, judging by the damage to the cables. It only takes a little melted conductor sticking to the inside of the conduit to screw things up!

RC
 

Jon456

Senior Member
Location
Colorado
Looks like it would have been wiser to pull some extra length of wire which could be cut off....
He was re-pulling existing wire that was already cut to length. There was no extra wire available to cut off.

IMO, he should have used either mesh cable grips or cable pulling eyes.
 

Jon456

Senior Member
Location
Colorado
Interesting photos. Are you sure that damage is not happening during the pull caused by damaged pipe? It would be painful to pull it all again and have the same thing happen.
The intent of this thread was to learn how to pull large conductors in two directions from a midpoint pull-box, without creating a bird's nest of wires. But since you inquired about the cause of the damage, I'll give you the back story.

The five parallel sets of conduit were 15 years old and four of them contained the (16) 500 MCM aluminum feeders which powered our facility. The installation contractor removed these existing wires from the four conduits and re-pulled them into two of the conduits so that he would have three open conduits through which to pull (18) new 350 MCM copper solar feeders. This is what the in-ground pull-box looked like when it was first unearthed and opened after 15 years:

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And this is what it looked like after the soil was removed from the box (by hand using a plastic scoop, so as not to damage the wires):

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The concrete lower section of this box was formed-in-place, with a solid concrete floor. Over the years, dirt and rocks had washed into the box through gaps between the square corners of the formed-concrete part of the box, and the rounded-corners of the extension ring atop it. The soil had completely buried the wire and conduit openings. The conduits to the distribution panel slope down at an angle away from the box, as pictured in this diagram:



A rational person would presume that at least some debris had washed down into those conduits over the years. In fact, in the 4th photo above you can even see dirt inside the conduit. Nevertheless, the installation contractor did not proof the conduits (despite promising to acquire a mandrel to do so), did not brush or swab the conduits to clean them out, did not visually inspect the conduits (not required, but if I were doing the install, I would have done so to CMA), and did not lubricate the conduits prior to the pull.

I observed the pulls that were performed 18 months ago and I objected to -- and documented -- the pulling methods employed, but my concerns were not addressed. In fact, I concluded at the time that these conductors were very likely damaged during the installation and predicted their probable failure. However, I did not anticipate the extent of the total damage: out of nine runs of conduit in this job, six contained failed feeders. So the damage was not just limited to the re-used aluminum feeders, but a number of brand-new copper feeders were damaged as well. Specifically, the damage comprises eleven out of sixteen damaged 500 MCM AL-XHHW feeders (two out of two conduits; 3,960 ft of wire), three out of eighteen damaged 350 MCM CU-XHHW feeders (two out of three conduits; 2,100 ft of wire), and two out of twelve 500 MCM CU-XHHW feeders (two out of four conduits; 1,120 ft of wire).

So, back to the present day and your question...

After we removed the shorted aluminum feeders pictured above, we pulled a rubber disc mandrel through the conduits and pulled out 6 or 8 angular rocks that were inside the conduit, each about 1" in size. After swabbing, we ran an inspection camera through that conduit and there was no visible damage to the PVC, not even from the violent arcing that occurred at the time of the short (the water inside the conduit probably helped there). Other conduits with damaged conductors will be swabbed and inspected after the existing wires are removed.

Actually, I'm very surprised that the PVC conduit wasn't ruptured by the shock wave of the "explosion" that occurred when the conductors shorted. The short was located near midspan in the 200' conduit run, and water had been ejected from the conduit into the distribution panel with such force, that the entire utility room that houses the distribution panel was wet -- with water dripping off the ceiling and walls -- even though the distribution panel was completely closed with only some small louvered vents at the bottom and top of the front panel.
 

Jon456

Senior Member
Location
Colorado
Has anything been done to seal the corners of the formed in place box where it meets the extension ring?
After the new wiring work was completed 18 months ago, I had cement mortar packed around the bottom of the lowest extension ring where it seats on the formed-in-place box to prevent further ingress of soil. I also sealed the joints between each of the extension rings (four total + a top ring) with Conseal. When we recently re-opened the box, there was no soil in the bottom of the box.

Of course we had to break off the mortar in order to remove the rings so that we could pull out the damaged conductors and pull in new ones.
 

ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
The intent of this thread was to learn how to pull large conductors in two directions from a midpoint pull-box, without creating a bird's nest of wires.
Get back to this in a minute.

But since you inquired about the cause of the damage, I'll give you the back story.

The five parallel sets of conduit were 15 years old and four of them contained the (16) 500 MCM aluminum feeders which powered our facility. The installation contractor removed these existing wires from the four conduits and re-pulled them into two of the conduits.....
Well dropping that info in is like switching from old black and white television to HD colour with surround sound..

Let's revisit the question in the first paragraph- to get nice wires in the cristy box you have a good crew, new wires, and you take your time. If it is the kind of work you do then it is what you do. There is no book on how to do it.

Now to un-pull and then re-pull 500MCM out of a ground box and pull it back in and make it look like it did the first time... there's no way unless they are only about 45' long. That's my opinion. I have never had to do it. I can only imagine what it would be like.

But that is not the problem anyway. The problem is the crap in the pipe. And yes, anybody with any active brain cells remaining in his head would have made sure none of that was in there.

Oh, and one more thing...You don't hire some bottom feeding hack that tells you he can do it for less than those rip off guys.
 
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Jon456

Senior Member
Location
Colorado
Well dropping that info in is like switching from old black and white television to HD colour with surround sound..
Like any good thriller, it's best to build the suspense until the end of the movie! ;)

Let's revisit the question in the first paragraph- to get nice wires in the cristy box you have a good crew, new wires, and you take your time. If it is the kind of work you do then it is what you do. There is no book on how to do it.
I think the "good crew" and "take your time" are the key points here. New wires will certainly make the job easier, but I bet a good professional crew working methodically could get similar results even with the used wires.

On the other hand, a crew that is not using the proper tools and not applying industry best practices will produce the kind of tangled mess seen in the photo below, and cause damage as seen in my post #16 & #22, even when they are working with new wire.

There are now 34 feeders (and 5 EGC's) running through that pull box: sixteen of them are our original 500 MCM AL-XHHW facility service feeders (which the contractor assured us he could remove and re-pull without problem) and eighteen of them are brand-new 350 MCM CU-XHHW feeders for our new solar installation. As you can see, the pulls using new wire don't look any better than the pulls using the old wire:



In this photo, the conduit ends that are most visible (three on the right and three at the top-left) are the ones containing the brand-new copper solar feeders. The least-visible conduits are the ones containing the old aluminum feeders.

Not only do the new-wire pulls not look any better, but a number of them are also failed due to insulation damage.

But that is not the problem anyway. The problem is the crap in the pipe. And yes, anybody with any active brain cells remaining in his head would have made sure none of that was in there.
The crap in these old conduits was the primary problem here, but not the only one. The crew also damaged the insulation on two other new 500 MCM copper wires, even when pulling into brand-new conduit that they themselves had installed.

Oh, and one more thing...You don't hire some bottom feeding hack that tells you he can do it for less than those rip off guys.
Just to be clear, I was not the one who awarded this contract. In fact, I was not even involved in the planning phase of this project (otherwise, I would have caught a number of errors in the engineered plans); I was brought on at the time construction started.

The contractor is an electrical engineer and licensed electrician. He came well-recommended and his company already had a history of a number of large commercial jobs, including some state government contracts.
 

Jon456

Senior Member
Location
Colorado
If it is the kind of work you do then it is what you do. There is no book on how to do it.
I forgot to reply to this comment. I agree that there is no substitute for good training and on-the-job experience. Nevertheless, there are things that can be learned from books and other resources. Southwire publishes an excellent "Installation & Application Guide for 600V Conductors" that discusses some "industry best practices" for pulling wires. And Mike Holt's forum is a virtual treasure-trove of knowledge and experience.

I posted this thread to try to glean some of the "art of the trade" for neatly pulling in large conductors, and I've already gotten several useful pieces of advice. :thumbsup:
 
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