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We’re getting ready to pull 4/0 cable from our home to our shop. We already have 3″ conduit in place. Since this is our first attempt at pulling heavy underground cable, our main concern is how to secure the cable to the pull rope. We have read about “Socks”, but the cost seemed prohibative for a one time job. Any help would be greatly appreciated.
Thanks
Dave Skillman
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Replies
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Dave,
How many cables are you pulling in? There are a number of ways to do this, but an easy one is to securely tape a nylon rope to one of the cables then individually tape on the remaining cables, staggering them so you don't end up with a big knot of tape on the end. Use pulling lubricant and it should go well.
Tape a foam "mouse" to the end of your rope and pull it through your conduit with a shop-vac. This will get the rope fed through to the end you're going to pull from.
Eric
*Thanks Eric!We're pulling a 3 cable set - standard entrance cable. The nylon rope was already fed through the conduit, during installation of the conduit. We were able to figure out that part. The foam mouse does ease our concern of how the re-feed the rope if the cable comes loose in mid pull.I'm on my way to the store for cable lub!Thanks again!Dave
*Use the mouse one more time- to clear the pipe of any dirt that may have entered the pipe during construction.Since you don't want to buy a 'sock,' you'll want to do it the old fashioned way: Strip a serious amount of cable- say, about three feet worth. About halfway down each stripped portion, separate out about half the strands and twist them to about half the strands of the next cable. When done, tape everything securely. The 'head' you've made should be long, smooth, and fairly flexible. The very end will be looped back and twisted to itself, after passing it through your pulling 'eye.' I try to avoid using pulling lube, but- if the pull doesn't go well, you might have to use it. If you do, apply it to the cable as it enters the pipe- a rag works well.Try to rig some sort of pulley directly above your pipe. This way, you will pull straight and be able to use your weight. Don't be clever and try to say, use your truck's trailer hitch. Too often, you end up having a burr strip your wire's insulation. Just as important, the wires should be laid out straight before the entrance to the pipe. You should have a helper to feed and guide the wire into the pipe. I also suggest including a piece of twine with the pull. This will make it easier to pull other wires later.
*Good suggestions. I suggest pulling another nylon rope (1/4" or 3/8") rather than twine because any future pulling will be harder for having some 4/0 in there already. If you worry about the rope coming off, don't cut it. Let 100' get dragged along with the wire. If it does come off, you'll still have continuous rope through the conduit. And a future pull rope if you are successful.Difficulty is somewhat a function of length, diameter (3" is good), and mostly a function of bends. Only 5 bends are allowed by code, but that is almost impossible to pull through. Three 90-degree bends is usually doable and less than three is easy. When they were building the refineries in my neighborhood, they were always running out of the official wire-pull lubricate. They'd then buy out all the stores of Ivory flakes and use that with some water.Almostly certainly, you used plastic conduit if in 3". That's good, because the joints are much less likely to strip off insulation than poorly installed metallic conduit. You really have to ream that stuff out to eliminate the sharp edge. Again, it is a function of the number of bends. The more bends, the more pulling force. The more pulling force, the greater the risk of stripping off the insulation. -David
*It seems to be standard practice with most wire pulls that I have participated in or have seen to cut off about 3' or more of the wire where it has had the pull rope attached. I understand throwing away the wire where the insulation is damaged from attaching rope, but I often wonder if it is really necessary to throw away several additional feet of wire when the wire and insulation looks intact.
*I have always installed the wire as I assembled the sections of conduit.near the stream never having the nightmare of pulling entrance wire through five nineties, thank you,aj
*i Only 5 bends are allowed by codeNo offense David, but I believe under the NEC that it's a total of 360 degrees between pull points, which could be less than 5 bends (4 x 90 = 360).Jeff
*Jeff: No offense taken. I believe it was 5 bends 12 years ago, when I was last doing much wiring in conduit. (Romex for me now). If I was mistaken or they've changed the code, good. Even with lubricate, a helper, and stout pull rope, 4 bends was my limit. And even then, I'd sometimes add a pull-box to the run. -David
*How far are you pulling this? Friction increases as the pull distance, the amount of bend in the cables, and the number of cables.
*Right, and to add to what George said, choose your direction of pull to feed from the end nearest the most bends. Have a helper push the wire in from the feed end.-- J.S.
*I want to thank you all for the advice. This is a fine forum ferquented by generous folks. FYI - We are pulling approximately 65 ft. of cable through three bends (90,30,90). All bends are full size sweeps.Thanks again!
*> I have always installed the wire as I assembled the sections of conduit. FYI, this is specifically not allowed by the NEC; see article 300-18(a), "Raceways, other than busways or exposed raceways having hinged or removable covers, shall be installed complete between outlet, junction, or splicing points prior to the installation of conductors". The definition of "raceway" includes conduit.That's not to say you can't install pull ropes as the pieces are assembled. That black and orange "truck rope" works pretty well.Using 3" conduit was a good idea. Code allows 2" for 4/0 SE cable, but it's a difficult pull and my local utility doesn't like it. This size cable slides pretty easily through 3" conduit. The elper at the feed end helps alot.
*BarryO:That is a very interesting piece of NEC. So how would the inspector know if you slid the conduit over the wire instead of the wire through the conduit when the job was finished? I wonder what saftey hazzard the NEC is trying to avoid happening? Maybe the ability to feed wire through more than 4 ninties in one run? You have my mind working now!Frank DuVal
*Frank,I think the NEC is trying to prevent bundles of wires being slid through KO's. I see this type of damage a lot when machines are moved.It makes for some nice mysteries to solve when the damaged part is pulled back into the conduit.I would think it would be hard for this type of damage to occur with large feeder conductors like AJ was talking about.Allan
*I also wonder about the damage caused by PVC solvent and glue to the conductors insulation. Tetrahydrafuran is pretty nasty stuff.And maybe, if you can't get it in by pulling in one shot, then you won't be get it out or service it? -David
*I think David has it right. The NEC writers want to be sure that the pull is *possible* so that the conductors can be replaced if necessary. BTW, PVC solvent and glue will eat up those synthetic rope materials. If you assemble over a pull line, make it cotton or manilla, and use that to pull in a larger, stronger synthetic line if that's what you want to use.-- J.S.
*I guess I broke the code for the last twenty years at least ten times...near the stream,aj
*J.S. - Cotton will rot, nylon is best. Haven't had any problems with cement eating it in the limited things I have done.Jeff
*Jeff --I wouldn't anticipate leaving the cotton in place long enough for it to rot.-- J.S.
*I haven't looked at my copy of the NEC Handbook in a long time, but if I remember David & xJohn have it right. The NFPA rules about conduit fill and allowable bends are designed to reasonably ensure that the wires can be pulled, but the ultimate proof of this is if it's actually done.BTW, the NEC Handbook, also published and updated by the NFPA in conjunction with each edition of the NEC itself, is a great resource for answering the "why" and "how to" questions for the sometimes-arcane sections of the Code.
*I guess by "Socks" you mean Chinese Fingers? Cost is prohibitive? You've never pulled ANY wire through conduit before, have you?We pull any decent size pull with a chinese finger, attached to one wire, then tape all the other wires like the others have said-gradually so that there is no big wad.Get at leat a quart of cable lube for 100' and it wouldn't be a bad idea to stop by the parts store on the way back home and get some GO-JO. The white creamy kind. Of course, the inspectors don't like this.
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We're getting ready to pull 4/0 cable from our home to our shop. We already have 3" conduit in place. Since this is our first attempt at pulling heavy underground cable, our main concern is how to secure the cable to the pull rope. We have read about "Socks", but the cost seemed prohibative for a one time job. Any help would be greatly appreciated.
Thanks
Dave Skillman