I'm putting up a wind turbine. The turbine will be at the top of a 30' 1-1/2" pipe tower. I have a 30' RV extension cord (10ga/3 conductor) that I'm going to cut the ends off of and use as my down-pipe wiring. The wind turbine itself has a foot or so of 10ga stranded wire hanging down on the inside of the tube from the bottom of the turbine (three wires). They say that this wire can support 55# of downtube wiring (total, on the three wires), which is probably right, but I have my doubts that a crimped connector will hold that weight. The extension cord supposedly weighs 12# at its full 36' length, including the ends I'm going to remove, which are probably a pound of the total. Full weight of the 30' that will be dangling will be about 10#, but it has to be able to deal with twisting forces a bit too.

So, I know about the underwriter's knot, and how to tie that for three conductors. But I won't have any kind of stop in the pipe to hold the weight. The best I can do is tie the two sets of three conductors in a way that the wire is holding the weight, not the connector - like an underwriter's knot does. But what I'm looking for would be some kind of knot that's like an underwriter's on top of another underwriter's. Anyone heard of something like that?

  • 1
    Is there a reason you're using cordage for the down-pipe wiring instead of say UF cable? Dec 9, 2016 at 3:43
  • 3
    Is there a reason you aren't supporting the wire's weight with a strain relief affixed to the supports, rather than expecting the connection to take that strain?
    – keshlam
    Dec 9, 2016 at 5:42
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    Let me say it another way. It would never be recommended to support a long cable drop from its connections. In this case the down travel electrical cable should be supported and strain relieved at several places along its length.
    – Michael Karas
    Dec 9, 2016 at 7:38
  • Also, your turbine is too short to be 7200 watts, why the 10 AWG cable and what voltage is this? There are common but fatal errors made in the area of power transmission from small turbines, you may want to discuss it. Dec 9, 2016 at 13:42
  • Let's do those one at a time. @ThreePhaseEel, Cordage instead of UF - is there a reason I'd use UF instead of an extension cord? The manual says a suitable extension cord is what's usually used. Apr 5, 2017 at 17:35

2 Answers 2


The strain relief being referred to in comments:

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You'll probably need to visit an electrical supply store in your area to pick one up, I've never seen them in a big box store.

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    The top three are for pulling. And yes, you need to shop at a real electrical supply not a big box store. Dec 9, 2016 at 13:36
  • What I'm looking for, and no one seems to have come up with yet, would be a strain relief that internally wedges into the pipe. So, look up 'star fangled nut' as one idea. I've never seen such a thing for a strain relief. I've seen service entrance connectors that use a rubber compression seal, but I've never seen anything that clamps outward on the inside of a pipe, leaves room for a cable to pass through, then seals onto the cable to hold it. Apr 5, 2017 at 18:27

Something like this Cable support wedge

Cable support wedge

NEC 300-19 specifies when to use them, in this case if the cable is under 100' none are needed.

Looking at the manual for the next larger wind turbine, it very specifically says to use standard sleeve wire crimps to connect the wiring coming out of the turbine to the down-tube wiring. These support wedges would clearly be better than that. They're wood. You set your wire into one or more of the openings (anyone have experience with these who can tell us how to size them? The 'wire fill' part isn't clear), and drive the wedge into the tube. The wood compresses going into your pipe/conduit, and compresses onto your cable in the process, holding it in place.

Hope that helps someone in the future!

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