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In order to keep a hanging pendant light from falling through the cover plate in the ceiling I tied a knot in the electric wire, as a stopper. Is this safe, or did I just create a fire hazard? If it's unsafe, what can I use as a stopper on the electrical wire of a pendant light?

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I've seen hard plastic wire holders that allow you to create a short loop without actually making a knot on the wire itself. I don't know what they are called (and certainly not in English), but any decent home improvement or home electrical store should have them or know what they are called so you can look online. The cost should be trivial since it's basically just a piece of plastic. –  Michael Kjörling Jan 7 '13 at 9:30
    
@MichaelKjörling I can't find something like this anywhere. If anyone knows of one, please tell me about it –  Dave Jan 7 '13 at 13:55
    
@MichaelKjörling try "zip ties" –  ratchet freak Jan 8 '13 at 0:07
    
@ratchetfreak Actually, that's not what I have in mind, although it should work as well. I've looked but was unable to find a picture; sorry. –  Michael Kjörling Jan 8 '13 at 9:00
    
zip ties didn't work. They didn't get tight enough and the wire could pull right through with minimal effort. –  Dave Jan 8 '13 at 12:23

2 Answers 2

up vote 4 down vote accepted

In the case that the lamp is light weight enough to not stress the cord, there's a specific knot for that called an Underwriter's Knot that is supposed to put minimum stress on the conductors and provide enough bulge to keep it from pulling out. Since most PVC insulation will cold flow under pressure, the edges it butts up against must be well rounded.

Underwriter's Knot

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Isn't this actually supposed to be a temporary measure? The OP seems to be asking for a more long-term solution... –  Pacerier Dec 18 '13 at 6:06
    
The Underwriter's Knot is intended for permanent use to form a strain relief so the wire end connections do not get pulled apart in the lamp socket or out of the plug as it guarantees slack in the tails. Given a couple replacement plugs I've dealt with, it's a really good idea to use it as the clampy-do on most replacement plugs allows the cord to slowly slip out as it's yanked on as the method of removal by your warehouse shop-vac operator. Your first indication something's wrong is to examine the plastic body for melting due to the wire slowly coming loose where the screw holds it down. –  Fiasco Labs Dec 18 '13 at 6:31

It's not perfectly safe, but it's a good temporary solution.

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Why isn't it safe, and what is a permanent solution? Thanks –  Dave Jan 7 '13 at 0:50
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If the wire is under tension, over time the insulation will wear, creating a hazard. –  Jason Jan 7 '13 at 1:46
    
There are suspended lights that use the electrical cable as the suspension element. It is specially made so that the wires don't take the weight. Not a very good idea if its common lamp zip cord. –  Fiasco Labs Jan 7 '13 at 2:24
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@FiascoLabs there are (cheap) lightweight pendant lamps that are designed to hang from the electrical cable. They usually have a compression fitting to prevent the wires from being pulled through. –  Brad Gilbert Jan 7 '13 at 12:57
    
Not too long ago, but not the current version, I saw the NEC state that current carrying conductors should be so arranged as to not support the weight of the fixture. Yet I have seen many such fixtures myself. I'm sure they are not UL listed, but somehow legal for sale in the US. I'm curious how this is possible. I know listing is not required for sale, but non-NEC-complying fixtures? It would explain why such enabling compression gadgets are difficult to find. –  bcworkz Jan 9 '13 at 1:59

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