I have a simple question for those knowledgable about a simple, but surely common problem. I bought a new 100ft 12 gauge extension cord. With only a few hours on the job I discovered the cord had been accidentally, partially cut by something /someone. How do I safely repair and restore? The nick is into the ground wire, severing 6 of the 50 or so small wires. the larger question I have is: since it wasn’t noticeable while operating power tools for some unknown time what was actually happening to the current, voltage etc? At what point do partially severed wires become how dangerous? What if the nick is in the hot wire? My observations are that many such cords are being routinely used, with disregard?
what say you?
Replies
This is the green wire, right? Just clean the area and wrap 2-3 layers of electrical tape over it. Back in the early days of space exploration, NASA had a soldering school, mainly to get good joints with a minimum of weight. They had some published standards for how many strands you could nick or cut through and still be acceptable.
-- J.S.
Ideally, the ground wire never carries any current at all. If the circuit is protected by a working GFCI, it won't ever carry any current for more than a few microseconds. Without a GFCI, any serious ground fault will trip the breaker. It's possible to come up with a scenario where the ground wire is carrying significant, sustained current, and losing 12% of its capacity would make it overheat dangerously at that point, but in general, I think losing 6 out of 50 strands is probably no big deal. That's if you're talking about the bare or green ground wire. If it's the white neutral wire, you don't want to lose any current carrying capacity at all, especially since 100' is already pretty long for 12 gauge, if you've got much of a load on it.
I would fix it with a crimp on butt splice connector. That way you don't have to shorten the cord to get the ends to overlap. If that conductor is insulated, which it probably is in an extension cord, I would slit the outer jacket back far enough to slip a piece of heat shrink tubing over one of the cut ends before crimping the connector on. The heat shrink should be long enough to cover the connector plus 1/4" or so beyong each end.
For the outer jacket, the traditional fix is black electricians tape and/or duct tape, and if the jacket is just slit, with none of it missing, that may be enough. Any heat shrink tubing you could get on over then plug wouldn't shrink enough to grab the jacket. But you can get heat shrink tape, which shrinks along its length, so you can wrap it snugly around the injured area and then tighten it up with a heat gun.
I know you can get heat shrink tubing with a sealer on the inside that melts at the shrinking temperature to form a water tight seal, and it may also be available for the heat shrink tape. Or you could just clean it up real well and gob silicone caulk all over it.
Or you could cut it at the nick and make 2 cords out of it. Put a gfci at the female end of one and be protected. Your tools will love the lack of voltage drop.
bake
IMHO I think "bake" is right. Get a male and female cord cap, the good ones(About $10 ea.) and cut the cord. You get two reliable cords instead of one where the remaining ground strands, or splice, corrode break or come loose at their leisure and cause a safety hazard. Odds are that a failure won't get you killed but it only has to happen once to ruin your whole day. Do it right and feel good about it.
One small note: Except for a honking great cord I use to get power from distant power poles or generators at job sites I find that a single 50' and two 25' cords in #12 are most effective. Throw in a couple of three way stub cords and you have a very adaptable setup. I have, in a pinch, powered up most of a house from a generator with this kit and run it for most of a week.