A scary discovery, what's going on?

[George Yetka]

Pre-twisting provides a very positive connection, IMHO. I've also now moved to Wago connectors, but if I do a wire nut, I always pre-twist with lineman's pliers, clean/trim the end and then apply the wire nut followed by tape.

It will be interesting to see what you find when you peel that apart to see why it's arcing.

Ive been told by Electricians(more than 1) on the job that wagos are no good, they eventually come loose. I have not witnessed this and do use them myself. It may be a pipefitter doesnt like propress because it takes my work situation though.

[Wayne Cannon]

The insulation material on the stranded material may have a lower melting point in addition to less thermal mass. Just a thought.

[Jim Becker]

Ive been told by Electricians(more than 1) on the job that wagos are no good, they eventually come loose. I have not witnessed this and do use them myself. It may be a pipefitter doesnt like propress because it takes my work situation though.

I don't see them coming loose with the tape wrapped around them, but un-taped, the little tabs could release when one is pushing them around in the box. Most of those I've used are in "yuge" boxes which feed out to machine locations, so it's not a tight space. I'm not personally worried about them. A number of electricians around here use them and when I asked the electrician who installed my service, he offered no cautions.

[roger wiegand]

Given the number of failures of joints made with wire nuts I've seen personally over a couple decades of home renovations the Wago's would have to be pretty terrible to be worse. They seem less subject to user error in installation (I just received my first box of lever lock Wagos, haven't used any yet). There's a phenomenon with almost every new technology where someone's uncle's brother in law heard of a failure of the new product and now everyone thinks it's junk. The introduction of PEX would be a good example, or the utter nonsense that circulates about electric cars. Of course the stories of polybutylene and cPVC water pipes might be a good counterexample. The lever connectors have been used since 2003, if they failed at an unusual frequency I think the NFPA/code folks would have noticed by now.

[Ken Fitzgerald]

A few weeks ago, I lost a ballast in one of the 15, 4 bulb T-8 lights in my shop. When I replaced the ballast, I discovered the Wago connects. In my 40+ years servicing everything from radars used in air traffic control to CT and MR scanners, I used a lot of twist on connects. I like the Wago connectors!

[Michael Burnside]

Ive been told by Electricians(more than 1) on the job that wagos are no good, they eventually come loose. I have not witnessed this and do use them myself. It may be a pipefitter doesnt like propress because it takes my work situation though.

My friend is an electrician and uses them all the time. He says they are great for tight places and are code approved. We used them in my shop for the 240V because they are a lot cleaner when wiring 10 or 8 gauge wire. They're not coming lose any more than a properly installed wire-nut with the ends pre-twisted beforehand.

[Cameron Wood]

I'm no electrician but I don't think you want tinned wire in a compression connection. I've personally seen two equipment failures (one very expensive) due to a tinned, stranded wire being installed in a screw terminal (i.e., compressed under a screw head). The solder will creep over time and cause the joint to fail. I don't know if this applies to a wire nut also, but since it's a compression fitting as well I would err on the side of not tinning stranded wire.

No idea why your wire melted though!

I disagree with this- stranded wire wrapped under a screw head is a mess and tinned is better. Likewise tinned stranded wire is better in a wire nut or in a crimped connector (but matters less there).

I've used Wagos and have somewhat mixed opinion. Good for switch boxes (they take up less room, not more), and fine for connecting a light fixture, but they are basically the same mechanism as push in connections on the back of household switches and receptacles, which while approved, are the cause of many electrical problems and something that I never use.

(I am an electrician- well, general contractor with 45+ years in electrical)


The missing strands that were cut in stripping is not a factor, IMO. Wire connections in switch boxes often get compromised from pushing the wires back into the box, especially if they were not planned to go in without stress. I never tape wire nut connections- just makes a sticky mess and doesn't add anything. Never see it in professional installations. Since your load is up there & there's been a problem, it would be good to check the current draw- lots of clamp on units around for borrow or buy.

[Dan Friedrichs]

Since your load is up there & there's been a problem, it would be good to check the current draw- lots of clamp on units around for borrow or buy.

If that were the root cause, why was the wire out the other side of the switch not affected?

[Cameron Wood]

If that were the root cause, why was the wire out the other side of the switch not affected?

Probably because the wire nut connection was better. I don't think the high draw is the root cause, but could be contributing. If the load was less, maybe the wire would not have overheated, in spite of a poor connection.

[Jim Becker]

I've used Wagos and have somewhat mixed opinion. Good for switch boxes (they take up less room, not more), and fine for connecting a light fixture, but they are basically the same mechanism as push in connections on the back of household switches and receptacles, which while approved, are the cause of many electrical problems and something that I never use.

While I agree with never using push-in connections on switches and outlets, Wagos are not quite the same. While you "can" use them as push in, if you flip the lever, you can easily insert the bare wire end and then put the clamp in place positively so it bites as it's supposed to do. The wire remains nearly pristine. You do have the advantage of disengaging a wire if you need to by flipping the lever to release it. Of course, that's also why I recommend taping them, too.

[Cameron Wood]

While I agree with never using push-in connections on switches and outlets, Wagos are not quite the same. While you "can" use them as push in, if you flip the lever, you can easily insert the bare wire end and then put the clamp in place positively so it bites as it's supposed to do. The wire remains nearly pristine. You do have the advantage of disengaging a wire if you need to by flipping the lever to release it. Of course, that's also why I recommend taping them, too.

Actually, the ones that I have mainly used are another brand, & don't have the lever- similar to what comes preinstalled on recessed light cans these days.

[Ron Selzer]

Roger, I believe the device failed internally increasing the resistance resulting in high amperage needed to provide required amperage out to lights. I base this on a situation back in the 1990's on a Chiller feed with 4/0 wire to a circuit breaker, factory provided on the Chiller. The insulation melted back on the wire feeding the circuit breaker, one of three, the wire leaving the circuit breaker was never damaged. I had installed 3 split core current switches per control drawings. Once the chiller ran for less than a day, I had to use a hammer to break the melted plastic cases to remove the current switches. Only after the circuit breaker was changed out did the wire remain undamaged. there was a measurable voltage drop thru the circuit breaker when the chiller was operating.

[roger wiegand]

Another interesting idea. The switch is still working fine, I can measure the resistance.

Roger, I believe the device failed internally increasing the resistance resulting in high amperage needed to provide required amperage out to lights. I base this on a situation back in the 1990's on a Chiller feed with 4/0 wire to a circuit breaker, factory provided on the Chiller. The insulation melted back on the wire feeding the circuit breaker, one of three, the wire leaving the circuit breaker was never damaged. I had installed 3 split core current switches per control drawings. Once the chiller ran for less than a day, I had to use a hammer to break the melted plastic cases to remove the current switches. Only after the circuit breaker was changed out did the wire remain undamaged. there was a measurable voltage drop thru the circuit breaker when the chiller was operating.

[Lee Schierer]

To me it looks like the failure was a really cheap and undersized wire nut. Note that the wire nut that failed is smaller than the others in the box. Most likely it was the wire nut supplied with the switch intended for connecting the switch to a single wire, not gripping the three wires of the connection.Attachment 504137 Attachment 504138

[Ron Selzer]

Another interesting idea. The switch is still working fine, I can measure the resistance.

Should not be able to measure any resistance thru the switch as this will indicate a voltage drop condition and amps being used to generate heat.