About a year ago, I wired and obtained service for a small barn I have. This is not my first electrical project, however I've created some sort of problem that has me baffled.

Have a very simple light circuit that keeps failing,, destroying switches. Basic circuit, power from the pannel, to a switch, 4 100w incadecent light bulbs in porcelan fixtures in the circuit. (installed in a barn) I've checked that wires are on the correct terminals in each light (black on brass). I have the black as the switched wire on the sw. However on a average of 2 to 10 cycles of the switch, the switch fails.

If I turn on the circuit, I can leave on for many, many hours. All is good, no heat anywhere, circuit never fails.

Have 2 other circuits in the barn. A 20 amp outlet circuit,, never has any problems. And a 22ov 50amp, it also works fine.

There should be no problem with a 120 volt circuit and 400 watts of load.

What type of switch are you using? Brand and model #.

Need to confirm switch is rated for the proper voltage and load.

A switch fails and you replace it? Several switches of the identical brand and model have failed?


Does the switch get wet?

Lloyd
Did you resolve your problem? It is too unusual to just let fade away. Inquiring minds want to know.

It would be good to check current with an amprobe, Shouldn't be failing as mentioned, could be a bad batch of switches, try a 20 Amp switch.

Thanks for the replys, sorry been away for a few days. I've tried 2-3 different switches, and 2 of them were 20amp $6 switches from Home Depot. They lasted a few more cycles, however in the end they died as well.

I thought well maybe I have a bad peace of wire. So I did this. I broke the circuit in 2. Wired 2 porcelin fixtures on one end of the barn with one switch, did the other 2 with a different switch. Installed them in a double box, fed them from the same circuit pannel breaker. To be clear, one wore from the pannel, do a double box, with 2 separate switches. From each switch to 2 100 watt bulbs.

Guess what?? Less than 10 on/off cycles... both switches failed. I thought maybe by doing this I'd have 1 fail, and locate the problem to one or the other circuit. Instead, I think I found out that it must be a problem in the feed from the pannel? Because they both failed and it is all they share in common?

This is just weird!

Thanks for your help!

I'm, with Strat, you need to start checking amperage and voltage.

First thing I would do is check the voltage between the two switch terminals on with the switch in the off position. Check voltage between incoming hot and ground and between hot and neutral. Next I'd check the amperage on the line with the switch on.

This is single phase service isn't it.

You said

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About a year ago, I wired and obtained service

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Is this a new and separate service or is it really just a sub panel off you main panel?

You need to describe exactly how the circuit is wired.
Perhaps you need to describe how your panel is wired also. Is that circuit the only thing on that leg of your service. Could try moving circuit to other leg.

Next I'd break one of the switches apart and see what is happening inside.

You stated that you have left the switch on for an extended period therefore I do not suspect amperage. I suspect a high voltage is arcing the contact points when the switch is off. High amperage would cause contact spring or mechanism to melt.

Have no explanation for why high voltage would not blow bulbs.

hkstroud
"Next I'd break one of the switches apart and see what is happening inside."
I used to take everything broke apart.
I took apart 1 failed switch apart and found it caked with ants. You couldn't fit another ant in there, they were packed so tight.
Another Time, I went to check out someone's cooktop. They said each of the 4 elements failed one by one. Took them apart and found each caked with ants.
I think they all went to 1 control for the warmth of the indicator, when that one failed and the next one was used, more ants went to the second one and so on till all 4 went bad.
All controls had ants.
Must have been Wimp ants as I live in South Florida, or they are just spoiled(used to sunny days).
This was during the Winter.

Maybe they were just "cordless" ants and needed to be recharged.

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Originally Posted by Stratmando

Hkstroud
"Next I'd break one of the switches apart and see what is happening inside."
I used to take everything broke apart.
I took apart 1 failed switch apart and found it caked with ants. You couldn't fit another ant in there, they were packed so tight.
Another Time, I went to check out someone's cooktop. They said each of the 4 elements failed one by one. Took them apart and found each caked with ants.
I think they all went to 1 control for the warmth of the indicator, when that one failed and the next one was used, more ants went to the second one and so on till all 4 went bad.
All controls had ants.
Must of been Wimp ants as I live in South Florida, or they are just spoiled(used to sunny days).
This was during the Winter.

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Bringing this old thread back to life...

Moved into our place about 3 years ago. One of the light fixtures in the garage didn't work, changed out the switch and voilà. Same fixture died on me last week, tested and found switch was faulty again. Replaced and tossed the old one.

Wondering about it so did a quick search on Google and found this thread, in particular, this bit about ants (since we had trouble with tiny ants a few years back). Dug the switch out of the garbage, took it apart and boom, full of ants.

Signed up just to share, thanks for the info

Thanks for sharing. Sometimes, when things don't apprear to be logical, you just have to keep digging until you find the cause.

Cool.

We had some Very Bad rains down here about a month or 2 ago, had several Gate repairs and found the smallest of Ants in one of the limit switches. They also built a big mound and loaded with ants and eggs in the Control Box, I used bug spray.
One company suggested a Flea coller in the Control Panel Enclosure?

That's a great idea Strat. I've had problems with ants in the control switch of a water well.

Thanks for posting. We have a switch that keeps failing on a wall where we know we have an ant problem. This explains it. Now, the next question is how to keep the ants out of the switch??

Put a plastic bag over it. Twist bag around pipe and wires, wrap with electrical tape to seal.
OR
Seal all unused holes and openings with tape or caulking,
Seal where electrical cable enters the box with caulk, seal between the cover and base with electrical tape. Put small "O" ring under nut that holds cover down.

Flea Collar has been mentioned by one of my companies.

I have the very same problem, a simple light circuit with repeated switch failure. I can even hear the switch arcing sometimes. I have replaced the switch 4 times now, and can find no other problem. I have used heavy duty 20 amp switches eveery time. (I like to wire things heavily) I did some searching on the internet and found a few threads that blame Chinese made Leviton switches. I ssearched and found an American made Cooper switch, but I have the same problem again. I took the last switch apart but found no ants or anything unusual inside. I am stumped. (And frustrated!)

Just an update. I just replaced the switch again. I opened it up and I did find a few ant bodies in there. Not many, but a few clustered around the actual contact. I didn't notice that in past examinations. I might have mistaken it for the results of arcing. So I think I have an answer. I sprayed the switch box with bug spray, but I just read about the flea collar trick and I think I will try that. I am really tired of changing this switch! My next question is this. Since there are two switches in that box for different circuits, why do the ants only invade one of them? I have never had to change the second switch in that box! Thanks folks for your insights!

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Originally Posted by hudgek

Just an update. I just replaced the switch again. I opened it up and I did find a few ant bodies in there. Not many, but a few clustered around the actual contact. I didn't notice that in past examinations. I might have mistaken it for the results of arcing. So I think I have an answer. I sprayed the switch box with bug spray, but I just read about the flea collar trick and I think I will try that. I am really tired of changing this switch! My next question is this. Since there are two switches in that box for different circuits, why do the ants only invade one of them? I have never had to change the second switch in that box! Thanks folks for your insights!

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I don't know about the wisdom of aerosol insecticides around electric contacts, as most aerosols use a petroleum product solvent. If it hasn't blown yet, I hope it won't. As to why ants go to one contact instead of another, two possibilities exist. 1) If the circuits use separate conduits, the ants have only "marked" one. They follow a scent trail laid down by the foragers. 2) If only one conduit carries both circuits, likely there is an inefficiency causing some waste heat that attracts the ants. A fraction of a degree is sufficient.

I was a little worried about the bug spray shorting things out. I removed the switches and just sprayed the box itself. So far, no problem. Time will tell, I suppose.

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Originally Posted by hudgek

I was a little worried about the bug spray shorting things out. I removed the switches and just sprayed the box itself. So far, no problem. Time will tell, I suppose.

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Most aerosol ant sprays last about 2 weeks. Sealed up in the box you might get a month. Figure out where the anthill is, outside or underneath or maybe in a gutter that hasn't been cleaned, apply a granular ant bait around it, and your troubles with them should be over before it's time for more spray.