Surprise Shock

[Eddie_T]

I was troubleshooting a 3-way switch circuit for a friend. It was in a detached building classified as a garage but more of a man cave. The electrician that wired the building left wires too short to reach receptacle and switch screws so back stab connections were used. I was trying to determine if there was a switch problem, improper installation or a loose carrier wire.

I pulled the panel disconnect for the building, the lights went off and I was trying to get some slack in the wire when I got a shock. I could measure voltage on all three switch screws but didn't have a suitable wire to ground the circuit. I closed it up deciding to think it through. My guess is energy storage in the fluorescent circuitry but lack any experience there. I may to try to make a coat hanger wire tool to release stab connections for switch removal. If I do remove the switch I plan to lengthen the wires so screw connections can be used. I may just leave well enough alone as he doesn't really use the 3-way function.

Apparently only one carrier wire has continuity as I have it configured so he can turn the lights on/off from either switch but not on with one and off with the other.

 

[ctviggen]

Did you test it with a voltmeter? I would think that any residual energy would dissipate fairly quickly.

If you turn the light on with one switch, what happens when you flick the other switch? Do they both have to be in the off position for it to go off?

 

[afjes_2016]

EddieT if you got a shock after shutting off the disconnect then there is still power going to the building. Although feeding a detached building with more than one circuit is against code it does not mean it was not done.

If this is a 3 way switch setup it should not have changed since the electrician wired it up (if it was wired properly). Maybe one of the switches is bad in the 3way setup. That would make more sense to me than something being wrong with the setup - that is if the setup worked in the past.

Also, just for "giggles" do either of the 3 way switches have imprinted on the switch itself "On" or "Off"? Which they should not have on them. I am assuming that this setup had never worked with this question.

 

[Eddie_T]

The only mystery is the residual voltage. If not for the shock the troubleshooting would have been a simple matter. There was a bad FL tube (flickering) which may (or not) have contributed to the mystery residual voltage. He has replaced the FL tubes. He built the building and there is no other power source.

I was over there today for supper and the owner says it's fine as he never enters by one door and exits by the other. The rear door is an overhead garage door mostly for code purposes but also handy for moving large items in/out.

If he ever wants it fixed I'll take my neon tester to verify that the residual is DC and if so just discharge it to ground. I expect the circuit problem to be; it never worked (miswired), bad switch or loose stab connection for one of the carrier wires.