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I was changing some outdoor lights. I had the circuit breaker off (which stopped the lights from working) and the switch off. I used a contactless circuit tester and a testing screwdriver which suggested there was no current.

When working on the live wire I felt a slight buzz - not strong enough to call it a shock - so I shorted it to ground with a screwdriver and there was a spark. After that there is no more buzz from the wire and nothing tripped.

Given the circuit breaker is off how was it possible to get a very small shock from the live wire? Is it residual charge in appliances on the circuit discharging? Is there anything one should do when working in this situation?

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    How big of a spark? Tiny blue? Or OMG I can't see anymore white? – Harper - Reinstate Monica Jan 11 '20 at 3:14
  • It was a very slight buzz, a tingle. The spark was also very small. – Ben Jan 22 '20 at 13:19
  • Well, that's a load coming on, then... not a short to ground. I would say that any advertised claims about the breaker being off are highly exaggerated. – Harper - Reinstate Monica Jan 22 '20 at 18:33
  • Would it not continue to give a buzz if the board remained as it was? Once it was shorted it was totally benign and nothing tripped or changed on the board. That is what is so confusing! – Ben Jan 24 '20 at 17:10
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I would be looking at a multi wire branch circuit that was not handle tied OR possibly someplace the neutrals for 2 circuits got mixed up. Kind of the same thing but if the neutral was returning current from a different breaker you have turned off you could get a shocking experience, I have found both issues in the past and that is where I would be looking.

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    That's exactly how I found out about MWBC's in my younger years.+ – JACK Jan 11 '20 at 0:12
  • Thanks for the suggestion. Would it not continue to give a shock / spark? Or would the symptoms stop after it had been shorted? That's why I don't think it is a neutral issue - but I very much could be wrong as I'm clearly no expert in this. – Ben Jan 22 '20 at 13:20
  • It would depend on the load on the other circuit if a mwbc , many years back handle tied were not required and I got zapped a few times at first I thought it was “static” or some kind of “phantom voltage” until tracing it back and found a mwbc with no handle tie. The next time I was sure it was a mwbc and it ended up being 3 circuits with neutrals mixed up in a switch setup. I have seen these issues many times since. As far as phantom voltages I have seen voltage but never enough current to have a flash as 120v is the max voltage to ground (in US). static shocks are usually thousands of volts. – Ed Beal Jan 22 '20 at 14:14

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