I have just installed a brand new 200 A panel and wired 27 circuits in an addition to our home. I applied energy to each circuit in turn by setting the breaker and one of the lighting circuits (15A) tripped immediately. To troubleshoot, I switched each of the wall switches on the circuit one at a time and reset the breaker after each trial. I tripped the breaker perhaps five times within 2 minutes.
I finally found the short (line to ground caused by aggressive tightening of the cable clamp in one of the boxes coupled with a small burr on the inside of the clamp).
A new problem, and the reason for this post, is that the breaker (Square D QO series) was leaking voltage when it was off. With the breaker in place, turned on and the line physically disconnected, I read 120 volts from the neutral bus to the line terminal on the breaker, as I would exect. With the breaker off, however, I read 60 volts from the bus to the terminal, which I would definitely not expect.
Thinking that the frequent tripping may have created a high resistance path through the breaker, I pulled it and idly flipped it on and off a few times before checking the resistance. Breaker off, resistance infinite, breaker on resistance 0. I reinstalled it and now find that it works properly, not leaking any voltage while it is off.
Does anyone have a plausible explanation?
Thanks in advance
David