I was planning on installing a programmable timer on one of the 4 single-pole switches on a circuit. All of the 4 switches control various lights towards the front of the house, one of which is a pair (2 pairs actually) of motion-sensor lights.
After turning off the breaker for the circuit that controls these 4 switches, I used a non-contact voltage tester to make sure everything was cold, but to my surprise I found that the live wire still made my tester chirp and alert me of a low voltage presence (i.e.2 out of the 6 leds on the tester lit up). I then proceeded to switch off more circuits at the breaker, and eventually the tester stayed silent when I tested the live wire again.
I'm obviously a novice but have done a bit of reading up before posting here. I've read a bit about "induced voltages" that show up as a result of other live wires being in proximity to the wires in the circuit in question. I've also read about "backfed voltages" that are a result of equipment on the circuit (I know some motion sensor light have capictors in them..) or are the result of other circuits.
Since the low voltage disappears when I turn off some of the other circuits, I'm still left questioning what the culprit is...and if I need to be worried at all? The reason I'm worried, is because my timer requires a neutral. So, if the culprit is of the backfed variant (specifically from other circuits) I don't know if that impacts tying into a neutral (or does it not matter in any case)?
I'm not sure the image helps at all...but I figured people always like pictures. Am I overthinking this all, or can I just tie into the bundle of neutrals (circled) regardless of why there's low voltage on live (yellow highlight) with the circuit breaker off.