I wired my finished basement myself. In general everything was fine, I had
it inspected before insulating walls and ceiling and putting drywall. I have
been using power in basement for over the year and nothing was wrong.
However, on final inspection the electrical inspector and I found a very
weird problem that I need now to correct. I have the following wiring
diagram in basement:

- dedicated 20 A circuit to basement lighting, total 26 recessed lights 65 W
and 50 W
- dedicated 20 A circuit for basement rooms receptacles
- dedicated 20 A circuit for sump pump
- dedicated 20 A circuit for washer / gas dryer
- dedicated 20 A circuit sewer ejector pump
- dedicated 20 A circuit for basement bath
- dedicated 20 A circuit for garage receptacles
- 50 A basement workshop sub-panel powering 5 dedicated 115 V / 20 A, 2 220
V / 20 A shop receptacles circuits, and 1 15 A shop lights circuit

When I switched off basement room receptacles circuit breaker while all
others except sub-panel which does not seem to affect the problem were on we
found there is 8 V power in that circuit. Switching off some of other
circuits reducing this voltage to about 2 V and only switching off all new
circuits brings disconnected voltage to zero as it should be.

Can anyone give me a clue what cane be a source of this weird residual
voltage in disconnected circuit?