Can I run wires from two separate circuits through the same box, if one of those circuits is just passing through (no connections)?
I have a switch in the basement which is currently wired to outlets in the room and I want to change it to switch the overhead light instead.
I know how I would go about wiring it. The diagram shows how the room is currently wired. What I will do is remove all wires from the switch twist the two black (live) wires together with a nut and remove the pigtailed ground from the switch (and the box). That leaves those outlets all normally powered without a switch.
This wiring diagram belongs to do-it-yourself-help.com. The original can be found here: https://www.do-it-yourself-help.com/outlet-switch-electrical-diagrams.html
Now my question is, can I just leave those wires in that box even if I am going to run wires from the light into that box, and to that switch? The light is powered from wires on a different circuit, so I will have two sets of wires from two different circuits running through that box.
It seems okay to me, although it's not clear if I am breaking regulation codes by having two circuits so close together. I know you will likely tell me it will depend on where I am (Alberta), but I would rather err on the side of safety. Would you do this, yourself? If not, how would you properly route the existing wiring around the switch? I know that wherever I choose to splice those wires, they need to be in an accessible box.