mikewillnot
Member
- Location
- Rochester, NY
- Occupation
- electrical contractor
This is coming up all the time lately for us. Referencing 225.30 (2017) here.
Typical situation: Existing detached garage, with existing (old, underground) conductors for power AND for switching light(s) on garage from inside house -- usually on (1) 15a circuit, usually no other house loads.
We are adding a feeder to garage for new EV loads in new conduit, sometimes 60 amps, sometimes more, with a new sub-panel in garage.
Customers generally want to maintain switching from inside house.
225.30 says one branch circuit or feeder per detached building, with some exceptions. The only thing I see relevant is 225.30(D), for lighting controls, which would require "special permission." Seems like that would/should apply to a much larger, complex kind of detached building scenario.
If I just leave that switching (lighting controls) part of the circuit alone, and separate out the other garage loads and feed them from the sub, does either the original control wiring or the new feeder count as a second feed or branch circuit?
And actually, this brings up the question: Is lighting control wiring like this permitted at all???
I have to assume it is/was legal only if the whole garage, including outlets & lights (whether switched in house or in garage) is/was on a single (or multi-wire) branch circuit in the house main panel.
225.30 ALSO says, in a second paragraph, that "Where a branch circuit or feeder originates in these additional buildings... only one feeder or branch circuit shall be permitted to supply power back to the original building or structure..."
This suggests a solution, essentially that everything in the garage, including lighting and the switched part(s) of the circuit, gets power from the sub, though it seems strange:
HOUSE SERVICE -> Garage Sub -> [lighting circuit] back to house switch / 3 wires (B/R/W) / with switched red returning to garage for garage lights.
I can see doing this in new construction. With an old house, though, and an existing switch with a mess of old wiring, it could get hairy.
This is a bit of thinking out loud. I'd be very interested in comments or suggestions. THX
Typical situation: Existing detached garage, with existing (old, underground) conductors for power AND for switching light(s) on garage from inside house -- usually on (1) 15a circuit, usually no other house loads.
We are adding a feeder to garage for new EV loads in new conduit, sometimes 60 amps, sometimes more, with a new sub-panel in garage.
Customers generally want to maintain switching from inside house.
225.30 says one branch circuit or feeder per detached building, with some exceptions. The only thing I see relevant is 225.30(D), for lighting controls, which would require "special permission." Seems like that would/should apply to a much larger, complex kind of detached building scenario.
If I just leave that switching (lighting controls) part of the circuit alone, and separate out the other garage loads and feed them from the sub, does either the original control wiring or the new feeder count as a second feed or branch circuit?
And actually, this brings up the question: Is lighting control wiring like this permitted at all???
I have to assume it is/was legal only if the whole garage, including outlets & lights (whether switched in house or in garage) is/was on a single (or multi-wire) branch circuit in the house main panel.
225.30 ALSO says, in a second paragraph, that "Where a branch circuit or feeder originates in these additional buildings... only one feeder or branch circuit shall be permitted to supply power back to the original building or structure..."
This suggests a solution, essentially that everything in the garage, including lighting and the switched part(s) of the circuit, gets power from the sub, though it seems strange:
HOUSE SERVICE -> Garage Sub -> [lighting circuit] back to house switch / 3 wires (B/R/W) / with switched red returning to garage for garage lights.
I can see doing this in new construction. With an old house, though, and an existing switch with a mess of old wiring, it could get hairy.
This is a bit of thinking out loud. I'd be very interested in comments or suggestions. THX
