Robbie Lee
07-28-2015, 1:20 AM
I read an old thread here that I thought was going to clarify this issue, but, alas, it managed to lose me at some point.
Please picture a detached garage containing three 120VAC duplex receptacles. The power for these receptacles comes out of the ground, through the exterior wall (into the garage itself), up the wall (through conduit) and into a steel single hub gang box. After disabling both of the garage breakers, the NEMA 5-20 duplex receptacle was removed from said gang box to reveal a maze of wiring; hence, the word "hub." In short, there a (3) 12 AWG solid copper wires and (1) 12 AWG stranded wire running into this box, which I will refer to as REC A – Black (BLK), Brown (BRN), White (COM) and Green (GND) stranded. NOTE: There is no bare ground wire coming into this box.
As one faces REC A, there is a section of conduit coming out of the left side of the box, which runs straight into another steel single gang box. Pulling the NEMA 5-20 duplex receptacle out of this box, which I will refer to as REC B, reveals (2) 12 AWG solid copper wires and (1) 12 AWG stranded wire – BLK, COM & GND.
As one faces REC A, there is a section of conduit coming out of the top of the box, which runs up the wall, into the open trusses in the garage "ceiling" and into a third steel single gang box, which I will refer to as REC C. Pulling the NEMA 5-20 receptacle out of REC C reveals (3) 12 AWG wires – BLK, COM & BARE COPPER. NOTE: All three wires run out of REC C and into an overhead lighting fixture.
At this point, I'd like to point out that REC A & REC B are protected by a 120V/20A breaker, while REC C (and the rest of the overhead circuit) is protected by another 120V/20A breaker – and BOTH breakers are tied together by a metal jumper/link.
As the owner of this garage is low on cash and needs to convert both REC A & REC B to supply 240V NEMA 6-20 receptacles – to facilitate paying carpentry work – the idea is to employ the BLK wire and the BRN wire as HI wires for REC A, and, as REC B is already wired to the hub, the BLK and the COM wires running between REC A (the hub) & REC B will automatically provide 240V for a second NEMA 6-20 receptacle.
At this point, all seems fairly clear to me. The problem comes in when I'm asked about how to best supply the overhead circuit, which supplies the NEMA 5-20 receptacle and the overhead lighting with 120VAC. I've known the owner of the garage in question my whole life and, yes, I gave him all the obligatory warnings and advice about installing a separate 120V circuit for the overhead devices, but he simply doesn't have the cash for it. Despite my advice, I know that he's going to use what he has on hand, so I'd like to make this "economy conversion" as safe as it possibly can be.
My idea was to attach the BLK wire – which is already running up to REC C – to the top screw on the new NEMA 6-20R and into a economical (small) sub breaker panel containing one 120V/20A breaker – which will be installed between REC A (the hub) and REC C (overhead). The COM wire will pass directly through REC A and be attached to the COM bar in said sub panel. Not to state the obvious, but the BLK, the COM and the BARE leads/wires will continue on up to the 120V overhead circuit.
Although I retired from the electrical field, I'm not a licensed electrician. I'm a childhood friend of the guy asking [me] for advice, though, so I thought I'd ask the forum board for constructive thoughts about my idea before offering any final advice. If I could be there myself, I would. I'm out of state, however, so it's nearly impossible right now. By the way, I'm very interested in why the electrician tied the two 120V/20A breakers – presently supplying the garage – together with a metal link/jumper.
Thanks very much for your time,
Rob Lee
Please picture a detached garage containing three 120VAC duplex receptacles. The power for these receptacles comes out of the ground, through the exterior wall (into the garage itself), up the wall (through conduit) and into a steel single hub gang box. After disabling both of the garage breakers, the NEMA 5-20 duplex receptacle was removed from said gang box to reveal a maze of wiring; hence, the word "hub." In short, there a (3) 12 AWG solid copper wires and (1) 12 AWG stranded wire running into this box, which I will refer to as REC A – Black (BLK), Brown (BRN), White (COM) and Green (GND) stranded. NOTE: There is no bare ground wire coming into this box.
As one faces REC A, there is a section of conduit coming out of the left side of the box, which runs straight into another steel single gang box. Pulling the NEMA 5-20 duplex receptacle out of this box, which I will refer to as REC B, reveals (2) 12 AWG solid copper wires and (1) 12 AWG stranded wire – BLK, COM & GND.
As one faces REC A, there is a section of conduit coming out of the top of the box, which runs up the wall, into the open trusses in the garage "ceiling" and into a third steel single gang box, which I will refer to as REC C. Pulling the NEMA 5-20 receptacle out of REC C reveals (3) 12 AWG wires – BLK, COM & BARE COPPER. NOTE: All three wires run out of REC C and into an overhead lighting fixture.
At this point, I'd like to point out that REC A & REC B are protected by a 120V/20A breaker, while REC C (and the rest of the overhead circuit) is protected by another 120V/20A breaker – and BOTH breakers are tied together by a metal jumper/link.
As the owner of this garage is low on cash and needs to convert both REC A & REC B to supply 240V NEMA 6-20 receptacles – to facilitate paying carpentry work – the idea is to employ the BLK wire and the BRN wire as HI wires for REC A, and, as REC B is already wired to the hub, the BLK and the COM wires running between REC A (the hub) & REC B will automatically provide 240V for a second NEMA 6-20 receptacle.
At this point, all seems fairly clear to me. The problem comes in when I'm asked about how to best supply the overhead circuit, which supplies the NEMA 5-20 receptacle and the overhead lighting with 120VAC. I've known the owner of the garage in question my whole life and, yes, I gave him all the obligatory warnings and advice about installing a separate 120V circuit for the overhead devices, but he simply doesn't have the cash for it. Despite my advice, I know that he's going to use what he has on hand, so I'd like to make this "economy conversion" as safe as it possibly can be.
My idea was to attach the BLK wire – which is already running up to REC C – to the top screw on the new NEMA 6-20R and into a economical (small) sub breaker panel containing one 120V/20A breaker – which will be installed between REC A (the hub) and REC C (overhead). The COM wire will pass directly through REC A and be attached to the COM bar in said sub panel. Not to state the obvious, but the BLK, the COM and the BARE leads/wires will continue on up to the 120V overhead circuit.
Although I retired from the electrical field, I'm not a licensed electrician. I'm a childhood friend of the guy asking [me] for advice, though, so I thought I'd ask the forum board for constructive thoughts about my idea before offering any final advice. If I could be there myself, I would. I'm out of state, however, so it's nearly impossible right now. By the way, I'm very interested in why the electrician tied the two 120V/20A breakers – presently supplying the garage – together with a metal link/jumper.
Thanks very much for your time,
Rob Lee