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#50683 04/10/05 10:02 AM
Joined: Jul 2004
Posts: 136
C
cgw Offline OP
Member
A store owner wants the receptacles around the (small) store wired so a switch controls half of the split receptacles. Would you wire the receptacles on one circuit running to the switch first and then to the receptacles with 3 wires (hot-hot-neutral) with one of the hot wire switched? Is it OK to do this with 3 wire cable (e.g. make the red wire the switched wire)? If you were pulling wire in conduit would you use different color for the switched hot?

Joined: Oct 2002
Posts: 482
Z
Member
That's how I do it. If the hot circuit is black, I'd use red or blue for the switched circuit.

Just as good practice, I always run the half hot from a seperate circuit, but on the same phase whenever possible. This way, you aren't putting 240V in reach of a curious kid with a paperclip.

If you can, run an additional neutral, so the outlet is completely split, especially in commercial. It's just good practice, in that commercial demands are usually enough to overload a single (#12) neutral on 2X 20A circuits.

I'd also use 20A devices, including the switch.

=)

Joined: Nov 2004
Posts: 37
J
Member
Zapped, if you are running two circuits off of the same phase and not including a second neutral, then you must oversize the shared neutral. You didn't mention that and I think it's pretty critical information.

Your scenario mentioned about overloading the neutral is not really an acceptable risk to leave open. You either need to wire on separate phases, or use the same circuit, or oversize the neutral.

2 x 20 A on the same phase would require an 8 gauge neutral to handle a maximum of 40 amps.

[This message has been edited by jdadamo (edited 04-10-2005).]

Joined: May 2002
Posts: 132
E
Member
Zapped:

You may want to rethink your idea of another circuit on the same phase that share the same neutral. The neutral is set up to carry the unbalanced load of circuits of different phases but will have an "additive" effect in the situation you have described.

Typical install:

A PHASE= 12A
B PHASE= 12A
NEUTRAL= 0A

Install desribed:

A Phase= 12A
A Phase= 12A
Neutral= 24A

The safest thing one can do in a split-wire receptacle situation is to wire both halves to the same circuit(Phase). IMO.

Joined: May 2002
Posts: 132
E
Member
Man do I type slow huh??

Joined: Mar 2001
Posts: 2,056
R
Member
Outside the situation described in 225.7(B),
using an oversized neutral to carry the sum of the currents on 2 conductors on the same phase would be highly unconventional and impractical, (especially with regard to wiring device installation and box fill), if not necessarily a violation.

Joined: Nov 2004
Posts: 37
J
Member
Yeah don't actually do what I suggested (please...) I agree with Redsy; it's overly convoluted. I was just taking a theoretical stance on what would actually be required to carry that potential neutral load safely.

Joined: May 2003
Posts: 2,876
E
e57 Offline
Member
Outside of the neutral over-load in having two of the same phase and seperate circuits, you'd also have to have one wierd special order handle tie for the breakers. Required by 210.4(B), as written only applies to dwellings, but still not a good practice. Why not just have the on the same circuit?


Mark Heller
"Well - I oughta....." -Jackie Gleason
Joined: May 2003
Posts: 2,876
E
e57 Offline
Member
Anyway cgw, the method you described is fine. One of the areas I work in requires phasing on all power circuits, and seeing that the receptical could be used for other than lighting, they would want the switched wire phased to the color of the circuit. Even though the why I see it, it is not required. It could be any color you want....


Mark Heller
"Well - I oughta....." -Jackie Gleason
Joined: Nov 2002
Posts: 791
W
Member
Quote
Just as good practice, I always run the half hot from a seperate circuit, but on the same phase whenever possible. This way, you aren't putting 240V in reach of a curious kid with a paperclip.

If you can, run an additional neutral, so the outlet is completely split, especially in commercial.

Isn't there a requirement that all circuits feeding the same yoke device be controlled by circuit breakers tied together? Doing that on circuits on the same phase would be a bit hard as most panels have alternating phases on adjacent spaces. Maybe use a breaker meant for 3 phase work, but is that code?

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