ECN Forum
Posted By: cgw Wiring split receptacles. - 04/10/05 02:02 PM
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?
Posted By: Zapped Re: Wiring split receptacles. - 04/10/05 02:13 PM
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.

=)
Posted By: jdadamo Re: Wiring split receptacles. - 04/10/05 02:24 PM
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).]
Posted By: elektrikguy Re: Wiring split receptacles. - 04/10/05 02:35 PM
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.
Posted By: elektrikguy Re: Wiring split receptacles. - 04/10/05 02:37 PM
Man do I type slow huh??
Posted By: Redsy Re: Wiring split receptacles. - 04/10/05 02:41 PM
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.
Posted By: jdadamo Re: Wiring split receptacles. - 04/10/05 03:28 PM
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.
Posted By: e57 Re: Wiring split receptacles. - 04/10/05 03:48 PM
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?
Posted By: e57 Re: Wiring split receptacles. - 04/10/05 03:56 PM
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....
Posted By: wa2ise Re: Wiring split receptacles. - 04/10/05 07:48 PM
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?
Posted By: cgw Re: Wiring split receptacles. - 04/11/05 02:43 AM
I think I will just use one circuit and split it up. Actually my wife owns a gift shop (not the one we are talking about). She uses the circuit breakers to turn off receptacles which have things like lamps, and display lighting. 3 or 4 split receptacles on a circuit should be fine. I will make them 20A. I would want to have a different color switched wire just to keep it simple.
Posted By: Zapped Re: Wiring split receptacles. - 04/12/05 02:29 AM
Ummm, did you guys read the third paragraph?
Posted By: Spaceman Re: Wiring split receptacles. - 04/14/05 11:45 AM
To keep it simple, just use one single-pole breaker and switch one wire of a 12-3 cable. Then you will not overload the neutral.
Like this: breaker-black-switch-red then wire the outlets with a common Neutral and split the black and red on the top and bottom.

The switched outlet is on the bottom so the switched cord will not hang in front of the hot outlet which will then be easer to use, since the switched cord will most likely stay plugged in all of the time. (Whew! out of breath.)
Posted By: boggerbutt2454 Re: Wiring split receptacles. - 04/14/05 10:52 PM
Don't forget when you have two circuits on a single yoke you are required to use a two pole breaker so that you shut both circuits off at the same time. Don't think having circuits on the same phase would be legal NEC even with larger neutral.
© ECN Electrical Forums