kitchen 12/3 GFCI options

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  #1  
Old 01-26-05, 02:37 PM
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kitchen 12/3 GFCI options

California, U.S. re: providing GFCI protection to a pair of new 20A kitchen appliance circuits.

Can the GFCI requirements be satisfied with a single GFCI outlet on each circuit protecting all remaining circuits downstream? If not, what would be pros/cons of: A) standard dual breaker w/ individual GFCI outlets, versus B)
dual GFCI breaker w/ standard outlets. Does the SEC state a preference?

Thanks
 
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  #2  
Old 01-26-05, 03:23 PM
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One GFCI per circuit is sufficient. But the way you ask your question (mentioning double-pole breakers) suggests you may have a multiwire circuit using 12/3 cable. Multiwire circuits introduce extra complications with regards to GFCI.

One GFCI receptacle plus one standard breaker is usually cheaper than one single-pole GFCI breaker, and they both provide the same protection. So when multiwire circuits are not involved, you almost always see the GFCI receptacle.

If you have a multiwire circuit, you probably need to use the double-pole GFCI breaker, unless you separate the circuits prior to the first outlet. Or if the number of outlets is small, you could also just use a GFCI receptacle in every outlet. But if you haven't installed it yet, I highly recommend two runs of 12/2 rather than one run of 12/3.
 
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Old 01-26-05, 06:56 PM
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Hi John, thanks for the info. I wonder if I can ask a follow up, as perhaps I didn't give enough information...

This is a remodel and a 12/3 is already available, had hoped to re-use it. Though it would be possible with some work to re-run 2 12/2's in its place, if necessary. No GFCI in prior install.

The "anticipated" wiring scheme was to leapfrog red/black circuits from receptacle to receptacle. (a single duplex receptacles would be in only one circuit, not split top/bottom between both) 8 total receptacles, 4 on each circuit.

The plans I've seen for such layouts always seem to show a separate GFCI at each outlet. Is that required, given this particular wiring?

I guess what I'm wondering is if the shared neutral confuses things with the GFCI, so the downstream protection type layout can't really work if either circuit may be leaking onto the neutral and tripping the GFCI.

And if individual GFCI's are required, then it starts seeming like the GFCI breaker might be more cost effective than 8 receptacles, though I haven't priced it out yet.

And if you have the time to comment on it: are there any other reasons you'd prefer 2 12/2's over a 12/3? Or anything else that sounds like a red flag in this wiring plan? If red/black circuits are properly connected to opposite poles, is there still any downside to the shared neutral?

Thanks again
 
  #4  
Old 01-26-05, 07:22 PM
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I always miss information that is only in the title and not in the post.

Here are your options:
(1) Use a somewhat expensive and somewhat hard to find 20-amp double-pole GFCI circuit breaker. If you do this, then you can do pretty much anything you want in the kitchen, including the leapfrogging approach you mentioned. You could even split the receptacles top and bottom.

(2) Use a GFCI receptacle in every box, using only the line-side connections and none of the load-side connections. This is almost as flexible, and could be more or less expensive than the previous option depending on how many outlets you have. You can still do the leapfrog, but you can't split-wire each receptacle.

(3) Split the multiwire before the first outlet. In a junction box, connect one 12/2 to the black and white of the 12/3, and a second 12/2 to the red and white of the 12/3. If you do that, you can use just two GFCI receptacles, as the first one on each 12/2 line.

I'm wondering is if the shared neutral confuses things with the GFCI
It doesn't merely confuse it. It shoots it in the head. You can never connect anything with a shared neutral to the load side of a GFCI receptacle. The GFCI will trip instantly if the hot current and the neutral current doesn't match exactly. Any time you are drawing power from both the black wire and the red wire, there's no way either of them will ever match the current on the neutral.

This is the primary reason I don't recommend a multiwire circuit for the kitchen countertop receptacles. The small price difference between two runs of 12/2 and one run of 12/3 is more than offset by the extra costs involved. Besides, a multiwire circuit brings a dozen more electrical codes into play, and many people aren't familar with all of them.
 
  #5  
Old 01-27-05, 01:44 PM
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Hi John, thanks for the extra detail, that's exactly what I needed to know. Option 1) sounds easy to wire but difficult to obtain parts, 2) sounds like the one I've seen covered most often, 3) mimics the 2 12/2 arrangement and may be the most straightforward solution.

However, before I rule out options, assuming a multiwire 12/3 were run throughout...

a multiwire circuit brings a dozen more electrical codes into play
Is that type of circuit then likely to be beyond the abilities of a knowledgable and meticulous diy'er to install per code? Is it primarily phase-labelling and handle-tying sort of things, or even beyond that? Would you happen to know of any reference to these requirements (short of reading the entire NEC)? I haven't seen it covered much.

Thanks again
 
  #6  
Old 01-27-05, 01:59 PM
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No, I'm sure you can do it. The two main codes that you need to worry about are:

(1) Pigtail the neutral to any device.
(2) Use a double-pole breaker if the two hot wires both ever connect to the same device. The double-pole breaker is always a good idea anyway.
 
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