NEC questions

mudwormSeptember 27, 2011

Sorry I don't have easy access to the recent NEC, and I find it hard to search for answers in whatever excerpt of the code posted online -- they speak a different language!

I hope someone with experience may know the answers off the top of his head. Could that be you?

1. Can I hide electrical wires under crown molding? This is to retro fit more lights into a room without opening up the ceiling.

2. The previous owner left a metal conduit in the crawl space that runs three 10 wire gauge wires inside from the service panel to a junction box, but it terminates there. Can I run a 10-3 NM from that junction box (with the ground attached to the metal junction box) into my kitchen for a 30A/240V oven? If yes, I suppose at the service panel, I need to connect the conduit to the ground bus too, right?

3. I will have a split duplex receptacle to serve dishwasher and instant hot, each on its own dedicated circuit. Can I run a 12-3 NM and share neutral?

4. Has 2011 NEC disallowed MWBC?

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Ron Natalie

The NEC is available online for a free trial at necplus.org. You can find paper copies at many public libraries (perhaps in the reference section).

1. You can put wires that are approved for concealed use (such as NM) behind crown molding. Be sure to guard against physical damage.

2. You can use the metal conduit as the ground and extend the circuit with NM. You must use an appropriate NM fitting at the box. Hopefully, the conduit is already installed with listed connectors/couplers that provide the ground path.

3. You could do this, but you'd need to make sure that neither unit requires a GFCI by it's manufacturer. If so you can put a 2-pole GFCI with load neutral in and run the split circuit.

4. No, MWBC is still allowed, however given that just about everything that doesn't require a GFCI by code now requires AFCI, the ability to actually use a MWBC is severely limited.

    Bookmark   September 28, 2011 at 6:16AM
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mudworm

Hi ronnatalie, thanks very much for sharing the information and your knowledge! It appears that the access to necplus.org is subscription based at $125/year and the free trial is available for only one day. I'd better save that chance for later when I have accumulated questions that I must consult NEC for. For example, I wonder what the specific code requirements are for wire protection under crown molding.

    Bookmark   September 28, 2011 at 8:40PM
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Ron Natalie

There isn't anything specific. I'd mount it far enough away from anyplace a finish nail could go installing the moulding as I could.

    Bookmark   September 29, 2011 at 9:29AM
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mudworm

Great. Thank you! That will make it a little easier when I wire a room without opening its ceiling.

    Bookmark   September 29, 2011 at 5:48PM
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mudworm

A few more questions popped up. Hoping someone can help me. TIA!

1. We have an existing 20Amp circuit that supplies two receptacles above countertop in the kitchen as well as three receptacles in the living room. I will make sure the two receptacles in the kitchen are GFCI protected, but I assume in order to meet the 2011 NEC code (without changing the wiring of the circuit), we need to use an AFCI breaker for this circuit. Is that correct?

2. I also plan on wiring a dedicated 20Amp circuit for the entertainment center, and another one for all the computer equipments in the desk area (both are in the general living room area). I will be using a surge protector/APC unit on each circuit to protect the delicate equipments. I'll still need to use AFCI breakers for these two circuits, right? And will they not interfere with the APC/surge protector?

3. AFCI breakers are not required for any light only circuits (no outlets), correct?

4. Neither AFCI breaker nor GFCI receptacle is required for the dedicated appliance circuits (e.g. DW, range hood, fridge) regardless whether they are hardwired or plugged in, correct?

    Bookmark   October 10, 2011 at 4:22PM
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mudworm

Sorry, one more question:
5. I will be adding a new 20amp small appliances circuit in the kitchen. I plan on using only a GFCI receptacle for the first one, and wire the rest down the stream from its LOAD SIDE terminals. That way, I don't need GFCI receptacles everywhere. This practice is not disallowed in 2011 NEC, correct?

    Bookmark   October 10, 2011 at 4:36PM
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