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Old 07-14-2011, 05:04 AM   #1
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Adding New 20A Circuit - Wiring Check


Looking to add a new circuit. It will be within only one room. I plan on having 6 pendant lights on a dimmer and 3 unswitched outlets. I calculate typical load to be less than 600 watts, but want some fudge factor for future-proofing so I'm shooting for a 20A install on #12-2 Romex.

I was thinking that I'd connect to the first outlet, then branch out one side to dimmer switch and the other side to the two remaining outlets. I'd continue to the other two outlets using only the back-holes and screws. From the dimmer switch, I'd pigtail the pendants together with wire nuts. The only hard part is getting from the outlets that I could only access from the crawl space to the pendants that I could only access from the attic (I think I have the cable bits and patience to fish it).

Since the dimmer is single pole, the neutral should bypass it entirely and continue to the first pendant pigtail, right?

Without a second dimmer controlling the same pendants, there's no need for a 3-wire setup, right?

Other than the slight additional cost, is there any reason I shouldn't upgrade to a 30A breaker with #10-2?

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Old 07-14-2011, 05:25 AM   #2
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Adding New 20A Circuit - Wiring Check


General purpose circuits can’t be more than 20 amps, so no, don’t use 10/2 with a 30A.

From what you described, your typical load of 600 watts=5 amps. 14/2 on a 15A circuit would be fine.

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Old 07-14-2011, 05:58 AM   #3
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Adding New 20A Circuit - Wiring Check


Makes sense. I'll be sure to stay under 30A. I have a bit of 12-2 laying around, but I'll consider grabbing some 14-2.

Does this look correct? The circles are wire nuts.
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Old 07-14-2011, 06:25 AM   #4
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Adding New 20A Circuit - Wiring Check


Looks good, but make sure that the boxes are large enough for the number of wires and devices.
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Old 07-14-2011, 06:45 AM   #5
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Adding New 20A Circuit - Wiring Check


I'd probably run a 15A circuit - 14g wire is much easier to work with.
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Old 07-14-2011, 06:54 AM   #6
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Adding New 20A Circuit - Wiring Check


About that... I'm having trouble finding metal boxes large enough to meet NEC requirements. If I went 12 AWG:

~~~~~ Outlet Box ~~~~~
12/2 from panel 2 - 12 AWG
12/2 to outlet 2 - 12 AWG
12/2 to dimmer 2 - 12 AWG
Cable Clamps 1 - 12 AWG
Receptacle 2 - 12 AWG
Ground Wires 1 - 12 AWG
--------------- -----------
Total 10 - 12 AWG
10 conductors x 2.25 cu in/conductor = 22.5 cu in minimum box

I can't find any 1-gangs nearly that large. If I go 14 AWG, I'm still looking at 20 cu in, and I'm not seeing any boxes above 16 cu in or so.

Adding another receptacle to the same box adds 4 conductors, putting a 12 AWG minimum at 31.5 cu in or a 14 AWG minimum at 28 cu in, both doable (but I have to use a 42 cu in box for the 12 AWG setup).

Am I calculating this correctly? What is my recourse?
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Old 07-14-2011, 07:46 AM   #7
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Adding New 20A Circuit - Wiring Check


Use a 2 gang box with a single gang plaster ring or re-plan your wiring so you only have 2 cables in a box.

Ex: Panel to R(ecptacle)1 to R2 to R3 to switch to L(ight)1 to L2 to L3, etc.

Only 2 cables per box.

In your first post you mentioned using the back-holes on the receptacles. Do not use them, they have a bad reputation for good reasons. Use the screws or pig-tail the in and out cable.

I assume this is living space so you will need to supply with an AFCI circuit breaker.
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Old 07-14-2011, 08:21 AM   #8
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Adding New 20A Circuit - Wiring Check


http://www.alliedmoulded.com/index.c.../categoryid/54

22.5 cubic inch - this is the brand my local supply house sells, seem pretty god quality.
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Old 07-14-2011, 09:40 AM   #9
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Adding New 20A Circuit - Wiring Check


Indeed, living space. Can't think of any non-living space where pendants would look even remotely good. Also did plan on using an AFCI. In fact, I'm not aware of any way to do it. That's probably a good thing. :D

Wasn't aware of the problems with backstabs until I just researched them. Though the three outlets that I'd pulled, I've switched back to hooks on just because I hate having to carry a suitable tool for releasing the springs.

Edit: Definitely will stretch out the circuit to attach the switch after the last outlet. Unless I decide to break the pendants into two dimmers of three each, that should solve the problem with wall box space.

Last edited by Thadius856; 07-14-2011 at 09:42 AM.
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Old 07-19-2011, 03:25 AM   #10
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Adding New 20A Circuit - Wiring Check


Just a little update for those curious...

The outlet layout I wanted might not work. Crawled underneath and realized that where I wanted them is the old perimeter footing for the original exterior wall. I have a 50-50 chance of drilling in to hit the (double?) bottom plate/4x8 floor joists or concrete. Added a 4x4 junction box in the attic in the meantime so I can branch from there, and so I'd have somewhere to run the lighting wires to while I decide how I want to procede with the rest of the circuit.

Spent most of my weekend crawling around in my unfinished attic. Noticed that the catwalk above the room I was working on was resting on four old 2x4s - one intact, two snapped in half and one not even touching the catwalk. Previous owner thought it would be okay to just float it there, not security it to anything and holding it together with un-nailed twisted wire ties. Not cool. Now secured.

Was at Lowes grabbing something, saw a mini pendant I liked marked down from $41 to under $10, so I picked up the last 5 they had and modified my layout slightly. Measured, marked, drilled exploratory holes, expanded to a 1" bore, moved fiberglass bats and blown cellulose, traced the ceiling boxes and cut them out. Bridged the joists with ~14" sections of pine 2x4 and 3" decking screws. Secured the boxes with 2" decking screws from underneath. Attached pig tails.

Ran 14-2 from the junction box to the lights, in two seperate circuits (wanted two branches for two dimmers). Assembled pendants to their shortest length (15"), trimmed the wire, attached the brackets, connected to circuit, tightened clamps, and completed attaching to ceiling boxes. Moved bats and cellulose back into place.


One question... I connected the each pendant's ground wire to the circuit's ground. But I didn't ground the ceiling boxes themselves. Do I need to go back, add an extra ground to the wire nuts, and clip it to the ceiling box?
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Old 07-19-2011, 07:56 AM   #11
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Adding New 20A Circuit - Wiring Check


Any metal box should have been bonded to the circuit grounding conductor. All the grounds need to be connected together.
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Old 07-19-2011, 09:09 AM   #12
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Adding New 20A Circuit - Wiring Check


That's what I had figured. No harm done I suppose, since the circuit hasn't been energized yet. It's an easy enough fix.
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Old 07-19-2011, 11:28 AM   #13
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Adding New 20A Circuit - Wiring Check


You mentioned "clipping" the ground wire to the box. You should be aware that there are requirements for how the ground wire gets conencted to the metal box, and clipping doesn't meet them - neither does sheet metal screws, generally speaking.

Typically metal junction boxes will have a bump with a threaded hole for attachment of the ground wire, somebody else can probably fill in the specifics better than I about what ground screw requirements are.
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Old 07-19-2011, 03:55 PM   #14
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Adding New 20A Circuit - Wiring Check


These clips are approved for bonding a metal box. Screws are preferred, but sometimes just won't work.
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Old 07-19-2011, 11:44 PM   #15
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Adding New 20A Circuit - Wiring Check


Those were the clips I was going to use. Didn't see your post until after I got back from the Big Box in the next city over. Just picked up a 100-sack of grounding screws, and I'm fairly confident that all of my boxes will accomodate them just fine.

My plans for this circuit have expanded a bit. It now contains five pendant lights on two dimmers, 4 outlet boxes on a switch, 4 always-hot outlet boxes, and a two-bulb ceiling dome light on a switch.

As such, I've expanded to two 4x4x2.5 junction boxes to handle all of the connections.

I'm still expecting to only pull 700 watts at most for normal use... obviously more if somebody were to plug in a vacuum or something (no carpet in the entire house), but I still feel comfortable on a 15A circuit.

Picked up a stack of wire labels while I was in town. Plan on drawing my wiring diagram in AutoCAD after I'm done, and number the outlets on the blueprints.

Do I need to use conduit where I enter the panel from above or below, and if so, what length does it need to cover?

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