Replacing electrical box, what size to use?


Adding a wallmounted TV in my basement, I wanted to run power from an existing outlet 3' below where the TV will be. I have the holes cut and the Romex run, but the original receptacle is fed by AC cable into a metal box (obviously). 4 conductors total, with a receptacle and one clamp. If I feed power to the new TV outlet, that will be another 2 conductors and another clamp.
So basically what size box is now recommended (required?), for 6 conductors, 2 clamps, and a receptacle? I found something on Racos site that pointed at 22.5 cu in required, but I wasnt absolutely sure about their chart
Thanks in advance! -Chris
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Without a code book in hand I can't be accurate, but since you're going to open the wall to replace the existing box, just get a deep bang on 1900 box, and you're covered

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By deep bang on 1900 box he means a 2-1/8" deep x 4" square steel box with nail-on bracket. Add a plaster ring sized for the drywall or other wall finish you have, and you will have plenty of capacity.
Glenn http://www.goalelectrical.com A forum that speaks YOUR language.
RBM (remove this) wrote:

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snipped-for-privacy@gmail.com wrote:

c:
It's a requirement, yes. The NEC has a nice chart of standard steel box volumes and the rules used. Without knowing what wire size you are dealing with, I'll just try both.
The Raco box info is quite correct and very handy. It comes as a shock, though, when you first understand the box fill rules, and realize that most steel boxes stocked by home improvement stores are nearly useless for all but very basic situations. Note that Raco does not show all their boxes on the chart; just the ones they consider most
useful or popular. You can, however, look up other boxes in their catalog (like the common 2 1/4" deep old-work device box that home centers looove to sell)
**/2 Romex in - 2 conductor allowances **/2 Romex out - 2 " " All grounds - 1 " " (all grounds, however many, always count as 1) All clamps - 1 " " (Clamps count as one) One device - 2 " " (Count two for every yoke-mounted device)
Pigtails or other conductors which start in the box and don't leave it need not be counted.
Total allowances: 8 (Note...if this is old Romex with no ground then you may reduce the total to 7, but you must then use a nonmetallic box)
Conductor volume allowance for 14 AWG = 2.00; for 12 AWG = 2.25
Total volume required:
14/2 in & out: 8*2 = 16 cu in 12/2 in & out: 8*2.25 = 20 cu in
Your new end-of-run outlet for the TV just has two conductors, a device, grounds, and probably a clamp, for a total of 6 cu in. You will need 12 cu in for 14/2 w/ground; 13.5 for 12/2 w/gnd.
A 4" square, 1 1/2" deep box will do. Screw it to the basement wall and add a mud ring...if the wall is too shallow for this, you may be stuck with surface wiring, or using a domed cover and letting the box project from the wall, but this last solution has that ad hoc industrial look that the little woman often fails to appreciate. :) The minimum depth you will need for a recessed outlet is a bit over 1 1/2", if you use a flat mud ring, and put a washer or two behind the box on each screw to give some space between it and the wall for the ground screw.
As usual, remember to pull a permit and submit the work for inspection by the AHJ. I am not an electrician, and I can't really see what you situation is from here.
Cordially yours: G P
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I already ripped out the old box :) The situation at hand pretty much dictates I need a larger box (I forgot to mention there is already 4 conductors in the box.......1 AC in, 1 AC out to the rest of the basement). I need to pigtail to the new Romex off one set of AC, so a standard outlet box will be way too small. If Racos sizing is correct, I need a 4" box or a 4 1/16" box. I actually was surprised, but not so surprised at the same time. I realize the need for the extra space (Ive taken apart some wiring already existing in teh house, and half the time I wonder how they even fit it all in in the first place), and since this is my basement, I have no problem getting a bigger box to make the wiring easier for myself (it will look "off" because the rest of the outlets are duplex, but hey its just a basement). FWIW, Im using 12/2 wire.
As far as the TV end, I have a pullout wallmount, so I dont have to have a recessed outlet. Because of that, I just put in a Carlon old-work zip box (Ill tie the Romex ground to the metal box Im replacing), and Ill add a Leviton hospital grade outlet with TSS. I may make a shorter power cable to the TV, in which case Ill use a "flat" 3-prong plug to the outlet, to reduce the protrusion even further.
Thanks again! -Chris
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On 11 Nov 2006 06:38:43 -0800, snipped-for-privacy@gmail.com wrote:

I know someone who had that problem this week. He used a 2-gang box and put a receptacle in there to make it look right.

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Yep, exactly what I did. Got an "old work" box (enough of the drywall was ripped out from removing the previous box that I could get my air palm-nailer to the stud) and a centered single device mud-ring cover, so I can get away with one receptacle and it will look the same.
One question, however.........since its a 2-gang box, Im assuming you cant cover the box cover screws with drywall? So Ill either need a 2-gang wide wallplate with a center opening, or Ill actually have to put 2 receptacles in teh box. I coudlnt quickly find a 2 gang wide wallplate for a single device, but Im hoping they are out there.
-Chris
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Oops. I meant new work. But still have the dilemma about how to cover it with a wallplate.
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snipped-for-privacy@gmail.com wrote:

c:
As the name 'mud ring' implies, you just bury the whole thing in plaster, leaving the raised opening for access. This unfortunately does bury the mud ring-to-box screws, but then you need to do minor excavation to free most boxes from a plaster wall. If the small size of the access hole worries you, you can use a 2-gang mud ring and buy a 2-gang cover with one blank spot.
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On 13 Nov 2006 06:59:20 -0800, snipped-for-privacy@gmail.com wrote:

I have wanted those before, and could use a source.

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i would go with a 4s deep and put a 1 gang plate on it http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&itemv01512492&categoryB886

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Yep, exactly what I did! Got a 4" square, 2.125" deep box from HD (depth is probably overkill but it fit so Im not gonna argue), and managed to find a double gang, single device "mudring" cover. That will at least get everything up and running. Still need to locate a dual gang wall plate with only one device opening in the center. But again at least I can get everything up and running for now.
Thanks everyone.
-Chris
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On 10 Nov 2006 17:35:34 -0800, snipped-for-privacy@gmail.com wrote:

If you are good at it, you should be able to fit the new wires in the original box. You connect the new wires to the spare screws on the original outlet. Use a modern outlet in that box too. Most are thinner than the old ones. If you dont want to rip out the old box, get a "Wiremold" brand, box extender. The outlet will be outside the box and stick out of the wall abourt an inch.
Mark
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