Standard blue box from HD single gang. I have 3 #12 going in tie them together and brought out my black, white,and ground. I don’t have my code book , but is this ok ? I didn’t over fill did I? I tucked all wires nice and neat and have room for the receptacle without smashing them in.
Box fill
- Thread starter guschash
- Start date
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LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Before we simply answer you, read through 314.16, and then see if you still have any questions.
- Location
- New Jersey
- Occupation
- Journeyman Electrician (retired)
I don't use them often but don't those boxes have the conductor fill stamped in the box?
- Location
- Tennessee NEC:2017
- Occupation
- Semi-Retired Electrician
These boxes range from 14cu to 23cu and all I've seen are stamped inside.
3 #12 conductors @ 2.25
(assuming) 1 device @ 2x2.25
Do the math!
3 #12 conductors @ 2.25
(assuming) 1 device @ 2x2.25
Do the math!
- Occupation
- Licensed Electrician
Need to know the cubic inch of the box.
I assume "I have 3 #12" means you have three 12-2 romexes.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
9x2.25= 20.25 cu in
With one device this is the cu in needed for 3 - 12/2 nm cables.
With one device this is the cu in needed for 3 - 12/2 nm cables.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
The most popular box of the type mentioned is an 18 cubic inch box. Not enough volume for three 12-2 NM plus a device.
They also have similar box of 20.5 inch volume or even 22.5 inch. They are double or even triple the price of the 18 cubic inch boxes and only those that know when they are needed purchase them.
They also have similar box of 20.5 inch volume or even 22.5 inch. They are double or even triple the price of the 18 cubic inch boxes and only those that know when they are needed purchase them.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Around here the 22.5 is the most popular. That is all we buy unless there is a special circumstance. I don't believe they cost that much more
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Most popular for you to purchase or most popular sold at big box store?
2-3 times cost I mentioned was maybe a bit much, just checked HD website and 18 cubic inch Carlon is $22 per 100 and 22 cubic inch is $34 per 100. Which do you expect average Joe Homeowner to purchase if he doesn't realize the difference or why it may need to be different in some instances?
Craigv
Senior Member
- Location
- Boyertown, PA, USA
In these parts the Carlon B-122A 22 cu in nail-on box is 53 cents sold individually, but way cheaper by the hundred case. I prefer the "heavy" box, which is 76 cents per each and again, far less by the case.
If you're installing a thousand per month, it is real money, but for a small fish like me, I value time and convenience in not stocking extra boxes, and not needing to calculate how many of a given size are needed on a job.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Ok my 2-3 times price maybe wasn't too exaggerating, and I can see them sold much more per piece then per case.
Mustwin351
Senior Member
- Location
- Texas
For three #12 romexes and one device should that not be a total fill of 18 cubic inches?
6 - black and white conductors
1 - equipment grounding conductor
1 - device.
8 * 2.25 = 18 cubic inches
6 - black and white conductors
1 - equipment grounding conductor
1 - device.
8 * 2.25 = 18 cubic inches
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Device counts as two, so 20.25 cu.in.
Mustwin351
Senior Member
- Location
- Texas
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Device used to count as one conductor, it changed to two in maybe 1996 or 1999 I think.
Adamjamma
Senior Member
- Location
- Jamaica and london
Thought it was only device wider than two inches so normal outlet or switch are still one count, not two, like the 50 amp outlet.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
A 50 amp receptacle that requires a 2 gang box counts as 4 conductors
Adamjamma
Senior Member
- Location
- Jamaica and london
Ok..just went and double checked from other day. You are so correct, and I am feeling like I will never get this even though it is basics..lol...
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
I wasn't even aware of that one, and pretty sure it had to be added in one of the last few code cycles.
One complication I see is that most 14-50 receptacles will fit and do have covers for either one or two gang box.
Craigv
Senior Member
- Location
- Boyertown, PA, USA
Here's the 2017 wording:
(4) Device or Equipment Fill. For each yoke or strap containing one or more devices or equipment, a double volume allowance in accordance with Table 314.16(B) shall be made for each yoke or strap based on the largest conductor connected to a device(s) or equipment supported by that yoke or strap. A device or utilization equipment wider than a single 50 mm (2 in.) device box as described in Table 314.16(A) shall have double volume allowances provided for each gang required for mounting.
As I read it, the device would have to be too wide to fit a single gang box in order to require the additional double-volume calculation. If it fits and is listed for single-gang installation but happens to have mounting options for 2-gang, in my opinion there's no requirement to use 4-conductor fill calc. This makes sense, as the device is no larger if it happens to be installed in a 2-gang or larger box.
- Status