electrical
I am wondering how conductors are counted for box fill calculations. In the illustration, the box on the left has 4 conductors, hot/neutral coming in and hot/neutral wires carrying power out to the next receptacle. In the box on the right, the wires are pigtailed, yet still two wires bringing power in and two carrying power out to the next thing downstream. But, there is also two short wires connected to the receptacle itself. Does this count as 6 conductors for box fill calculations?
Thanks!
You can get push-in connectors that can take up to 8 wires (assuming you have 14- or 12-gauge wire):
(Though there is some question about whether they're up to code. :)
Please see this answer, for more detail. Basically if you have equipment grounding conductors enter the box, you add 1 fill unit.
In the example you've provided you have 12 if it's a box without internal clamps, and 13 if it has internal clamps.
Current Carrying Conductors
Ungrounded (hot) 4
Grounded (neutral) 3
----------------------------------
7
Equipment Grounding Conductor 1
Clamps (maybe) 1
Devices 2
x2
----------------------------------
4
----------------------------------
Total 13
Best Answer
Box fill is covered in article 314.16 of the NEC. The wires are counted by size and type for example 14 awg wire is 2 cubic inches for each hot , neutral and only counted once for the ground, if you have a pig tail that doesn’t add to the count, if you have 12 awg wire it is 2.25 for each with a mix of 14 & 12 the 1 ground wire counted will be the largest or 2.25. The device or switch/ receptacle counts 2x the cu inches of the largest wire connecting to it so if a 12 gauge wire connects the receptacle takes 4.5 cu inches. If the boxes have clamps those count 1 time also for the largest wire size . That’s the basics the short pigtails and wirenuts are not added in the amount of the fill.