I purchased 2 Carlin 2-gang old work box with max cubic in fill limit of 25. These are being installed in a garage so each receptacle is gfci. I have wired them in parallel so there is a pigtail in each box for ground , neutral, and hot and a respective conductor for each receptacle. I wanted each gfci to be independent of the other since there is a fridge on one and didn’t want that to trip from the other outlets so ended up applying this logic to all of them. However having installing them I realize the gfci are HUGE and take up the majority of the box. In fact having two gfci in one box with the three pigtails using ideal protwist nuts, one in coming nm 14/2 Romex cable supplying the load results in me having to use the screw in force of the outlets to push it in.
So my question does the gfci require any addition volume for box fill (based on nec AND/OR some unofficial electrician rule of thumb adjustment). I ask this because I am worried with the fact I needed to rely on the force of screwing in to actually get the receptacles and wires to go in the outlet box correctly (might sound dumb but this is the first time I’ve encountered that issue)
Best Answer
A GFCI only requires the same fill as any other device. In your case with 14-2 one cable in one cable out and the device 4 current carrying conductors 1 ground ,x 2 device , clamp. 14 awg =2 so 2 x 8 or 16cu inch. 2 devices ? 20 cu inches?
There should be plenty of room, if you get excessive with your wire length that will quickly gobble up room, if your wire or pig tails are longer than 6” trim them back the next thing would be to make sure to make sure your wires are packed tightly in the box I have had people that try to put a foot long end and long pigtails in boxes and can’t get them in the box so length and arrangement in the box make a difference. Although GFCI devises are bulkier than normal devices they require the same device fill as other devices unless marked by the oem and I have not seen that.