Hello. I have a quick junction box question. Is there a limitation to the amount of wires I can safely join in a junction box? If so, what is it and are there regulations to what size box I can use? Thank you.

I would like the have 8 wires (neglecting ground) in one junction box (1 in / 3 out). Can this be done?

Yes, there is a limit to the amount of wires in all junction boxes based on the size wire, a certain amount a cubic inch allowed for each size wire, and the total internal volume of the box in cubic inches.

If using Romex, then all the bare grounds are considered as one wire, and if there is any clamps in the box ,each clamp is counted as one wire, and a device will be counted as one wire.

The typical wire sizes and the volume that needs to be allowed for each wire is as follows:
#14-2.00 cu. in. each
#12-2.25 cu. in. each
#14-2.50 cu. in. each

Assuming you have four #12-2 Romex cables, each with a ground wire, no clamps inside the box, and no device in the box, you need 2.25 CI for each of 9 #12 wires, you will need a box no less than 20.25 CI of volume.

A standard 4 " square box 1.5 " deep has 24 CI of volume.

Shortcut, if you are using a plastic box, look inside for a small chart stamped inside listing the total amount of each wire size allowed in that box, you must deduct for any device that may be installed inside.

Double post