Calculating Wires Allowed in Electrical Boxes
I'm trying to determine if any the boxes I've wired have too many wires. I am using all plastic boxes and 12 gauge NM wire with no clamps. This is how I'm calculating the allowed number of insulated wires allowed for the boxes I'm using. Please let me know if my method of calculating allowed insulated wires is correct??
Double Gang Switch Box (34 CUI) --> 34/2.25 = 15 wires allowed. Now subtract 1 wire for the ground & 2 wires for each switch (2*2 = 4) = 10 insulated wires allowed.
Single Gang Switch Box (22 CUI) --> 22/2.25 = 9 wires allowed. Subtract 1 ground - 2 wires for the switch = 6 insulated wires allowed.
Ceiling Box (25 CUI) --> 25/2.25 = 11 wires allowed. Subtract 1 for ground = 10 insulated wires allowed.