26 mm 2 (10 AWG) ground wire must be used, and in all other markets a 6 mm 2 must be used. On the US market, a 5. NEC specifies that the number of wires, including the ground wires, should not. When you have more than one circuit in a box and using metal clad cable or romex do you tie all the equipment grounds together. If you tie both circuits together and bond the box you can have a lot of equipment grounding. Learn how to properly size ground wires according to NEC requirements. Proper grounding is one of the most critical aspects of electrical. Part (1) of Section 370-16 (a) describes in detail the method of counting wires, as well as clamps, fittings, or devices (i., switches, receptacles, combination devices) - by establishing an equivalent conductor-value for each. These values are added together to get a total number of conductors. My question is if it is acceptable to tie all ground wires together in the attic junction box and just run 1 pigtailed ground wire to the switch box and then pigtail 6 ground wires off that 1 ground to the device switches.