your egc must be per code:
250-2. General Requirements for Grounding
(d) Performance of Fault Current Path. The fault current path shall be permanent and electrically continuous, shall be capable of safely carrying the maximum fault likely to be imposed on it, and shall have sufficiently low impedance to facilitate the operation of overcurrent devices under fault conditions.
The earth shall not be used as the sole equipment grounding conductor or fault current path.
250-122. Size of Equipment Grounding Conductors
(c) Multiple Circuits. Where a single equipment grounding conductor is run with multiple circuits in the same raceway or cable, it shall be sized for the largest overcurrent device protecting conductors in the raceway or cable.
Table 250-122. Minimum Size Equipment Grounding Conductors for Grounding Raceway and Equipment
Rating or Setting of Automatic Overcurrent Device in Circuit Ahead of Equipment, Conduit, etc., Not Exceeding (Amperes)
Size (AWG or kcmil)
Copper Aluminum or Copper-Clad Aluminum*
15 14 12
20 12 10
30 10 8
40 10 8
60 10 8
100 8 6
200 6 4
300 4 2
400 3 1
500 2 1/0
600 1 2/0
800 1/0 3/0
1000 2/0 4/0
1200 3/0 250
1600 4/0 350
2000 250 400
2500 350 600
3000 400 600
4000 500 800
5000 700 1200
6000 800 1200
remember this egc has to be sized for voltage drop so keep it the same size as your largest wire
