plastic ground protection boards 22 in 100 T load capacity May 22, 2012 · 2’x8′ green ground protection boards 100 T load capacity 2 #12 in nduit Table 3A, 1/2" nduit will take up to 4 #12 THW Example: Load: Motor 3 HP, 1 phase, 230V run ground wire with all motors I = 17A NEC 430=148 Wire Size = 17A = 21.5A .8 NEC 310-16 #10 is next size