The size of a typical earthing jumper for a cable tray ranges from 6 AWG to 2 AWG. 120 (A)] and the correct methods. 45 for solar. Even though Table 250. 66 is titled Grounding Electrode Conductor for Alternating-Current Systems, for many code cycles, the following items in Article 250 were all sized from the table: In the 2014 NEC ®, Table 250. 66 has only one purpose; sizing the grounding electrode conductor. A connection resistance above 0. Properly bonding the supply side of service and the load side of overcurrent devices is vital in a. Size conductors installed in cable tray with NEC 392, NEC 310. 16, tray fill, ampacity adjustment, voltage-drop checks, grounding, and IEC design cross-checks.