Code Change Summary: A new table has been added to Article 250.

Article 250 is the largest article in the NEC^® and yet for years, the article has only had the following two tables:

• Table 250.66 for sizing grounding electrode conductors of alternating-current systems.

• Table 250.122 for sizing equipment grounding conductors.

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:

• Grounding electrode conductors
• Grounded conductors
• Main bonding jumpers
• System bonding jumpers
• Supply-side bonding jumpers

In the 2014 NEC^®, Table 250.66 has only one purpose; sizing the grounding electrode conductor. A new table has been added for everything else besides the grounding electrode conductor, that used to be sized from Table 250.66.

New Table 250.102(C)(1) is for sizing the grounded conductor, main bonding jumper, system bonding jumper, and supply-side bonding jumper for alternating-current systems. Note 1 under the new table contains the 12.5% rule to be used when the largest ungrounded conductor or equivalent area for parallel conductors is over 1100 kcmil copper or 1750 kcmil aluminum.

See image for an example of the new Table.