[ssmith5427]

I am running 2, 100 amp disconnects off a 200 amp disconnect. The run is 100 feet long. I am told that I can use #1 copper for the power lines. What size should the neutral and ground wires be for this run?

[InfoJunkie4Life]

I believe the neutral is required to remain the same size, however the grounding wire may actually be allowed to be smaller. I'm not sure of the exact amount, but I believe it can be found in NEC #250-66.

I don't have a NEC book available, and I couldn't find the table online...

Good Luck

[tkrussell]

The NEC is available on line as read only:

NFPA 70: National Electrical Code®

Table 250.66 is for the grounding electrode conductor, which is the "ground" wire connected to the water main and/or ground rod(s), not the "neutral", AKA grounded conductor of a feeder.

The neutral of a feeder can only be reduced 70% of the ungrounded (live)conductors IF the unbalanced current is calculated.Not worth the trouble, use a #1 for both live and neutral conductors.

The "ground" of the feeder to the panel(s) is called the equipment grounding conductor, and is sized according to Table 250.122, that refers to the ampacity of the overcurrent protection device, AKA circuit breaker.

For a 100 amp feeder, a #8 copper with green insulation, is the minimum size allowed.

[InfoJunkie4Life]

I know the difference between "Grounded" and "Grounding" and I was sure the grounding line could be reduced in size, but the only reference I found online to how much 250-66. Thanks for the clarity... I've seldom followed codes, it just seemed illogical to me to use a reduced neutral. Generally I use the same gauge wire for Neutral, Live, and Ground.

[tkrussell]

Info, perhaps you do know, but the poster certainly does not, and that was what I was trying to address.

Attempting to illustrate that the term "ground" is widely misunderstood, or misused, and the only way I know how to discuss this is using the proper terms.