Conductor Sizes

Below is a chart that will assist in sizing conductors and conduits for both electrical distribution and equipment. The data in the chart is based on the 2005 National Electrical Code, Annex "C", Table C.1, Copper Conductors, Type "THHN" at 75º and includes the provisions for wire sizes under 100amps, which are to be rated at 60º per NEC 110.14. This is the most commonly used material and method for wiring of all types of applications in both residential and commercial buildings.

Feeder Sizes for Copper Conductors
NOMINAL AMPERE RATING	CONDUCTORS (3-PHASE, 4-WIRE WITH GROUND)	CONDUIT SIZE
20	(4) #12 AWG, (1) #12 GRND	1/2"
30	(4) #10 AWG, (1) #10 GRND	3/4"
40	(4) #8 AWG, (1) #10 GRND	3/4"
50	(4) #6 AWG, (1) #10 GRND	1"
60	(4) #4 AWG, (1) #10 GRND	1"
70	(4) #4 AWG, (1) #10 GRND	1-1/4"
100	(4) #1 AWG, (1) #6 GRND	1-1/4"
125	(4) #1 AWG, (1) #6 GRND	1-1/2"
150	(4) #1/0 AWG, (1) #6 GRND	2"
175	(4) #2/0 AWG, (1) #6 GRND	2"
200	(4) #3/0 AWG, (1) #6 GRND	2"
225	(4) #4/0 AWG, (1) #4 GRND	2-1/2"
250	(4) #250 KCMIL, (1) #4 GRND	2-1/2"
300	(4) #350 KCMIL, (1) #4 GRND	3"
350	(4) #500 KCMIL, (1) #3 GRND	3"
400	(4) #500 KCMIL, (1) #3 GRND	3"
500	(4) #250 KCMIL, (1) #2 GRND X 2 PARALLEL SETS	3" X 2
600	(4) #350 KCMIL, (1) #1 GRND X 2 PARALLEL SETS	3" X 2
800	(4) #500 KCMIL, (1) #1/0 GRND X 2 PARALLEL SETS	3" X 2
1000	(4) #400 KCMIL, (1) #2/0 GRND X 3 PARALLEL SETS	3" X 3
1200	(4) #600 KCMIL, (1) #3/0 GRND X 3 PARALLEL SETS	4" X 3
1600	(4) #600 KCMIL, (1) #3/0 GRND X 4 PARALLEL SETS	4" X 4

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Conductor Sizes

Feeder Sizes for Copper Conductors