NEC Table 9 Alternating-Current Resistance and Reactance for 600-Volt Cables, 3-Phase, 60 Hz, 75°C (167°F) — Three Single Conductors in Conduit

Table 9 in the National Electrical Code is provides copper and aluminum conductor resistance and reactance data. Units of resistance and reactance are ohms per 1,000 feet. These values are particularly useful for performing voltage drop calculations when the power factor is known. Pay close attention to the notes at the bottom of the table. If the operating conditions deviate from these assumptions, the values need to be corrected. That said, Table 9 is useful for real-world calculations.

Table nomenclature (adjusted slight from the NEC to improve readability online):

XL: Reactance for All Wires
R, Copper: Alternating-Current Resistance for Uncoated Copper Wires
R, Aluminum: Alternating-Current Resistance for Aluminum Wires

NEC Table 9

Wire Size	XL (PVC, Aluminum conduit)	XL (Steel conduit)	R, Copper wire (PVC conduit)	R, Copper wire (Aluminum conduit)	R, Copper wire (Steel conduit)	R, Aluminum wire (PVC conduit)	R, Aluminium wire (Aluminum conduit)	R, Aluminum wire (Steel conduit)
14	0.058	0.073	3.1	3.1	3.1	N/A	N/A	N/A
12	0.054	0.068	2	2	2	3.2	3.2	3.2
10	0.05	0.063	1.2	1.2	1.2	2	2	2
8	0.052	0.065	0.78	0.78	0.78	1.3	1.3	1.3
6	0.051	0.064	0.49	0.49	0.49	0.81	0.81	0.81
4	0.048	0.06	0.31	0.31	0.31	0.51	0.51	0.51
3	0.047	0.059	0.25	0.25	0.25	0.4	0.41	0.4
2	0.045	0.057	0.19	0.2	0.2	0.32	0.32	0.32
1	0.046	0.057	0.15	0.16	0.16	0.25	0.26	0.25
1/0	0.044	0.055	0.12	0.12	0.12	0.2	0.21	0.2
2/0	0.043	0.054	0.1	0.1	0.1	0.16	0.16	0.16
3/0	0.042	0.052	0.077	0.082	0.079	0.13	0.13	0.13
4/0	0.041	0.051	0.062	0.067	0.063	0.1	0.11	0.1
250	0.041	0.052	0.052	0.057	0.054	0.085	0.09	0.086
300	0.041	0.051	0.044	0.049	0.045	0.071	0.076	0.072
350	0.04	0.05	0.038	0.043	0.039	0.061	0.066	0.063
400	0.04	0.049	0.033	0.038	0.035	0.054	0.059	0.055
500	0.039	0.048	0.027	0.032	0.029	0.043	0.048	0.045
600	0.039	0.048	0.023	0.028	0.025	0.036	0.041	0.038
750	0.038	0.048	0.019	0.024	0.021	0.029	0.034	0.031
1000	0.037	0.046	0.015	0.019	0.018	0.023	0.027	0.025

Table 9 Alternating-Current Resistance and Reactance for 600-Volt Cables, 3-Phase, 60 Hz, 75°C (167°F) — Three Single Conductors in Conduit

Table Notes:

These values are based on the following constants: UL-Type RHH wires with Class B stranding, in cradled configuration. Wire conductivities are 100 percent IACS copper and 61 percent IACS aluminum, and aluminum conduit is 45 percent IACS. Capacitive reactance is ignored, since it is negligible at these voltages. These resistance values are valid only at 75°C (167°F) and for the parameters as given, but are representative for 600-volt wire types operating at 60 Hz.

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Source: NFPA 70