Calculating the length of DC wires

Use these variable definitions

To calculate the maximum combined length of the positive and negative wires between the DC source and DC power supplies, use the following variable definitions:

How to calculate the length

The following two examples show how to calculate the maximum combined length of the positive and negative wires that connect the DC power supply to the DC source.

Example 1

This example uses the following given values.

For example, if you have a 12 gauge wire, solid strand, at room temperature, use the following calculation.

AWG	Strand	DC resistance1 [/ft.]		Total cable length2 [ft]
AWG	Strand	25º C	75º C	25º C	75º C
12	Solid	.0017	.0020	75	64
12	7/20	.0015	.0018	85	71
12	19/25	.0017	.0020	75	64
12	65/30	.0018	.0022	71	58
12	165/34	.0016	.0019	80	67

1 Data from Alpha Wire, wire manufacturer

2 Combined positive and negative run

Example 2

This example uses the following given values.

For example, if you have a solid strand 12 gauge wire at room temperature, use the following calculation.

AWG	Strand	DC resistance1 [/ft.]		Total cable length2 [ft]
AWG	Strand	25º C	75º C	25º C	75º C
12	Solid	.0017	.0020	136	116
12	7/20	.0015	.0018	155	129
12	19/25	.0017	.0020	136	116
12	65/30	.0018	.0022	129	105
12	165/34	.0016	.0019	145	122

1 Data from Alpha Wire, wire manufacturer

2 Combined positive and negative run

About using other wire sizes

If you need a longer run for your combined positive and negative DC wires, choose a wire with a lower resistance and calculate the total cable length. For example, a solid #10 AWG has a lower DC resistance than a solid #12 AWG.