How to Figure Out Circuit Numbers By Color

Last updated on February 26th, 2024.

Circuit number colors in a 3 phase panel are really easy to identify once you learn a trick. It’s called the Rule of Six.

Ever heard of the Rule of Six?

It’s surprisingly straightforward. Just divide the circuit number by six, and you’ll know exactly which wire color to use.

And now I’m going to teach you to be a circuit number ninja without using a color coded wiring chart.

How To Identify Circuit Number Colors in a 3 Phase Panel

This method of dividing a circuit number is sometimes easier than carrying around a electrical wiring color code chart. Usually I make up temporary panel schedule on piece of notebook paper before I start pulling in new wires.

Placing colored tape on circuit breakers to identify wiring colors is a common practice. While it’s helpful, mastering the mental calculation will truly set you apart as a skilled apprentice.

A 3 phase panel wiring is A, B, C – left to right- and top to bottom. Circuits are labeled with the odds on the left and the evens on the right.

Normal Wiring for a 120 / 208 V 3 Phase Panel

When using the rule of six you will reference the first six circuits, their phase and color.

The most important thing to remember is this:

If a number divides evenly by 6 then that circuit will be the same phase color as the number 6. If there’s a remainder, use that to determine the wire color.

Example 1:

What color is circuit #24? Divide the number 24 by 6. The answer is 4. Since 6 divided evenly, circuit #24 will be the same color as circuit #6. Using the panel or layout above find what color circuit 6 is. Circuit 6 is BLUE, which means circuit number 24 is BLUE.

Example 2:

What color is circuit #11? Divide the number 11 by 6. The answer is 1 with a remainder of 5. Use the remainder of 5 as your reference and find what color circuit 5 is. Circuit 5 is BLUE, which means circuit 11 is BLUE.

Example 3:

What color is circuit #20? Divide the number 20 by 6. The answer is 3 with a remainder of 2. Use the remainder of 2 as your reference and find what color circuit 2 is. Circuit 2 is BLACK, which means circuit #20 is BLACK.

Starting to get it yet?

Focus on memorizing the colors of the first six circuits in a panel—BLACK, RED, BLUE for circuits 1, 3, 5 and 2, 4, 6, respectively.

This method applies to various voltage color schemes you’ll encounter. For instance, a 277 / 480 volt panel typically uses BROWN, ORANGE, YELLOW for circuits 1, 3, 5, and 2, 4, 6.

If you’re having trouble, try remembering this rhyme – “If it’s divisible by 6 it’s blue, and the one before it too.” This rhyme only work on 3 phase 120/208 volt panels, but you could substitute yellow if you’re working on a 277/480 volt panel.

If you have any questions, feel free to leave a comment. Sharing your insights could greatly assist another apprentice.