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.
Rule of six you say?
Yes, its actually quite simple. Divide any circuit number by six and you can figure out the color of a wire you need.
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.
It’s easy to stick a piece of colored tape on circuit breaker identify the wiring color for the color scheme that’s in use. This can help keep you on track, but here’s how you can do it mentally and look like an awesome 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.
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.
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.
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?
The idea is to memorize the circuit number color of the first six circuits in a panel. BLACK, RED, BLUE – 1, 3, 5 and 2, 4, 6.
The same goes for any other voltage coloring scheme you may encounter. Normal color wiring for a 277 / 480 volt panel is BROWN, ORANGE, YELLOW – 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 an questions be sure to leave a comment. Your input may help someone another apprentice.