Why is bundled wiring in an electric panel a defect?
Tuesday, July 10, 2018
Neat and organized wiring is one of the ways you can tell that an electric panel was wired by a professional electrician. Wires from breakers on the right side of the panel exit the box on the same side. They don’t cross over the service cables or run around the bottom. This requires planning and careful execution, and the completed work sometimes resembles a wiring diagram, with each wire turning at a right angle next to the breaker before it heads up or down and out of the box.
A good electrician is justifiably proud of a well-organized panel. But bundling the wires together with zip-ties to further enhance the organization of the panel, like in the photo above, is a step too far. Both the wiring and breakers in a panel generate heat and air space around the components is needed for heat dissipation. When the wires are bundled, heat generated by the inner wires is trapped by the surrounding ones. Also, each wire connected to a breaker helps to conduct heat away from the breaker, but this is nullified if the wire runs into a bundle just an inch away from the circuit breaker terminal.
The National Electric Code does not directly ban bundling in a panel but does require adjusting wire size (derating) for bundled wiring 24-inches or more in length as a way to avoid overheating. Because many wires converge and heat is concentrated in an electric panel, even if the length does not exceed 24-inches, bundling is still the wrong thing to do.
Also, see our blog post Why do some wires in an electric panel have tape wrapped around them near their connections?
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