Running too many wires through an access hole in a junction or switch box can cause damage to the wires' insulation resulting in short circuits and fires. Generally, a 7/8-inch hole is designed to accommodate three wires. In this article, we will explore the safety considerations when drilling. To help, I talked to two experienced electricians to walk through these top 15 electrical mistakes to avoid. Below, find out what to look for, and how to fix what you find. Electricians always carry non-contact voltage testers with them, and you should have one, too. Today, I tried to run the 4/0-4/0-2/0 cable from the meter box. Tightly stuffed junction boxes and sloppy splicing can turn an everyday wiring job into a hidden fire risk. Many homeowners, when adding outlets or lights, will pack a box until it's bursting or twist wires together with only a hint of tape—skipping code required steps that are easy to overlook.
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