Another normal wire association issue is the point at which you discover at least two wires held under a solitary screw terminal on a switch or outlet. This is a reasonable indication of novice work and a particular fire risk. It is reasonable to have a solitary wire under every one of the two screw terminals in favor of an outlet or switch, yet it is a code infringement to have two wires wedged under a solitary screw. This is regularly observed when two exposed copper establishing wires are found under the establishing screw on the outlet or switch, however you likewise may sporadically discover hot wires or unbiased wires associated with a solitary screw terminal.
Two or More Wires Under One Screw Terminal: Is it Safe?
If you are looking at an outlet or switch and wondering if you can loop two wires around a single screw terminal, the short answer is almost always no. This practice, often called “double-tapping,” is a common DIY mistake that can lead to electrical fires, melted devices, and code violations.
The Standard Rule: One Wire, One Screw
For standard residential outlets and switches, screw terminals are designed to hold only one conductor. When you place two wires under one screw, the screw cannot apply even pressure to both. This creates a loose connection, which leads to arcing a condition where electricity “jumps” across gaps, generating intense heat.
The Safety Hazards of Double-Tapping
- Fire Risk: Arcing can ignite surrounding insulation or plastic components.
- Circuit Interruption: Loose wires can slip out, causing half of your room’s outlets to stop working.
- Melted Terminals: Over time, the heat from a poor connection will degrade the integrity of the receptacle.
Step by step instructions to Fix
By and by, this fix includes first closing off the power. At that point, the two culpable wires are expelled from their screw terminal. Cut a 6-inch ponytail wire of indistinguishable shading from the two wires (utilize a green braid on the off chance that you are joining two exposed copper establishing wires). Strip 3/4 inch of protection from each finish of the ponytail, at that point go along with one end to the two wires you simply detached, utilizing a wire connector (wire nut). Presently, join the free end of the ponytail wire to the screw terminal that once held the two wires.
You have basically made a scaffold, or pathway, that interfaces the two wires to the ideal screw terminal on the outlet or switch.
Terminals Rated for Two Conductors
There is one scenario where two wires are allowed: Pressure Plate Terminals.
Some commercial-grade or high-end residential receptacles feature a metal pressure plate behind the screw. If the device is UL-listed and specifically designed with “back-wire” (not “back-stab”) holes that tighten via the side screw, it may be rated for two conductors.
Pro Tip: Look at the back of the device. If there are two distinct channels under a single metal plate that clamps down when you tighten the screw, it is likely rated for two wires. If you have to “loop” the wire around the screw, it is only rated for one.
How to Properly Connect Multiple Wires (Pigtailing)
If you need to connect two or more wires to a single terminal, the correct method is to use a pigtail:
- Take the wires you need to connect and a short 6-inch “pigtail” wire of the same gauge.
- Join them all together using a wire nut or a lever-style connector (like a Wago).
- Connect the single remaining end of the pigtail to the outlet screw.
This ensures all wires are securely bonded while maintaining a single, solid connection to the device.
Why Chicago Homeowners Should Be Careful
Electrical codes in the Chicago area are among the strictest in the country. What might pass for a DIY “quick fix” elsewhere could be a major code violation here, especially in buildings that require full conduit systems.
Note: Make sure the pigtail wire is the same wire gauge as the circuit wires. A 15-amp circuit normally used 14-gauge wire; a 20-amp circuit uses 12-gauge wire.
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STS Electric provides Electrical services across Chicago neighborhoods and surrounding Cook County communities. Our licensed electricians understand local building requirements and deliver dependable service across residential, commercial, and industrial projects.
