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Last Updated: , Created: Tuesday, October 27th, 2009

Getting a good electrical connection with wires.

Have you ever wondered whether you should push an electrical wire through the little connector holes in the back of an electrical outlet, or tighten that wire under the screw head? Keith Dusome is an electrician from Accurate Electrical in Aurora, Ontario who got me to take a couple of outlets apart to see just what happens in both cases.

A Ground Fault Interrupter (GFI) outlet is different from all the other outlets. On this device, placing the wire through the little back hole actually positions it to be clamped into place when you tighten the screw, as you can see in the first photo. Hence, for a GFI, always use the hole in the back AND tighten the screw. Some regular outlets also have this clamping action.

If you look at the second photo you will see how a very small electrical contact is made when you shove the wire through the back hole of an ordinary outlet. It is held in place by a spring type grip, not the screw. This can give you a good connection, or a very poor connection, depending on how straight your wire is and whether it bends to one side or the other. Although this is an approved technique, it is not nearly as safe as properly securing the wire under the screw head. Also, make sure you wrap the wire clockwise around the screw so that the tightening action will draw the screw into the grip rather than shoving it away from under the screw head.

Good wire connections are essential to prevent heat build up and premature failures of outlets, and possible fires. Quality electrical workers will never use those push-in holes in the back of the outlets, except for GFI outlets. They were designed to make life simpler and quicker, but certainly not safer. Thanks Keith.

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Keywords: Wire, Wiring, Electrical, Safety

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