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MrBill_DIY 10-04-2008 09:59 PM

Bare Ground Wires
I have a very basic question about ground wires. I have two how-two books on electricity, and in the pictures one book shows ground wires as bare and the other book shows them with green insulation. Why is it okay to use bare ground wires inside an electrical box instead of insulated ones? I would think that bare ground wires could rub up against an electrical contact. And what would happen if a ground wire did touch an electrical contact?

InPhase277 10-04-2008 10:28 PM

A short circuit would develop if a ground wire touches a live contact. I'm not exactly sure of the history of why wire manufacturers began making cables with a bare ground. I imagine it may be that they figured the boxes they were going in were all metal (at that time), and grounded, so it didn't matter if the ground was bare also. I'm sure it also costs a little more to insulate the ground. I would like to see that happen someday. But careful electricians tuck their wires neatly into the boxes so that no contact occurs.

At any rate, carelessness can cause a short with or without insulated grounds.

Jim Port 10-04-2008 10:30 PM

If the bare is properly connected at the panel and comes in contact with an energized part it would trip the breaker.

Billy_Bob 10-04-2008 10:41 PM

Basically the metal cases on *everything* electrical should be grounded, so no problem with a bare ground wire touching any metal case/box. Also it is less expensive to manufacture the wire.

Now if a bare ground wire were to contact a "hot" conductor, then this would trip the breaker*. Or if a "hot" wire were to contact a bare ground wire, then this would trip the breaker.

The best part of all this is if a hot wire (say in an appliance like a range) were to touch the metal case of the appliance, then this would trip the breaker. This is a neat feature about grounding. It will either trip the breaker or at least keep the "short" at "ground potential" so people are protected from being electrocuted.

As to wiring outlets, I like to connect/bend the ground wires so they will go to the back of the box when installing the outlet. Keep them away from the front sides of the box.

As for insulated green ground wires, you will see this on appliances with stranded wire cords where everything can be moved, dropped, twisted, etc. In this case you wouldn't want a ground wire to go flying around inside the appliance and possibly contacting a hot connection.

*Assuming everything is wired to modern code.

MrBill_DIY 10-05-2008 07:05 PM

Thanks, that's good information. I've been trying to push the bare ground wires to the back of the electrical box as you said, to keep them away from the contacts on the receptacles.

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