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I remember our home inspector commenting that all but two of the outlets in our 1943 home appeared to be correctly grounded. I was surprised and somewhat skeptical, but haven't really thought about it much.
Well I replaced all of the outlets upstairs which is apparently all on a separate circuit that was installed later from a new subpanel in the basement. All of these were in fact properly grounded.
Now I'm replacing the outlets in a bedroom downstairs. The three outlets in this room are all three prong. I pulled them out to inspect the wiring and wasn't too surprised at what I found. Only one incoming wire is Romex and I don't know for sure where this comes from or goes to. I suspect nothing, but will confirm. Anyway, each outlet has a small piece of wire connecting a terminal on the neutral side of the outlet to the ground screw. Would this have the effect of "faking" a good ground?
Yes it will, and in many circumstances it is good enough. Many people think that doing this makes the electrical outlet the same as a modern three-wire system.
However, electrically they are NOT the same, because the ground and neutral are being carried on the same wire. The difference is both subtle and profound - and very important.
When nothing is malfunctioning, functionally there will be no difference. When a malfunction appears, then this is where the difference becomes critical.
The three wire system provides an additional margin of safety against a neutral fault, and a neutral fault is the dangerous one which can cause lethal shocks. If the neutral line opens for whatever reason, in a two wire system the device plugged in can charge up and cause electrical shocks because the hot wire is still connected. In a three wire system, the current that would ordinarily charge the device is shunted to ground through the separate third wire. When you wire neutral and ground together, you completely lose this protection against a neutral fault, yet an ordinary outlet tester will report the outlet as being properly grounded.
This separate ground also becomes significant when there is a highly inductive load (refrigerator) on a circuit along with electronics. Without going through all the hairy details, separating ground and neutral will cause the electronics to be much less susceptible to faulting when the inductive load kicks on/off.
In an old house, many codes permit wiring ground and neutral together at the outlet. This will allow modern electronics to function, under circumstances where they have separated ground and neutral internally and expect a three wire system. It will also cause circuit testers to report that the system is a properly wired three wire system.
What it will not do is provide you the additional measure of safety in the event of a neutral fault. By using a GFCI outlet, you can gain back a considerable measure of this safety.
About the Author: Jim Locker is a technical guy who has done a lot of real estate investing and landlording. The experiences he writes about and advice he gives are either first hand, or in answer to specific questions posed by others. He is commonly known as jiml8 around the internet.
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