Old homes often have ungrounded two-wire conductors carrying electricity throughout the home. (One wire was “hot” and one was “neutral.”) If you see receptacles that only have two slots and are missing the round hole, you can be sure two-wire conductors were used. This older wire isn’t nearly as safe as modern conductors because it lacks a grounding wire to direct electrical current to the ground in the event of a fault. (These faults are usually caused by deteriorated wire insulation.) Without a grounding wire to provide a path for this electricity, a person touching the metal housing of an electrical appliance could be electrocuted. However, in the event of a direct fault (in a grounded receptacle), the current through the ground wire would cause the circuit breaker to trip and the circuit would be de-energized.
So if you have two-wire conductors in your home, what can you do to make your home safer?
Before I address this question, let me point out something that homeowners occasionally do that you SHOULD NOT do: simply replace two-prong receptacles with three-prong receptacles. Doing this only makes your home look safer while in reality, your receptacles are still unsafe because they still lack a grounding wire.
Here are a few options for homeowners:
- Have your home completely rewired. An electrician will remove all of the old wiring and replace it with new wiring. As you can imagine, this is very expensive but it will ensure every circuit in your home is grounded.
- Replace the first two-prong receptacle on the circuit with a GFCI receptacle and the rest of the receptacles on the circuit with normal three-prong receptacles. (This upstream GFCI-receptacle will provide protection for all downstream receptacles.) Although doing this does not provide a ground, it does make each receptacle safer because now the GFCI-receptacle will instantly trip and de-energize the circuit if it senses the electricity taking a path outside of the intended circuit, such as through a person! It does this by monitoring the current to make sure it is always balanced between the hot and neutral wires. A difference of about 5 mA will cause it to trip.
- Replace every two-prong receptacle with a three-prong receptacle and then replace the breaker for that circuit with a GFCI breaker. (This would achieve the same result as option 2, but it would cost more than option 2.)
Not only are the second and third options cheaper than the first option, but they also provide the greatest level of safety for people.
I should mention, options two and three can drive a home inspector nuts!
With the second option, s/he will see a GFCI receptacle, plug in their three-prong receptacle tester and attempt to trip it using the button on the tester, and nothing will happen! They will assume the GFCI receptacle is damaged and should be replaced, but it’s not damaged, just ungrounded. Hopefully before writing up the receptacle as defective and unsafe, they will attempt to trip the GFCI circuitry using the button on the receptacle. Doing this will de-energize the receptacle (and all downstream outlets) letting the inspector know that the receptacles should still be written up as ungrounded receptacles on a GFCI-protected circuit.
Similarly, with the third option, s/he will plug in their three-prong receptacle tester and see that the receptacles have open grounds. They will then need to trip the GFCI breaker in the panel and make sure all of the receptacles that tested as having open grounds are now de-energized. They would still write up the receptacles as ungrounded receptacles on a GFCI-protected circuit.
In a perfect world, ungrounded GFCI receptacles and ungrounded standard receptacles on GFCI-protected circuits would have a stickers on the cover plates specifying that they are ungrounded receptacles with GFCI protection.
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Note: While GFCI-protected outlets will protect people from serious injury, they do not provide surge protection. Surge protection devices (SPDs) protect sensitive electronic equipment, so surge protection should also be used. (Some point-of-use surge protectors only provide protection when they are plugged in to grounded receptacles.)
Inspection Stuff 