Two prong receptacles, often found by an inspector in an older home, that are connected to two-wire cables, do not have the ground wires, which protect people and electrical devices in case of a ground fault. Upgrading 2-Prong Outlets to a new three-prong or GFCI receptacle in the same receptacle box without any rewiring is possible as long as the box itself is grounded.
Metal boxes attached to armored, or BX cable, which is a type of wiring commonly found in old homes, are typically found to be properly grounded. The armored or BX cable’s flexible metal jacket serves the same purpose as a dedicated ground wire.
If the box is not grounded, a GFCI can be installed or an electrician can be hired to fix the wiring.
GFCI-Ground Fault Circuit Interruption
The image to the right is a GFCI that was installed to replace the old, 2-prong ungrounded wall receptacle in an older home. This GFCI must be labeled as a GFCI without an equipment ground.
Simply replacing an older 2-prong outlet with a 3-prong outlet can be hazardous, because the receptacle will appear to be functional with a ground, but in fact there isn’t one. If someone were to plug a faulty 3-prong device into that “fake” grounded receptacle, a shock hazard is very likely. Electricity moving through the device casing would create an energized surface from which a person could be electrocuted.
Another problem with replacing ungrounded 2-prong receptacles with 3-prong one is in relation to surge-protection device, which relies on a solid ground to route any transient activity. The ungrounded receptacle would not be able to protect the device from a surge.
It is permissible to replace a 2-prong ungrounded outlet with a 3-prong GFCI outlet. But, it must be labeled as “GFCI Protected Outlet, No Equipment Ground.” Even though there is not a grounding conductor, there is still some protection against shock provided by the GFCI.
Play it Safe
The bottom line is, play it safe. To do electrical receptacle upgrades in a manner that will provide the most protection to the inhabitants of the home, have a licensed electrician who has the proper equipment and knowledge to do it right make the upgrades.
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