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Will a GFCI receptacle that is not grounded still function properly?
Saturday, July 21, 2018
The purpose of a GFCI receptacle is to trip when it senses that any electric current has leaked from the intended circuit, which may be causing someone to be shocked, and quickly to cut off the current to avoid possible electrocution. GFCI protection is required for receptacles in all the wet areas of a home, such as the kitchen, bathroom, garage, laundry and exterior, along with spa tubs and pools.
The device will still function properly if the ground slot is not connected to a ground, which we see occasionally in pre-1960 houses that have GFCI-receptacles in the kitchen and bathrooms supplied by ungrounded two-wire cables. The GFCI is considered an alternative to grounding by the National Electrical Code (NEC) and a two-slot ungrounded receptacle is allowed to be replaced with a three-slot GFCI receptacle; however, the receptacle must be marked as having “NO EQUIPMENT GROUND” on the cover plate. This is because, although it is considered safe, some appliances require a ground connection in order to work properly, and the notification alerts a user of the receptacle. Manufacturers of GFCI receptacles include a sheet of small stickers in each box to help you comply with this safety requirement. Because a GFCI-receptacle at the head of a string of receptacles will provide shock protection for all the receptacles downstream, it is typical for a GFCI-receptacle in one bathroom to protect the receptacle in another bathroom that does not have a GFCI-device. Also, one GFCI-receptacle in a kitchen can protect several others nearby. All the protected receptacles must have a “GFCI PROTECTED OUTLET” sticker on the cover plate, and any protected ungrounded receptacles are required to have a “NO EQUIPMENT GROUND” sticker too.
Although an ungrounded GFCI receptacle will function properly, it cannot be tested with a three-light circuit tester with a “GFCI TEST” button or most electronic circuit testers, like the ones shown below, because they shunt a small amount of current to the ground slot to simulate a ground fault. Unfortunately, when there is no ground connection the test won’t work. But the test button on the front of the GFCI-receptacle will trip when tested, and that is how we verify that they are alright.
Also, see our blog posts What electrical hazards does a Ground Fault Circuit Interrupter (GFCI) NOT protect against? and Does a receptacle outlet that is not readily accessible still need GFCI protection? and Where are GFCI receptacle outlets required?
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