Have old wiring

Old 10-10-13, 09:59 AM
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Have old wiring

Live in an old house, recently found the only two-prong outlet not replaced with a 3-prong outlet. Can I just replace it with a new 3-prong outlet? I know there has to be a ground wire in there.....Thanks.
Old 10-10-13, 10:19 AM
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Absolutely not if there is no ground and if there is no ground at the other 3 prong receptacles they need to be replaced with two prong receptacles.

You can replace a two prong receptacle on an ungrounded circuit with a three prong GFCI receptacle but that only improves safety. It does not provide a ground.

If there is no bare ground wire in the box and it is wired with nonmetallic cable then it is probably not grounded. In a very narrow time frame a metal box was grounded externally. To determine that take the cover off the breaker box. If you see several #16 bare wires then the box is probably grounded.

If the box is nonmetallic and there is no bare (or green) wire in the box it is ungrounded.

If it is a metal box and supplied with metallic cable it may be grounded. Test from hot to the metal box. 120 volt indicates a ground. However you may get this reading with older BX cable also. Older BX cable with no bonding wire/strip may not provide an adequate ground.

If the box has a green wire the circuit is probably grounded.

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