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Three very old non-grounding type electrical receptacle outlets

To Ground A Two Prong Outlet

Dear Mr. Electrician:  What do I need to do to ground a two-prong outlet?  I want to replace the two-prong outlet with a three-prong outlet. Answer: To ground a two-prong outlet and replace it with a three-prong, you must determine your options.  Sometimes it is just a matter of changing a two-prong outlet to a new self-grounding three-prong outlet. NOTE: Some text links below go to applicable products on Amazon.  As an Amazon Associate, I earn from qualifying purchases.  Using my links helps to keep this website FREE. Table of Contents DOES MY TWO-PRONG OUTLET HAVE A GROUND? TESTING AN OUTLET FOR AN EARTH CONNECTION STEPS TO REPLACE AN OLD OUTLET WHEN THERE IS NO GROUND AT THE ELECTRICAL RECEPTACLE INSTALL A REPLACEMENT FOR AN UNGROUNDED OUTLET ANOTHER EXAMPLE OF AN UNGROUNDED OUTLET REPLACEMENT DOES MY OUTLET HAVE A GROUND? The BIG question is whether or not you have an approved grounding conductor in the existing outlet box, which would allow you to ground a 3-prong outlet. Approved grounding conductors can be a separate wire specifically for grounding purposes, metal conduit, the metal armor of type AC cable (BX), short lengths of flexible metal conduit (FMC), short lengths of sealtight (LFMC), metal enclosures, cable trays, and metal raceways including Wiremold metal raceway.  See articles 250.62,  250.70,  250.109, and 250.118 in the National Electrical Code (NFPA 70). Some MC cable metal armor may be approved as a grounding conductor, but you would need to check the labeling on the cable to confirm.  Article 250.118(10).  Even if the MC cable armor is not an approved grounding conductor, the metal armor must still be grounded using approved MC connectors. Top Of Page If you have an old house with two prong receptacles, it could have been initially wired by one of several wiring methods available at the time.  Knob and tube wiring has no grounding conductor.  With proper fittings, BX cable has grounding through its metal armor.  Metal conduit is grounded if it is installed correctly. Non-metallic cable (NM), before it was called Romex, was made with and without a grounding conductor.  If it has a grounding conductor, it is most likely smaller than the other conductors in the cable. Top Of Page TESTING AN OUTLET FOR AN EARTH CONNECTION You can quickly check for a ground with a voltage tester before you remove the old outlet.  Put one lead of the voltage tester on the metal screw for the wall plate.  Make sure there is no paint on the screw.  Check for voltage by putting the other lead in one of the slots in the outlet.  Then put it in the other slot.  The smaller slot should be the live one, and the bigger one should be the neutral one. If one of those connections indicates power, you probably have a grounded connection to the box.  You can also use a pigtail light bulb socket for this simple test. If the test indicates that you do not have a ground connection at the electrical receptacle outlet's location, see below to ground a two-prong outlet by adding a grounding...