Posted: 3/15/2008 1:28:55 PM EDT
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My Mother-in-Laws house was built before the standard 3 prong plugs. The junction boxes where the plugs mount appear to be PVC....How do I ground a new 3 prong plug? In other words where do I attached the ground terminal on the new style plugs? I replaced 1 plug and just left the green terminal empty. She uses those 3 prong adapter plugs on a lot of equipment. |
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My Mother-in-Laws house was built before the standard 3 prong plugs. The junction boxes where the plugs mount appear to be PVC....How do I ground a new 3 prong plug? In other words where do I attached the ground terminal on the new style plugs? I replaced 1 plug and just left the green terminal empty. She uses those 3 prong adapter plugs on a lot of equipment. My 1st ? would be ... Is there a grounding conductor pulled to these PVC J-boxes ? Like duh ... the PVC boxes are not original so, was there never a ground to begin with? Back when conduits, the old BX, and J-boxes were metal, they were (more or less) effectively grounded. Now there has to be a designed/intentional ground. If your wiring is in conduit, it would be relatively easy to pull grounding conductors in. If not, you've got a bigger problem. FWIW ... a 2-wire device, cord, receptacle isn't going to be grounded anyway. This might be a good time to have a good electrician check the house. An honest one will give you good and bad news AND tell you when its OK to leave well enough alone. Good luck. Stay safe |
From what I can see, the newer extension on the house has the copper ground wire in the wiring and those plugs are 3 prong. the original part of the house, 3 bedrooms is only 2 wire (black / white), no ground wire and the Black Plastic boxes have no metal portion in them. I can see the old two wire routes are not in metal conduit. the black plastic boxes are mounted with metal braces to the studs, so they are not grounded themselves. What are the risks of replacing the 2 prong outlets with 3 prong ones and leaving the ground open? As far as i can tell that would be just like what she is doing now, (when she uses the 3 prong adaptor on the plugs). |
Thats my understanding of GFI also. They also need that third ground wire. Still wondering what the difference is in installing 3 prong outlets with a dead ground, and using an adaptor on the plug? |
Possible electrocution in the event the plugged-in device has a short. That third wire allows the short to run straight to ground, instead of grounding through you. Not recommended. One alternative to GFCI outlets is a GFCI breaker in the electrical panel. |
GFIC will not work properly, though it may kinda work. There is no difference between a 3 prong outlet with a dead ground and an adapter. How big is the house? Have you considered running your own ground wires? As a side note, make sure your *house* is grounded. One of my coworkers recently found out his house was not and made the builder fix it (it's unlikely you'll be able to make the builder fix it in your case.. his was newish). |
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For the record I am an electrican. GFCI outlets (and breakers) measure the current flowing through the wires. What is supplied on the "Hot" (Black) wire versus what it measures returning on the "Neutral" (White) wire. If there is an imbalance caused by a faulty piece of equipment (lamp, heater, etc.) causing current to flow outside of the circuit (through you) it disconnects the power. This is actually covered (read REQUIRED) in the National Electric Code if you are replacing 2-prong outlets with 3-prong outlets that dont have a grooung wire. Don't ask me the section, my book is at the office. Using the GFCI takes the place of the third (Ground) wire. It is not the perfect solution but it does work. Without the GFCI, and using un-grounded outlets (old 2-prong or 3-prong w/out a ground wire) leaves you open to electrical shock if there is a fault with your equipment. |
Ok so to find the first outlet in the curcuit I disconnect the black wire from 1 outlet to see how many other outlets lose power. should I replace all the outlets with GFI ones or just the first one in each room? |
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If FMWright is "right", and I'm not certain he is about the GFCIs working w/o a ground, you are looking for gold and silver screws on the GFCI marked "load". They are the hot & neutral screws for the wires that will feed up to 5 duplex outlets "downstream" of your GFCI. ("line" is where the feed wires go) IF this does work, the GFCI will correctly protect the next 5 receptacles. FWIW ... Home Depot, etc. have an inexpensive plug-in GFCI tester to verify with.  Stay safe |
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A GFCI does not require a ground for anything. It is comparing the hot and neutral currents. If they do not match within ~0.005 amps the circuit is turned off. The only thing a GFCI wil not protect against is getting across the hot and neutral with NO other leakage path. This is so rare that using a GFCI to replace an ungrounded receptacle is allowed. You can even put 3 wire receptacles downstream as long as you attach the stickers that say "GFCI protected" and "No equipment ground" to the cover plate. The stickers are in the box with every GFCI receptale and breaker. |