I have an older home with wiring that does not have a ground wire. I am changing the old receptacles and putting in three prong receptacles. how can I ground these receptacles without changing all the wiriing?
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What do you mean by "older home"?
Are you positive there is no ground?
At one time the ground was connected to the box on the outside.
edit - my house was built ~1960. the ground wire was connected to the metal box, there is no visible ground wire in the box.
bobl Volo Non Voleo Joe's cheat sheet
Edited 8/14/2002 12:59:56 PM ET by bobl
the home was built in the fifties. all recptacles have two wires in each of the metal boxes. no third (bare copper) ground wire. the main box is grounded to the water pipe and a rod outside
Are the branch wires in metal conduit, or are they old "rag wire" non-metalic wires?
If they are in metal conduit, that can sometimes be used for the grounding circuit.
Otherwise, you either have to (i) run a new, separate ground wire, run a new grounded branch circuit wire, or (iii) stick with ungrouned type outlets.
Do not use a bootleg ground. (If you know what <i>that</i> is, you should know not to use one. If you don't know what that is, all you need to know is not to use it.)
Edited 8/14/2002 4:46:27 AM ET by Bob Walker
metal boxes and old cloth type covering.
Three approaches, in order of hardest to easiest:
1. Rewire the house with modern NM
2. Pull a separate equipment grounding conductor to the boxes where you want grounded outlets. These conductors must be tied to the grounding electrode system.
3. Install GFCI outlets. This is the simplest method of getting around having no ground, but wanting to have "grounded" (i.e. 3 prong) outlets. Determine which outlet is the first in what is hopefully a "chain" of outlets on the circuit, install the GFCI outlet there, and feed the remaining outlets from the GFCI (the "load" side of the outlet). Mark all remaining outlets with the "GFCI Protected" and "No Equipment Ground" labels that typically come with GFCI outlets. This is an acceptable practice per the NEC.
"Boot-legging" as the previous poster warned not to do, is when you tie the grounded (i.e. neutral) and grounding (ground) terminals of the outlet together via a short pigtail. This will cause the outlet to look properly grounded when tested with a cheap outlet tester, but can pose a danger as neutral current can potentially be traveling on equipment chassis, etc... in other words, parts that shouldn't have current flowing through them normally may now be live. It's done in a lot of older homes, and is a bad and dangerous practice.
Happy wiring!
...and any time you daisy-chain GFI outlets (hook up down-stream outlets to one GFI to get GFI operation for all of them) be SURE to confirm that the downstream outlets do go dead then the GFI is tripped.
When doing new wiring it is quite easy to make sure that no other source of current exists in a downstream circuit but doing retrofits to existing wiring you can not be as sure (without x-ray vision to see thru the walls or doing more elaborate wiring diagnosis before starting).
The purpose of GFI is to stop the current flow. Shared neutrals and other things will cause trouble with this and you won't know it without careful testing to make sure. If you don't know how to do that kind of thing then please call an electrician to do it for you or confine yourself to installing GFI outlets that do not provide down stream service.
Or just put a gfi in every box.
Gotta be cheaper than paying an electrician to come in and do a bunch of testing, and/or running new wires.Quittin' Time
I have to agree with the person who said to not replace the outlets with new grounded ones unless you are actually putting in a proper ground at that time (i.e. not just planning to put one in at some time). We encountered many houses during our search that had 3 prong receptacles which didn't pass the test. That immediately set up a red flag which made me look for and find other problems. In our local housing market, we noticed a real premium with 1900-1920 houses with 2000 infrastructure. Speaking of premiums, I'm waiting to see how much ours is reduced by the new water and electric services.
The remainder is my thoughts on why one would seriously consider upgrading.
After looking at the ungrounded two-wire braided sheath 1950's romex in our place, I decided to replace it. Fortunately after the service panel change, this only constituted about 20% of the remaining wire in the house, and since it was likely put in as a retrofit of the first generation knob and tube, it was only stapled to joists in accesible areas of the attic and basement. I currently have 3 ungrounded outlets in the house. They are on two separate circuits, and connected via unaccesible knob and tube in the first and second floor ceiling rafters. I did put both of the circuits on an arc fault breaker (about $30 each) and where possible have replaced the light bulbs with compact fluorescents. At present those receptacles are used for CO detectors and nightlights only.
In your case, before deciding to not replace the wiring, take a look at as many of the circuits as possible. It is possible that the wiring is only stapled in accessable areas, and it would therefore be trivial to use the old wiring to pull new. It might be advisable to hire an electrician for an hour or two just to come out and look over your place. I was very fortunate to get connected with a really great father-son team based on a recomendation from a neighbor. I have to admit, how they wanted to do it was completely different that what I thought, and more and more I see how right they were. Remember, 1 hour of their time equals a 1000 ft roll of romex. Sometimes the longer way is much much less expensive.
Also, after looking at a number of the older metal boxes, I was not comfortable with their quality and opted to replace them with new old-work brown phenolic boxes along with the wiring. In my case, the boxes used a funky type of cable clamp which IMHO had a greater likelyhood of cutting the insulation than it did in protecting the sheath from abrasion. The combination of a metal box with potentially abraided cable and an ungrounded receptacle still gives me the willies.
I know there are millions of houses out there with the wiring you describe which will never have a problem. I had several reasons to change my system over to as much new stuff as possible. One was my wife, who wanted grounded outlets even for circuits that used only ungrounded devices such as clock radios. Another was to add value to the house. Based on our recent house hunting, I was aware that I had a very different feeling about a house which had lots of white romex in the basement versus one with old black cloth wire and knob and tube. We even negotiated a $3000 concession in order to do the service change and upgrades. And third was just my own comfort knowing that things were good. We had lived in a number of rental places during grad school and fellowships, and I tell you, knowing what I do now, I'd never ever go back into those firetraps (IMHO).
Good luck. The more you know about your house, the better.
GFCI outlets or circuit breakers can provide a lot of protection. However, they very occasionally do not work when new, and somewhat more frequently fail to function correctly over time. They all come with a built-in test button, but my understanding is that they must have a separate ground in order for that test button to actually test the GFCI, and they should be tested frequently. Thus I would have some concerns about simply installing GFCI outlets on a two wire circuit. GFCI breakers can be installed in a circuit breaker panel, but those breakers are quite expensive and also are known to occasionally require replacement after a couple years. Another option might be to run a couple feet of new romex from the circuit breaker to a junction box next to the panel, install a GFCI outlet there (which could be tested because of the ground wire back to the panel) and use the GFCI to then supply the existing two wire circuit. This would be the least expensive, even if you have three or four such GFCI outlets beside the panel. As has been pointed out, the most desireable solution, if money and/or time were no object, would be to replace the existing wire throughout. Good luck.
You don't need a ground to test a GFCI using the internal test button. GFCI's have current transformer in then that both the hot and neutral wires pass through so that as long as the current is balanced the signal cancels.
To test it you need to unbalance the current. That can be done with a test resistor that one end is connected to the hot side AFTER the transformer and the other to the neutral BEFORE the transformer.
Thanks for the clarification. Installed GFCI's on screened porch several years ago where feeds were in conduit in brick columns. Conduit was badly rusted and was the ground connection. Couldn't get any of the GFCI's to trip in that situation but when I removed and installed in circuit made up of new romex, they tested and tripped as expected. Might have been some other problem there. Don
This is a good demonstration of why conduit grounds, without a redundant ground wire, are such a poor idea. A little corrosion or abuse and you loose the ground.
Anything short of rewiring ea. receptacles is a short cut. To install GFCI receptacles might be safer for personnel but that settup does not protect electronic equipment. Electricity takes the easiest path to ground. The best way to protect yourself, your home, and your equipment from stray or faulty currents is to provide an easy and safe way for those currents to go to ground. Voila! A grounding wire in NM cable does the trick. Also the NM cable made these days can stand higher temperature and more abuse than the old cable. Seems like an easy choise to me.
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