Three prong outlets

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I have an older house and need to replace a few old outlets, but there is no easy way that I know of to run a ground for three prong outlets. Is it OK to replace an old two prong outlet with a three prong, but not use the ground? I know this is not the best choice, but I figure this is no worse than the old outlets with an adapter plugged in for the vacuum cleaner. I can handle most handyman electrical type stuff if I have to, but don't want to tackle a re-wire. Any suggestion or advise is appreciated.
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cnavarro wrote:

It will not meet code, and it is less safe than what you have now. How you say? When someone sees a grounded outlet they assume the outlet is grounded. You might, or might not, remember it is not, but how about someone working on your home or the next owner.
This is a real no no in my book.
It is usually not that hard for to run a ground for someone who knows what they are doing and knows all the tricks. So get a pro out and let them figure it out.
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Joseph E. Meehan

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As I recall, the NEC says the ground terminal of a GFCI outlet is an acceptable safety ground, even if not connected to other ground wiring.
Nick
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snipped-for-privacy@ece.villanova.edu wrote:

Nope. The ground terminal of an ungrounded GFCI is absoluely not acceptable as a safety ground. The NEC says the GFCI provides "equivalent protection" to that provided by a grounded outlet, so that grounded equipment can be connected to the GFCI without a functional ground. The ground terminal should not be connected when using a GFCI to protect "downstream" outlets. Those outlets should be labeled "No equipment ground" and "GFCI protected". The GFCI itself should be labeled "No equipment ground". (It is considered sufficiently obvious that a GFCI-type outlet is "GFCI protected" without needing a label.)
--
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Sounds safe to me, in the sense of preventing electrocution...

Why not?
Nick
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snipped-for-privacy@ece.villanova.edu wrote:

Yes, it is safe to protect grounding-style outlets with a GFCI where no actual grounding means exists. However, on such an outlet, the ground terminal still does nothing, and it is not effective or safe to use the GFCI ground terminal as the origin of a ground wire. It does not provide a ground.
Why not connect the ground terminals downstream? Suppose we have the following situation:
1. An outlet string has no grounding means to the house ground, but downstream outlets are protected by the first outlet, which is a GFCI.
2. The outlet string is wired with a system that includes a ground wire, but the feeder supplying power to the string does not include a grounding means to the system ground. This seems to happen fairly frequently, especially when an older house is remodeled.
3. The installer connects (incorrectly) the ground wire to the GFCI and all outlets downstream. The equipment grounds of all equipment connected to this outlet string are now connected together by the ground wire.
4. The GFCI fails such that it does not trip when it should.
5. An appliance connected to one of these outlets develops a ground fault, such that it's metal parts become "hot".
6. The defective GFCI does not trip.
Now, because the ground wire is connecting the grounding means of all appliances on that outlet string, and because the ground wire is not actually grounded, _all_ the appliances on that outlet string share this ground fault, and their grounded metal parts are now "hot", also.
This situation is also true even if the GFCI is functioning properly if the ground wire and connected appliances have no path to ground. However, if the GFCI is working properly, the next person to touch any of these appliances will provide the ground path, tripping the GFCI.
Replacement of non-grounding receptacles with grounding-style receptacles protected by a GFCI, including not connecting a grounding connector from the GFCI, is covered in 2002 NEC 406.3(D)(3)(b) and (c). See also: http://dotznize.com/electric/?a=gn
--
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snipped-for-privacy@ece.villanova.edu wrote:

Nick With a low impedance grounding pathway any fault causes the immediate opening of the Over Current Protective Device which usually avoids the user experiencing a shock. With GFCI protection the device opens the circuit after the shock has begun and even though it prevents direct injury by the flow of current it will not prevent injuries caused by falls or physical startle reactions brought on by the shock. -- Tom H
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Even a high impedance ground (eg 10K ohms) might help with that...
Nick
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wrote:

Do you know where in the NEC it says this (I have the NEC, so I'd like to look at the section). What if the outlet box is metal and the wires are MC all the way back to the breaker box? Does the metal cladding suffice for a ground (i.e., could you attach a ground to the metal outlet box)? The NEC seems ambivalent on this point.
--
Bob in CT
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Bob in CT wrote:

Replacement of non-grounding receptacles with grounding-style receptacles protected by a GFCI, including not connecting a grounding connector from the GFCI, is covered in 2002 NEC 406.3(D)(3)(b) and (c). See also: http://dotznize.com/electric/?a=gn
In section 330.108, which covers metal-clad cable construction specifications, the NEC states "Type MC cable shall provide an adequate path for equipment grounding as required by Article 250." Article 250 covers grounding in detail I would say the key here is to actually test the ground connection in question. Because the testing procedure can create a momentary hazard if there is a bad ground connection, I am going to hide under the table and not give instructions on how to do it.
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Bob in CT wrote:

If the wires were in type MC metal clad cable they would include a green insulated grounding conductor. If it is Type AC armored cable then it has an aluminum bonding strip inside the interlocking spiral tape armor. The aluminum bonding strip assures a low enough impedance that the armor is listed as an Equipment Grounding Conductor (EGC). With either of these you would bond the grounding terminal of the receptacle to the EGC. In the case of type mc cable the green insulated wires from the cable are spliced together with a sufficient numbers of jumpers to connect one to the metal box and one to the grounding terminal of each strap or yoke that is mounted in the box. In the case of type AC cable the bonding jumper is terminated to the metal box and to the receptacle grounding terminal. The box is grounded by the cable connector to the bonded armor of the type AC cable.
If the cable has neither a green insulated grounding conductor or an armor bonding strip then it is the older "BX" cable. BX was the trade designation used by the first manufacturer of metallic jacketed cable. That cable does not contain an EGC so it cannot provide a ground pathway. That is the only metallic jacketed cable with which you would use a GFCI as a substitute for the EGC. With "BX" cable there is a real risk of energizing multiple portable appliances from a single fault because the impedance of the unbonded armor is often high enough that the fault current flow is not high enough to trip the circuit over current protective device. In that case the armor will be heating until sufficient heat develops to fault the grounded to the ungrounded current carrying conductors or to ignite the combustible building materials with which it is in contact. The only saving grace for "BX" cable is it will usually conduct enough fault current through it's jacket to trip a GFCI or AFCI. -- Tom H
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Here comes the "heating element" fairy tale again:

Cite of a reputable, independent source (Translation: besides you) who says this, please.
Cite of an act by a government regulatory body declaring this type of cable unsafe and mandating that it be removed from buildings? Cite of any reputable historical compilation of fires caused by this situation?
Don't worry, nobody could produce them last week, so I know you won't now.
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TP / Network Man __________________________________
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We have about four now. Tom, volts500, me, and my coauthor in the electrical wiring faq. There's lots of people who figure the four of us are reputable ;-)

Cite someone, _anyone_, who suggested this was the case.
The hazards of aluminum wire are extremely well known. Nobody questions that aluminum wiring can be very hazardous in some circumstances.
Most jurisdictions now have restrictions on its use.
Yet, _no_ jurisdiction I know of has mandated its removal.
So, why would it be any different for any other similar hazard?
The Canadian regulatory body (CSA) and provincial government regulatory bodies have _all_ banned the use of BX cable sheath as a grounding conductor.
They must have had a reason, eh?

Can you cite one for aluminum? Do you doubt that aluminum can be hazardous?
Here's one where BX contributed:
http://www.emergency-management.net/mgm/page2.pdf
check out page V-11. What kind of wire was that? ;-)
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Chris Lewis, Una confibula non set est
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Chris Lewis wrote:

Just as expected. You can't.

If what you claim is true, it would be. More sidestepping and tapdancing snipped. I've made my point.
Fairy tale.
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Nonsense. Clear example: the hazards of aluminum wiring are well known. It does cause fires. I've _personally_ seen five burned out aluminum connections, three of which _would_ likely have caused a fire except we were there to notice and put it out.
Have they mandated a removal of all aluminum wires from buildings?
No.

Not only are you ignorant, you're dishonest.
The link I provided was to the report following 85 people being killed in the 1980 MGM Grand hotel fire in Las Vegas. _Because_ of cable armor corroding, overheating, and starting a fire.
I don't think any of those 85 people considered it a fairy tale.
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Chris Lewis, Una confibula non set est
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Aluminum wiring does not cause fires. Poor connections and improper installation causes the fires. That is why it is not mandated to be yanked out of houses as it can be corrected. Aluminum has long been used as a conductor for lines from pole to house also with no problem. Ed
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I agree with you (tho some experts don't) in that bad workmanship/materials is the key to problems with aluminum. I was using "aluminum wiring" in a more general sense - _including_ the range of typical installations (wrong devices, using push-in terminals (the cause of my near fires) etc) seen in practise.
The same is also true with using BX armor - using it as a ground is certainly now a no-no. Especially here where it hasn't been legal for a very long time. That "can be corrected" too.
That wouldn't necessarily stop a regulatory agency issuing a recall.
Or, more to the point, if you assume that it "can be corrected", then they could easily require mandatory inspections of aluminum wiring and repair of problems instead. As many jurisdictions do with furnaces (NG installations have mandatory inspections every 3-10 years here).
But they haven't done that either.
So we have a situation where a regulatory body _could_ have chosen to take actions for a known and well-established hazard, but has chosen not to.
Thus, the fact that regulatory bodies have not required BX removal (or inspections) doesn't mean that regulatory bodies believe that BX-used-as-grounding is "okay".
--
Chris Lewis, Una confibula non set est
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Chris Lewis wrote:

So, you've just admitted that your "example" is BULLSHIT. Nothing more than BULLSHIT.
Well, I guess it's still a fairy tale too.
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Of coure not. In fact, it proves it even more. With faced with a _similar_ hazard (bad aluminum installations versus BX cable used as ground), they didn't recall it (as many people wanted). They didn't even insist on mandatory inspections. They just modified code a bit.


Only in your world. Which one is that?
Still claiming that 85 dead people in the MGM Grand Hotel, in part due to cable armor being used as a ground, in 1980 was a fairy tale?
Or are you ignoring it, hoping nobody will notice?
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Chris Lewis, Una confibula non set est
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snipped-for-privacy@ece.villanova.edu wrote:

You are right in that I did not consider GFCI. I believe it is allowed and many consider safe to use GFCI with some restrictions. I would not do this myself since I just don't like the idea, which is likely why I did not think of it in the first place. If you are going to have a plug with a ground, it should be grounded, IMO!
On the other hand as noted, they still make plugs without grounds, but I would be hard pressed to go that route. If you are going to do a job, do it right.
Thanks for the comment.
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Joseph E. Meehan

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