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.
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.
It is possible that your outlet boxes are grounded. Check for a bare ground wire in the box, probably connected to the metal box. If so, you need to test the ground and make sure it's good, then buy a self-grounding outlet and install it and you're good to go.
Otherwise, it's OK only if you put a GFCI breaker or outlet upstream of the new 3 prong outlet, and you put a sticker on the new outlet that says "GFCI PROTECTED, NO EQUIPMENT GROUND". Or you can replace the outlet with a GFCI outlet, which really ought to be labled "NO EQUIPMENT GROUND". Or you can run a separate green wire back to the breaker box or ground electrode conductor (that big bare copper wire that comes out of the breaker box and goes to your water meter.) I've run a few green ground wires in my 55 y.o. house, and installed an ungrounded GFCI in my kitchen because it was too hard to route a ground wire there.
BTW, the reason it's worse than the old 2-prong outlets is if you install
3-prong outlets without connecting the ground, you give the *illusion* that the outlets are grounded.
Testing for a grounded box is not as easy as it sounds. Most electrical testers draw too little current to actually test the Equipment Grounding Conductor (EGC). Only a test conducted using special tools or techniques will actually test the EGC. Call the tool rental places to find one that rents an Ideal suretest.
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.)
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.
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.
That's why I glossed over it. Before renting a tester, or rigging up a test load and hoping you don't start a fire with it, it would make sense to test for a ground using a cheap neon light tester or one of those little outlet testers. If they say your ground is good, then it is worth doing further testing.
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:
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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.
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:
An outlet string has no grounding means to the house ground, but downstream outlets are protected by the first outlet, which is a GFCI.
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.
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.
The GFCI fails such that it does not trip when it should.
An appliance connected to one of these outlets develops a ground fault, such that it's metal parts become "hot".
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:
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.
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.
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.
What kind of cabling do you have? It's perfectly acceptable to use the conduit as the ground if it's in metal flex conduit. Thne you only need to run a short stub from that to the ground terminals on your outlets.
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