i was reading in the march 2005 isssue about wiring…there were some myths, and one was that you cant gfi an old two wire system…
in fine homebuilding they said you can no problem, and showed replacing with a gfci…they said the only problem was using a 3 prong plug on a 2 wire circuit…so if you replace with a gfi, whats to stop someone from plugging in a 3 prong plug? or do they make a two prong gfi receptacle, as i have never seen one…Any replys welcome thanks Steve Harbauer
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Steve,
My understanding is that the GFCI obviates (how's that for a $3.00 word) the need for a ground wire. Since any stray current would trip the GFCI the ground is not needed. In fact, I believe that all downstream receptacles can be 3 orifice type as well as long as they are labeled as such. You know, those stickers that we always take out of the box, look at and throw away. I may be wrong but I was told that using GFCI outlets is the easiest and cheapest way to upgrade from the old 2 wire outlets to let you use 3 pronged equipment.
chris, thanks for the reply! yes definitly cheaper then tearing up drywall, to run another wire...perfect for the bath im going to upgrade
"they said the only problem was using a 3 prong plug on a 2 wire circuit.."
But the GFCI is not an adapter.
The grounding pin on a properly wired system provides a path for fault current to be returned and keeping the fault current from "energizing" (making electrical hot) any exposed metal on the device. If the fault current is high enough the breaker will trip.
An grounded quipment pluged into a grounding style receptacle, that does not have a ground, then the equpment might become energized. But if anyone touches it and forms return path the GFCI will detect that and immediately trip.
Thus the GFCI provide equivalent personal safety.
However there are 2 place where the GFCI should not be used as a substitute for a real equipement ground.
On equipment where false tripping of the GFCI can cause property damage. That includes sump pumps, refigerators, and freezer. They should be on circuit with a true ground and NO GFCI.
The other is equipment with surge arrestors. The surge arrestors need a true ground for full protection against surges. They can be used with or with a GFCI, but need to the true ground.
Thank you Bill, I've been wondering about that of late.
Been replacing old knob&tube wiring and grounding all boxes as I go, but the old fuse box has yet to be replaced with a circut panel.
A couple of the circuts have 12-2 Romex without a grounding wire, running from the fuse box to junction boxes where the new wiring was tied in.
My thoughts were to have that old wiring replaced with new 12-2 when the circut panel gets installed.
Do you see any problem in this? Thanks
A person with no sense of humor about themselves is fullashid
If I follow you you have upgraded circuit and they use grounded wiring, but they are still feed from a juntion box which is not grounded.That is fine unless you are also installing grounded receptacles.But you can either install a GFCI to protect those recetacles or run a separate ground wire from the junction fuse panel ground.Or even just put a piece of tape over the ground pin in the receptacle so that you don't depend on that unconnected ground. Of course that is technically not to code, but if it is your house and you are progressing to improving each thing as you go along I don't see a problem.
Thanks.
A person with no sense of humor about themselves is fullashid
Bill, thanks for clearing that up!!! true its not an adapter, but it allows you to plug in a three pronged plug...so as long as the gfci can take care of any faults then it seems all good to me!