GFCI on 2-wire circuit

Looking at an older (1950's construction) sweat-equity house the other day,= I discovered some of the outlets are 2-prong, some properly-grounded 3-pro= ng, and some 3-prong with no connection to the ground pin. I have heard th= at GFCI outlets can be installed on 2-wire circuits, but does that help any= ?

Reply to
Richard Henry
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Does it help *what* any?

It certainly helps *you* from a safety perspective -- while a fault in the 'hot' lead within a device connected to a properly-grounded outlet would tend to blow a breaker if that 'hot' lead inadvertently contacted the (grounded) chassis, in this case, while the chassis will be hot, the idea is that with the GFCI the current that might end up going through you is small enough that, assuming you're generally healthly, you aren't going to be killed.

Reply to
Joel Koltner

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around here that is pretty much the standard installation, gfci is mandatory, only few outlets have ground

-Lasse

Reply to
langwadt

If only two wires run to a socket, modern code allows a GCFI socket with the ground hole plugged as a safe refit of that socket. Or requires a 'GCFI protected" sticker and a "no equipment ground" sticker. And the code is changing as we speak, so don't trust what I say...

Every so often I buy another copy of "Wiring Simplified" to look these things up. The one in my lap now is '40th edition'.

Reply to
whit3rd

discovered some of the outlets are 2-prong, some properly-grounded 3-prong, and some 3-prong with no connection to the ground pin. I have heard that GFCI outlets can be installed on 2-wire circuits, but does that help any?

You most likely have BX (metal coil/armor) going to each box that houses the existing plug.. BUt in the old days, they used to put a wire in there and many installers will just coil it up. the box itself if metal, would most likely provide you the ground you need for newer outlets providing this has the BX all the way to the box or some ground wire bonded on it some where.

If you have the older type metal coil with no ground thread in it, then may I suggest you tighten up all the connectors you can get to.

Having loose coupling/box connectors with your BX is going to generate some false trips with your GFCIs

Jamie

Reply to
Jamie

y, I discovered some of the outlets are 2-prong, some properly-grounded 3-p= rong, and some 3-prong with no connection to the ground pin. =A0I have hear= d that GFCI outlets can be installed on 2-wire circuits, but does that help= any?

Even more fun, those two prong outlets are not polarized; in my parent's house the hot/neutral isn't even on the same side from one outlet to the next... It wasn't important in the days when just a lamp and a radio were connected there. It caused all kinds of problems for me when I was in the basement with my several computers and complex sound system. I think part of the reason for the weird wiring was the GE Remote Control wiring. The house's electrical system was actually routed through a central relay panel controlled from several low voltage switches and one central main panel. Who knows what the electrical code was back then?

Reply to
a7yvm109gf5d1

day, I discovered some of the outlets are 2-prong, some properly-grounded 3=

-prong, and some 3-prong with no connection to the ground pin. I have hear= d that GFCI outlets can be installed on 2-wire circuits, but does that help= any?

I had that arrangement in my previous house (1960's construction) so I was = able to put proper 3-prong outlets throughout the house.

Our current house (built 1980) has three-prong outlets everywhere, but the = only GFCI circuit fed the garage (where a refrigerator was plugged in) and = the outside outlet. My 3-year-old son managed to trip the circuit by putti= ng a screwdriver in it, but didn't tell anyone, so the first clue we got wa= s when the garage started smelling bad. I have now installed GFCI's in the= bathrooms and kitchen, but not the bedrooms which I understand is now requ= ired by the latest NEC version (or is it IRC version?).

Reply to
Richard Henry

discovered some of the outlets are 2-prong, some properly-grounded 3-prong, and some 3-prong with no connection to the ground pin. I have heard that GFCI outlets can be installed on 2-wire circuits, but does that help any? Cannot say if it helps or not; i have one in a kitchen that i use for a toaster. Randomly it pops about when i plug it in or when i unplug it. "About" means anytime from instant of connect/disconnect event to 5 seconds later. Now the waffle iron does not make the GFI "fault". Go figure.

Reply to
Robert Baer

...then there is the ultra-modern spool-and-knob wiring...

Reply to
Robert Baer

discovered some of the outlets are 2-prong, some properly-grounded 3-prong, and some 3-prong with no connection to the ground pin. I have heard that GFCI outlets can be installed on 2-wire circuits, but does that help any?

I do not think Abbot & Costello's "who" is alive to ask...

Reply to
Robert Baer

discovered some of the outlets are 2-prong, some properly-grounded 3-prong, and some 3-prong with no connection to the ground pin. I have heard that GFCI outlets can be installed on 2-wire circuits, but does that help any?

yes a GFCI can be put on an (existing) two wire non grounded circuit. The outlet must be labeled according to NEC however stating that there is no equipment ground.

--
I'm never going to grow up.
Reply to
PeterD

y, I discovered some of the outlets are 2-prong, some properly-grounded 3-p= rong, and some 3-prong with no connection to the ground pin. =A0I have hear= d that GFCI outlets can be installed on 2-wire circuits, but does that help= any?

A GFCI detects imbalance in the currents in the 2 wires. If some current goes through you, it detects the imbalance and trips. They're a big safety improvement on 2 wire systems. Ungrounded circuits have been illegal for about half a century over here in Britain. Today we must use 3 wire circuits and GFCIs.

NT

Reply to
Tabby

discovered some of the outlets are 2-prong, some properly-grounded 3-prong, and some 3-prong with no connection to the ground pin. I have heard that GFCI outlets can be installed on 2-wire circuits, but does that help any?

It helps in two ways:

1) Safety. A properly working GFCI installed on an ungrounded, 2 wire circuit trips if some defect causes current > ~5mA to flow from line through your body to ground. For example, say you're using an old (ie not double insulated) power tool, and a defect in the tool causes the hot wire to contact the metal case of the tool. The GFCI will trip. At worst, you'll feel a "tingle". 2) Older two prong receptacles can be replaced with modern 3 prong receptacles if they are fed by a GFI protected circuit and marked as ungrounded. So, for example, you could install a ~$10.00 GFCI receptacle at the first location on a branch circuit, connect the "downstream" wires to the load side and replace the "downstream" two prong receptacles with three prong receptacles. That's a lot less work and money than re-wiring the whole circuit. Alternatively, you can install a GFI breaker in the panel to protect the branch circuit, but that costs more and uses up one additional spot on the neutral bus in the panel.

If equipment must be grounded for any reason other than safety, GFCI does not help.

Down the thread you mentioned a refrigerator in the garage on a GFCI. You want to keep things like fridges and sump pumps off of GFI protected circuits, and the code allows for that if you do it right. For the fridge, if you want it off the GFI circuit, you need to install a grounded circuit to a single receptacle that is not accessible without moving the fridge. The fridge must be the only thing plugged in to that receptacle. General use receptacles in the garage and outdoor receptacles require GFI protection. All that said, you might be better off with a fridge alarm that notifies you if the temperature gets too high.

Ed

Reply to
ehsjr

I still have a couple of rungs supplying out door lighting..

Jamie

Reply to
Jamie

discovered some of the outlets are 2-prong, some properly-grounded 3-prong, and some 3-prong with no connection to the ground pin. I have heard that GFCI outlets can be installed on 2-wire circuits, but does that help any?

Absolutely NO "grandfathering"??

Reply to
Robert Baer

y, I discovered some of the outlets are 2-prong, some properly-grounded 3-p= rong, and some 3-prong with no connection to the ground pin. =A0I have hear= d that GFCI outlets can be installed on 2-wire circuits, but does that help= any?

The result from replies here and elsewhere I posted this question is that a GFCI installed as a replacement in a 2-wire branch circuit is an improvement in safety, and is recognized as an acceptable replacement by the NEC

NEC 406.3(D) Replacements (3)Non-grounding type receptacles. (b) A non-grounding-type receptacle(s) shall be permitted to be replaced with a ground-fault circuit interrupter type of receptacle(s). These receptacles shall be marked "No Equipment Ground".

Followup question - there was a time (pre-1996, I believe) when it was NEC-legal to connect both the ground and neutral terminals of a three- prong receptacle to the neutral conductor in a 2-wire circuit. Is that better or worse than just leaving the ground disconnected and labeling it as such?

Reply to
Richard Henry

discovered some of the outlets are 2-prong, some properly-grounded 3-prong, and some 3-prong with no connection to the ground pin. I have heard that GFCI outlets can be installed on 2-wire circuits, but does that help any?

Worse. That energizes the yoke of the receptacle and the metal j-box through the impedance of whatever is connected. If the neutral is opened between the illegally "grounded" point and the service panel, there will be 120 volts on that yoke - and on the ground prong of the receptacle. The metal housing of your old power drill or whatever is plugged in could then be lethal.

Under the present NEC code, the service panel is the only place where neutral and ground are allowed to be connected, and that rule is there for safety.

In the case where an equipment grounding conductor *is* present, then that conductor _must_ be connected to the green ground screw on the receptacle, and to the j-box if it is metal. Examples of "equipment grounding conductors": the bare copper wire in romex cable; the metal sheath in armored cable; metal conduit. When those conductors are connected to the ground bus in the service panel, they are called equipment grounding conductors.

Ed

Reply to
ehsjr

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