I want to replace an existing 2-prong receptacle in a bathroom with a GFCI
receptacle. There is no ground wire going to the existing receptacle and no
grounded metal cable or grounded metal outlet box -- just two separate
wires, one white and one black. There is also no practical way to run a new
ground wire back to the service.
In this situation, is it okay to go ahead and install the GFCI receptacle
and put the sticker on it that says "No Equipment Ground"?
UP.SO. I "could" run a ground wire from the GFCI receptacle to a cold water
pipe and make sure that there is a jumper across the hot water tank in and
out pipes and across the water meter. But, I think I read somewhere about
that being a bad idea (using the cold water pipe for a ground). That is a
bad idea, right?
Use GFCI because it operates on the 'difference' in current between
live and neutral. If someone did get a contact or drop the hair dryer
in the wet metal bath tub any conseuent current likely to trip the
Yes, as I understand it (I haven't tried it). I believe the TEST
button in the receptacle allows a small current to pass from the LINE
side hot to the LOAD side hot around the current transformer, thereby
creating the imbalance that should trip the GFCI. In contrast a
plug-in tester will not work, as it relies on the ground connection.
A GFCI will indeed work properly and to specs without a ground. Go read how
they work and why/when they trip. Every box and most sites tell you what to
do when there is no third wire. The OP had it right. Earth is NOT used in
the operation of the GFCI.
or if you're Canadian
Google is full of good information
Newsgroups are great places to get assistance.
Absolute nonsense, as GFIs measure only the imbalance of currents in
the hot and neutral lines that pass through their current sensing
transformers. No GFI can require an earth ground for proper
operation and still meet UL standards.
The test button merely connects the hot to the GFCI's ground
reference, so no earth ground is needed to test operation. But a plug-
in GFCI tester will work, whether or not the GFCI is earthed.
Here's National's document for their old LM1851 GFCI chip:
Right except it is line side hot to load side neutral (or vice versa).
Nope. The GFCI outlet circuit makes no connection to "ground". The test
button connects a resistor from the hot wire ahead of the current
transformer to the neutral downstream from the current transformer (or
vice versa) resulting in a current through the transformer only on the
A plug-in tester connects a resistor from hot to ground. Since ground is
not connected to anything a plug-in tester will not work.
Interesting that the circuit (fig 2) does not show the test button that
is on all GFCIs.
Also interesting that the feature that causes an immediate trip if there
is a downstream N-G connection only adds 2 parts.
But I've tried it with a Hubbel (Shock Shield 3-outlet) plug-in GFI
with its ground prong retracted and a Sears branded Leviton wall
outlet GFI connected to the AC through a 2-wire cheater cord. I
believe both used General Instruments GFI chips.
BTW...not only is it OK to (and you should) replace the ungrounded
bathroom receptacle with a GFCI, it is also code compliant to replace
any 2 prong, ungrounded receptacle with a 3 pronged receptacle as long
as that receptacle is protected by a GFCI and marked as having No
For example, if you have a circuit full of daisy chained 2 pronged,
ungrounded receptacles, replace the first one in the circuit with a
GFCI and wire all the downstream 3 prong, yet still ungrounded
receptacles off of the load side.
It's a fairly common practice and allows for the use of three pronged
cords in "older" homes.
NO, it does NOT "allow" use of 3-wire equipment!! If a 3-wire piece of
equipment is plugged into an outlet, the earth ground in that case DOES need
to be present. THAT is why the outlets must be labeled as having NO ground!
It's to prevent just that kind of accident waiting to happen.
Newsgroups are great places to get assistance.
Perhaps we need some clarification here.
We are talking about people protection only. We're not discussing
whether the absence of a ground will be a detriment to the operation
of the equipment.
It is my understanding that the GFCI will protect the user should
there be current leakage to ground within the device.
If there is any type of short to ground within the device then there
will be a differential between the current on the hot and the current
on neutral and the GFCI will trip and the user will be protected.
Why else would the NEC allow for the use of a 3 prong outlet on an
ungrounded circuit if they didn't expect you plug a 3 prong cord into
You'll note that code says it must be labeled as No Equipment Ground,
not simply No Ground.
For the safety of us all, I won't mind if you correct me.
Downstream outlets are also tagged "GFCI protected".
Avoid connecting the outlet grounds together on downstream grounded
outlets where a ground is not present.
Seems like that should have been obvious to Twayne. If 3 wire plugs were
not allowed the NEC would require a 2 wire GFCI outlet - which it
doesn't. The NEC explicitly allows 'grounded outlet' GFCIs on 2 wire
circuits, and as you said above, allows the GFCI to protect conventional
grounded receptacles downstream.
Well, 406.3(B) of the 2008 NEC states: "Receptacles and cord
connectors that have equipment grounding conductor contacts shall have
those contacts connected to an equipment grounding conductor". And
406.3(D), the section that deals with using GFCIs on circuits without
equipment ground, does not appear to override 406.3(B). So I agree
the situation is confusing and the intent is not clear.
Set Lawyer-Speak Mode = True
A 3 prong plug is typically connected to a cord which has an equipment
grounding conductor within, therefore the "cord connector" portion of
406.3(B) is satisfied.
Once this cord is plugged into a 3 prong receptacle, the receptacle's
equipment grounding conductor contact will be connected to the cord's
equipment grounding conductor, this satisfiying the receptacle portion
of 406.3(B). Prior to the insertion of the plug, the grounding hole in
the receptacle is nothing more than an extra hole since it's not
attached to anything. If it's not attached to an equipment grounding
conductor, it isn't a equipment grounding conductor contact because
the code says it isn't.
Set Lawyer-Speak Mode = False
That clears it up, now, doesn't it?
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.