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.
Takoma Park Volunteer Fire Department Postmaster wrote:
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.
One other option to consider is to replace the outlet with a new 3 pin and
to put epoxy or some other similar substance into the ground hole. This
prevents anyone from using a 3 pin plug. And before I get a barrage of e
mails telling me this is is illegal etc, it is not. I have a safety
certificate from a hydro inspector who, discretely, suggested this and gave
me a full inspection on a property. Did I agree with it? The other options
were to leave old 2 pin outlets in this property that posed a bigger fire
risk due to age and bad contacts, or to re-wire, however that was not an
option, short term for me.
The GCFI oulet is the safest and best way to go if a 3 pin grounded
plug will be used.
Good luck whichever way you go.
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
That simply is not true. The US national electric code places heavy
restrictions on the use of flexible metallic conduit as an Equipment
Grounding Conductor (EGC). viz.
250.118 Types of Equipment Grounding Conductors.
The equipment grounding conductor run with or enclosing the circuit
conductors shall be one or more or a combination of the following:
(5) Flexible metal conduit where both the conduit and fittings are
listed for grounding.
(6) Listed flexible metal conduit that is not listed for grounding,
meeting all the following conditions:
a. The conduit is terminated in fittings listed for grounding.
b. The circuit conductors contained in the conduit are protected by over
current devices rated at 20 amperes or less.
c. The combined length of flexible metal conduit and flexible metallic
tubing and liquid tight flexible metal conduit in the same ground return
path does not exceed 1.8 m (6 ft).
d. The conduit is not installed for flexibility.
Most of the "Flex" that is available is not listed for grounding. The
pot metal fittings that are often used with flex are not listed for
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.