| Many older homes do not have grounding conductors in the older romex and are
wired with two prong receptacles. So what happens when you live in one of these
places and want to connect your computer and printers? It is hardly advisable
to cut the grounding terminal off the plugs and energize 3 to 4 thousand dollars
worth of equipment without a grounding conductor. Is there a way to accomplish
this task without moving out? The 1996 NEC contains a load of changes on
replacing a nongrounding-type receptacle, and we might as well repeat this
treatise here, just for old times sake. It says in 210-7(d) -now I hope you are
ready for this - because it is a mouthful - Replace a nongrounding-type
receptacle with a grounding-type if there is an equipment grounding conductor
available and connect the grounding conductor. If there is no equipment
grounding conductor then replace with a nongrounding-type receptacle or a GFCI
type that is marked "No Equipment Ground," or a grounding type if it
is protected by a GFCI and marked "GFCI Protected" and marked "No
Equipment Ground."
An equipment grounding conductor shall not be connected from the GFCI
receptacle that does not have an equipment grounding conductor to any other
outlet supplied by the GFCI receptacle, and an equipment grounding conductor
shall not be connected between grounding-type receptacles that are protected by
a GFCI type receptacle that has no equipment grounding conductor.
Got that! Good. And they wonder why electricians are paid so much. After
all this we still don't have a grounding conductor for our computer if there
isn't one available in the first place. But wait, all we have to do is go to
another Code making Panel and see what they have to say on this. Panel No. 2
writes Article 210, but Panel No. 5 writes Article 250. And in 250-50(a)and(b)
Exception it states, "For replacement of nongrounding-type receptacles with
grounding-type receptacles and for branch-circuit extensions only in existing
installations that do not have an equipment grounding conductor in the
branch-circuit, the grounding conductor of a grounding-type receptacle outlet
shall be permitted to be grounded to any accessible point on the grounding
electrode system as described in 250-81." And.... the 1996 Code will allow
this connection at any accessible point on the grounding electrode conductor.
So we can add a grounding-type receptacle to an existing system that does
not have an equipment grounding conductor and ground the grounding terminal to
the first 5 feet of water pipe that enters the building if this pipe is metal
and part of the grounding electrode, or connect it to any accessible point on
the grounding electrode conductor (after the 1996 NEC is adopted).
Now anyone knows, you just don't run a wire anymore without finding out all
the rules that apply. Installing this grounding wire is no exception. There
are rules on the color, the size, the correct wiring method, physical
protection, and even workmanship.
Let's start with the color. The NEC tells us in two places (310-12(b) and
250-57(b)) about the color of the grounding conductors. The grounding conductor
must be green, bare, or green with one or more yellow stripes with exceptions
for insulated conductors larger than No. 6 and conductors in multiconductor
cables.
Next, let's address size. The size is based on the overcurrent device
protecting the circuit. We use Table 250-95 for this. For a 15 ampere
overcurrent protective device a No. 14 copper or No. 12 aluminum conductor is
required. For a 20 ampere overcurrent device a No. 12 copper or No. 10 aluminum
conductor is required.
What about the wiring method? In general conductors must be run in cables
or raceways. Open conductors are allowed using several wiring methods such as
cable trays, concealed knob and tube, and open wiring on insulators. But none
of these would apply here. Exceptions have been made in several places to allow
the equipment grounding conductor for the grounding-type receptacle that has
been added to a circuit where no equipment grounding conductor is available to
be run separate from the other circuit conductors and to run by itself without a
cable or raceway. If you want to follow the Code on why this equipment
grounding conductor can be run separate from the circuit conductors go to
300-3(a) and (b) exception, then to 250-57(b) exception No. 3. To follow the
Code on why this conductor can be run by itself without a cable or raceway go to
250-92(c)(2) and the exception.
To summarize what we have so far: For a 15 or 20 ampere circuit we can run
a No. 12 copper that is bare or green or green with one or more yellow stripes
by itself so as not to be subject to physical damage from the receptacle
grounding terminal to the grounding electrode as described in 250-81 or, after
the 1996 NEC is adopted, to any accessible point on the grounding electrode
grounding conductor . We can also use a No. 10 aluminum equipment grounding
conductor with some restrictions found in 250-92(a). One restriction is where
used outside aluminum grounding conductors cannot be installed within 18 inches
of the earth.
Next, we have workmanship. Section 110-12 of the NEC requires that
electrical work be performed in a neat and workmanlike manner. There are so
many different types of construction that it is difficult to give any precise
instructions on how to do a neat and workmanlike job. This is where the
experienced electrician has to judge for himself on how to make the job look
neat. For some jobs this would require that the grounding conductor be
concealed inside the residence or office. This can be accomplished in some
cases by installing it behind mop boards in grooves, by fishing inside of walls
to a hole drilled in the receptacle box, and by stapling along basement trusses.
But each installation must be evaluated in the field to insure that the
completed job is neat and workmanlike and meets the customer's satisfaction.
There is one question that remains. We titled this article, "How to
Ground a Nongrounding-Type Receptacle." But we really didn't tell you how
to do that. Anyone knows you can't ground a nongrounding-type receptacle.
If you are not up to doing all this work, there are provisons in the the 1996 National Electrical Code for simply replacing a nongrounding-type receptacle with a GFCI type receptacle that provides additional safety. To see how to do this go the 1996 NEC change illustration by clicking here. You will have to use your back button to get back to here. |
