On 6/15/2007 12:16 PM, Gus Wirth wrote:
This isn't directly Linux related, but does pertain to computers that
run Linux.
I want to run some computers in the back room of my house, but because
my house was built in 1960 I don't have ground wires, only polarized two
prong sockets. I know that I could cheat and just skip the ground prong
connection on a new socket but I want to "do the right thing" and
actually have a grounded outlet for use with the computers.
I have several options for some of the sockets but not all. One is to
drill through the backside into the adjoining closet and run the wire up
from there. The other I thought of was to put ground wires behind the
baseboard and bring them up into the socket from there. I'm not sure how
an electrician would do it, probably go into the attic and drill down
into the wall. All the house wiring runs through the attic down to the
walls.
Has anyone had a wiring retrofit done? Any suggestions?
I have done some. As far as I know, the code still allows installing
GFCI outlets to get 3-prong compatibility without running a ground wire.
In fact, it if you replace the first outlet on a branch circuit with a
GFCI outlet, outlets downstream of the GFCI can be replaced with 3-prong
outlets without a ground wire. That's what the code allows (or did 8
years ago when I was up on it), but you might want to do it differently.
Some houses in the late 50s were wired with 2-prong outlets but had a
14-ga bare ground wire run nearly horizontal inside the walls taking the
shortest path to the breaker or fuse box. On stucco houses it ran
between the tar paper and the studs, along with the bailing wire to
support the tar paper. This was for a few years when grounding was
required but not 3-prong outlets. The ground wire did not enter inside
of the outlet boxes and was loosely wrapped around one of the outlet
screws, in between the ear of the outlet and the box. You might check
for that.
Consider what grounding outlets to to the circuit breaker panel is going
to do before going to a lot of trouble. In this dry climate the
resistance of an old corroded ground rod from the service entrance panel
to "ground" is likely 25 ohms or more. A lot of metal piping outside of
houses and under streets has been replaced with plastic. And dielectric
unions have been put in at water meters. On the power pole the
center-tap of the step-down transformer (the neutral run to your house)
is connected to a copper wire run down the pole and into the hole it is
planted in. Good enough for lightening protection, not a very low
resistance to ground.
So by running ground wires from the breaker panel to the outlets you're
connecting everything together but probably not to any real "ground".
The approach I have taken is to make sure the grounds of all my computer
stuff are connected together with 3-prong outlet strips, and put a GFCI
wherever I need a 3-prong outlet.
Karl
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