Thomas D. Horne, FF EMT wrote:
wrote:
RBM (remove this) wrote:
The first thing you should do is verify that there is no ground. If the
cable is metal, that would serve as ground and you can buy ground wires to
connect to the box and receptacle or self grounding outlets


exactly, upgrading to 3 prong is easy if metal cable like BX or conduit
was run in the first place.

you might also ask your neighbors, who have likely been thru this.

to protect computer a UPS is prefered, be sure to run phone and modem
thru UPS.


A word of caution. If the cable is actually "BX", which is the cable
first manufactured at General Electric's Bronx plant, then the jacket
will not serve as an effective Equipment Grounding Conductor. Since
"BX" cable has an unbonded spiral metal tape jacket it does not provide
a low impedance pathway for fault current to return to it's source. The
resistance of the unbonded spiral metal tape jacket can be very high
which would allow a fault to continue without opening the circuits Over
Current Protective Device (OCPD). The installation of a GFCI at the
panel supplying the circuit can mitigate that condition because the
jacket will probably be able to carry the six milliamperes that it takes
to trip a GFCI.

Didn't know that....
I usually see an uninsulated wire sticking out of the BX cable whenever
I crack open the box, which is generally tucked into the clamp, I
assume that's a ground conductor for a Good Ground. Yes?


The installation of a Transient Voltage Surge Suppressor at the source
of the circuit is the best way to protect such a circuit against spikes
and surges. Make sure that the TVSS you install provides single point
protection to the power and any other wired utility that is connected to
the equipment your trying to protect. In order to keep the TVSS from
taking a continuous beating and failing prematurely you will need to
insure that the grounding electrodes for the power, telephone, cable,
and any antennas are effectively bonded together in order to serve as a
single grounding electrode system. Having the different grounding
electrodes behave as a single system is far more important than the
actual impedance to ground of the grounding electrode system.
--
Tom Horne

Well we aren't no thin blue heroes and yet we aren't no blackguards to.
We're just working men and woman most remarkable like you.