Yeah this is absolutely the proper solution and all the proper reasons are
in here.

Purchase the transformer and you won't end up as Foreign Toast.


"Andrew Mayo" wrote in message
om...
(Taylor Miller) wrote in message
. com...

STOP!......

I've read this thread in its entirety and I have to say that grounding
an ungrounded two-pin system is potentially *more* dangerous than
leaving it the way it is.

Normally the neutral is, as has been pointed out by other posters
here, bonded to ground at the switchboard. Nominally this should mean
that all plumbing etc will then be at ground potential, and
furthermore, in a three pin system, that if an appliance fails
internally, the resulting short will blow the fuse or circuit breaker
rather than leave the case live.

If you have a three pin system, then the case of any appliance that is
not double insulated (i.e has no possibility of developing a short
internally that would leave the case live), will be connected to the
earth pin and thence back to the switchboard to be bonded to neutral.

But with a two pin system you do *not* want the neutral to be bonded
to the case. This is because there's a pretty good chance you'll plug
such an appliance into a socket where line and neutral have been
reversed. With three pin sockets, doing this will not have any nasty
consequences because, remember, the earth pin is still connected to
the appliance case. But plugging in an appliance where the case is
connected to neutral into a reversed two-pin socket puts the whole
case at line potential.

Now reach over and touch that radiator!. Bam!.

This is why all the earth wires were cut in that expensive equipment.
That way the case floats. You can still get a shock; the zap comes
from capacitive coupling rather than a direct link - but if you plug
the gear into a wrongly-wired socket, you won't put the case at line
potential.

Also, if the neutral is allowed to float, then although there will be
a path from any plumbing back to neutral, this will be through a fair
amount of dirt rather than via a wire. So, (and given that Mexico is a
fairly dry place, most of the time) the amount of current that can
flow is limited by this.

If you want to run audio gear in an environment like this, use a large
isolating transformer (e.g 1 or 2KVA) and run everything off the
secondary of this. No matter what, you are now completely safe because
neither side of the secondary has a potential relative to ground,
because the transformer insulation prevents any direct connection (do
NOT use an auto-transformer, it MUST have an isolated secondary). You
see this used in bathrooms; the little shaver socket is powered from a
small isolating transformer so that no matter what, you can't get
zapped unless somehow you get across the entire secondary.

Now you can use normal three pin sockets and run the third pin back to
your ground outside. The line and neutral go to the secondary of the
transformer. There is now no interaction at ALL with the un-isolated 2
pin sockets in the rest of the house.

A 1KVA transformer will probably cost a couple of hundred bucks which
is cheap insurance, unless you don't value your life.

PS: with a three pin system there are six ways you can wire a socket,
of which only one is correct. However, if you work it out, there's
only two ways to wire a socket where the case is wrongly connected to
line AC. One of these will promptly blow the fuse, and in the other
case, the appliance won't power up, which *hopefully* will alert the
potential victim before its too late.

Whereas with two wires, if you get it wrong, the appliance will work
but the case will be live.