24 Jun
2013
24 Jun
'13
4:51 a.m.
----- Original Message -----
From: "Tony Duell" <ard at p850ug1.demon.co.uk>
To: <cctalk at classiccmp.org>
Sent: Sunday, June 23, 2013 8:39 PM
Subject: Re: USB (Re: Next completely OT topic:)
And if you can run the workshop or work area through an RCD, maybe with a
sepperate circuit for things that dont like the power droppingg out , like
RK05's. You may also get the occasional niusance trip, like when you power
up a large rack, I need to turn on the 2 psu's of my 11/50 one at a time,
but this is a small price to pay for the extra safety.
BUT this is no substitute for probber earthing.
Dave
Generally, I don't worry too much about
3-wire equipment. I am
Nor do I, but I test the earth wire to carry twice the fuse current
(seriously). I want the fuse to fail first if there's a live-earth short.
particularly careful with old 2-wire stuff, such
as lamps with metal
bodies. There's it's not capacitor leakage that'll do you in, but the
accidental shorting of the body to the hot side of the line.
Sure.As far as I know, the rgulations here require metal lampholders to
be earthed, certainly all the good makes of them have earth terminals on
the lower shell.
We do ahve 'double insulated' equipment which only need a 2 wire cable,
Basically, there are various requirments 9the common way to meet them is
by having 3 insualtion devices, hense the neame) so that there is no way
an exposed metal part can become live. A lot of stuff is now
double-insualted, and I suppose it's safer if you are dealing with idiots
who don't bother to conenct, let alone chack, the earth wire, but I still
prefer a metal case, porperly earthed.
It's happened to me with brand-new lamps right from the store. I don't
understand why 2-wire lamp cord is still legal in these days of grounded
outlets being almost universal.
There si, AFAIK, onlt one typoe of device that can be legally sold over
here that is single-insulated and 2 wire. (OK, components don't count,
you can buy mans transformers with exposed mains terminals, it is assumed
they are a component and that they have to be fitted inside a suitable
case). The product in question? Decorative lights (like christmas tree
lights).
I guess I should pop open that PSU today and see what's going on.
Yes. It is betttttterto find out now, before the insulation breaks down
or somethign and the cae becomes solidly live. THat is not pleasant.
As for testing, _Ecvertyhing_ here gets meggered and if appropriate the
earth wire tested. Adn a full visual inspection. FWIW, all my classic
computers hav passed such tests with no problems. Some modern things have
not.
-tony