Tom MacIntyre writes:

On 25 Dec 2004 13:13:59 -0500, Sam Goldwasser
wrote:

Tom MacIntyre writes:

On 20 Dec 2004 20:52:48 -0500, Sam Goldwasser
wrote:

Thomas writes:

Can anybody help me with this problem?

snip

In a couple of days' time I am going to visit the apartment with a
socket-tester - it's a small plug which shows if the socket is wired
correctly. The only thing I can think of which might have caused the
death of three computers (if, in fact, they DID really die) is that the
"live" and the "neutral" wires to the socket (from the fuseboard) might
have been attached to the socket the wrong way round.

If this is the case, I know this wouldn't injure a lightbulb, but my
question is: would this injure a computer? A friend tells me that
current is "alternating" and that it therefore shouldn't matter whether
the live and neural wires to the socket are reversed. But does this
situation ring any bells with anyone?

Or is the guy in my apartment either just someone who has bought three
faulty computers in a row or someone who is just trying to take me for a
ride?

Reversed Hot and Neutral should not damage computers or any other modern
electronics or appliances, nor is it an inherently unsafe condition.
Anything that plugs into the wall must be designed to be safe if H and N
are reversed.

In isolation yes, but all bets may be off if they connect to another
device which is connected to a correctly phased plug. Been there, got
the T-shirt, saw the lights dim, and smelled the smoke. :-)

No, not true with anything less than maybe 75 years old.

Sorry, Sam, you should've really paid attention to the "been there"
part...I have had a situation like this arise, and within the past 25
years, with fairly new (at the time) equipment. While attaching a
video cable between 2 pieces of Telidon equipment in 1983, the lights
dimmed, a growling noise occured, and smoke emanated from one of the
units. A meter check revealed that one plug was wired in reverse.

Heck, all you have to do is defeat the capacitor in line with the F
connector on a modern TV set and you'll pop the fuse.

A disturbing aside...I once spoke to an electrician and told him this
story...he said that it didn't matter whether the plug was installed
ground over or under on an AC receptacle, the hot and neutral always
had to each go on the same side. And they don't want us wiring our own
houses...

What I said is that equipment must be designed such that this shouldn't
happen, not that a fault couldn't result in the situation you describe.

So, I should have perhaps been more explicit and said 'designed and
manufactured'.

No user accessible part should be connected to H or N directly or via a
low enough impedance to result in an unsafe fault current.

And, not just a plug with reverse H and N - that should still not cause
this. Yes, capacitors can fail. Wires can break loose and short.

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Tom


Granted, when isolated devices are involved, there really shouldn't be
a problem, and nowadays that is usually the case.

Should always be the case unless you have antique radios or something
like that.