"405 TD Estate" wrote in message
oups.com...
On 18 May, 12:36, The Natural Philosopher wrote:
405 TD Estate wrote:
On a more serious note I need to put a shaving socket in the bathroom
- I assume this is just a straight 240v supply to the socket?

Yes, but the socket itself contains an isolation transformer.

Aah OK So that limits potential current right... yet voltage is still
at 240.

I have read in several places that it takes only a few milliamps to
kill you and it is the voltage which is required to start using your
body as a short so how is this safer? It's a question i'm not having a
go or anything.

Put it this way if I had to touch either a 12v car battery with 300A
available or 240v with (say) 1/2 A available in a wet bathroom I know
which i'd go for (12v!)

The transformer also serves to isolate the mains voltage from earth so if
there is a single pole fault then current can't return through you to any
nearby pipes/radiators. You correctly mention that the transformer does
limit current and a typical rating of 15VA does serve to reduce danger but
by reducing the energy hazard which is mainly prevention from burns as
something overheats. The main concerns with a car battery are the potential
to cause massive heat in the event of a short. There's always the
interesting danger of hot acid when the battery itself overheats.

50mA is enough to cause irreparable tissue damage with 100mA being almost
always fatal. Any major shock can cause a heart to stop but consider the
difference between AC and DC. A muscle spasm caused by DC will remain in
place until the current is removed and it's the long times involved that can
cause horrific harm (cooking flesh). An AC shock at UK mains frequencies
will cause muscle spasm but one that has the cause removed after 10ms (or
less) as the polarity changes and there's the chance to react and pull back
from contact.

Sorry for the rather serious email. I'd much rather the shower conversion
was a piece of DIY and candidate for an upcoming Darwin award.

Stuart