"Stefek Zaba" wrote
| >>Doesn't he mean he "...switch neutrals as well" (ie, use a DP switch)?
| > Well, that is a possibility I suppose...
| But not really in a lighting circuit, however.
The exception would be to an extractor fan (which if it's a timer over run
model will require a triple pole fan isolator for live / switched live /
I have another exception. I have a wall lamp in the porch, fed from a
hole drilled through from a disused back-box. Many moons ago I wired a
feed into the back-box from a loop-in from the living-room light. It
was convenient to use a two pole switch here, really as a handy way to
extend the neutral into the porch.
It was a shot in the dark drilling the hole from the switch position
at an angle of some 45 degrees, with a two-foot long masonry bit. As
it happened it came through at just the desired point in the porch!
Your friend is a true friend. Your friend is on your side. Your friend
wants to see you live to a ripe old age.
The 'somewhere' you read was the work of the Devil. The Devil wants you
to fry. The Devil is making you imagine you read this lunatic idea of
switching the neutral.
Back in the realms of the rational... the neutral is firmly connected to
earth potential; under no-fault conditions the neutral is 'safe' (won't
do you harm if you touch it alone, while in contact with the mass of
earth). By contrast, the live side is doing rapid oscillations, 50 times
a second, shooting up to something like 340V above earth potential,
sinking increasingly quickly down to earth potential, dropping past it
just as fast as it came towards it, ending up at something like 340V
below earth potential, and zooming back up again through 0V back to the
That's something you don't want to be touching - say, if you're clumsy
enough to touch the pin in the lampholder that's connected to the live.
Ow. That would give you an unpleasant tingle; or, if you were resting
against an earthed surface like the kitchen sink, kill you. Oops.
Hence, we switch the *live* side. That way, when it's off, it's *off*,
unlikely to hurt (or kill) us.
If we're smart, we don't go sticking our fingers into something that
alleged to be switched off, mind: it's always possible that someone was
listening to the Devil when they wired up their lighting... or that
someone under the Devil's influence swapped over the red and black wires
(brown and blue in the Modern world) somewhere further back in the
circuit, and the Devil made them forget to independently test that the
red (brown) wire really was the Live one and the black (blue) one Neutral.
It's not even funny. Switches go on the live side.
It's so not funny that many of the regulars will suspect your posting is
a fake to encourage the NICEIC profit-making myth that d-i-y'ers are all
too incompetent to touch their house electrics - a myth whose complement
is rapidly dispelled by spending a little time spent browsing the IEE
Forum where the pros gather... but I digress.
Switches go in the LIVE side.
That should really read;
All single pole switches should go in the live (phase) conductor only.
In answer to your query, all fixed equipment requires double pole
isolation. Lightswitches are for functional switching and single pole
switching should be in the live (phase) conductor *ONLY*.
Please reply to group or use 'usenet' in email subject
Thanks, but as I said lurch pre-empted (rather than prompted) my
question, I could see why you'd need to isolate the permanent and
switched lives, but not why you'd need to isolate the neutral.
Actually I still do wonder *why* (apart from "them is the rules") I mean
a ceiling rose is fixed wiring and you can't individually isolate
neutral from that ... so why is it deemed necessary to do so on fixed
equipment such as the fan?
What if some twerp has reversed the positive and neutral connections at some
point further back in the circuit ?...
With 'portable appliances' you can isolate them by pulling the plug out -
not so with fixed appliances IYSWIM.
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