On Tuesday 23 March 2004 19:02, Tony Duell wrote:
> Are you saying that the main switch in your fuse box / consumer unit
> / breaker box / whatever you call the thing after the electricity
> meter in your house is a single pole device ? In the UK it is
No, it's double pole, but it breaks only "hot" wires, not the neutral.
In the US, we (normally) use a center-tapped power tranformer, with the
center grounded, and being connected as the "neutral" phase, giving
120V between hot and netural and 240V between the two hots. Of course,
there's also 3 phase, in the 208/102 wye, 240/120 delta, 480/277 wye,
and other variants. But, I've not yet seen any service that is just a
single hot + neutral. (I'd imagine that they might be used in "old"
houses/apartments.)
> _required_ to be a double pole one, breaking live and neutral (and
> for 3 phase star installations it's required to break all 3 phases
> and neutral).
On 3 phase wye (star) / delta, it's customary to just break the hot
phases.
> > Floating circuits are also no fun for electricians. Many have been
> > fooled (and zapped) when their wiggie lit (or did not light)
> > because one end was connected to a flaoting wire.
>
> The most common problem is that your neon tester will light on a
> disconnected wire due to capacitive coupling to a still live wire.
> This is a safe error, in that it says a wire is live when it's not.
> For the life of me I don't see how a totally isolated circuit can
> test dead on a neon tester but actually be live (in fact I don't see
> how it can be live at all if it's isolated on both live and neutral
> wires).
My guess would be a that a there's a live phase that's connected and the
other phase is isolated.... which is why you should always test phase
to ground, not phase to phase. Of course, I assume that the ground is
connected properly, which may not be a valid assumption; it wasn't
connected to some of the outlets in my last apartment!
Pat
--
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Received on Tue Mar 23 2004 - 18:51:40 GMT