23 Mar
2004
23 Mar
'04
10:51 a.m.
On Tuesday 23 March 2004 19:02, Tony Duell wrote:
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
--
Purdue University ITAP/RCS --- http://www.itap.purdue.edu/rcs/
The Computer Refuge --- http://computer-refuge.org
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).