|
|
|
|
RCD trips while working on dead circuit
wrote in message ...
Probably bad practice, but when I'm working on the wiring in my house,
rather than switching off the entire supply and incurring the wrath of
family who apparently can't function without electricity, I tend to
just switch off the circuit I'm working on.
The above explanation shows you one reason why relying on the MCB alone
for isolation is less than best practice. You'd do better to switch off
the whole supply, physically remove the L and N conductors from the MCB
and the N busbar respectively - put the bare ends out of harm's way into
a bit of connector block, or for best paranoia into spare ways in the
earth block. Then you can restore power to the rest of the installation,
and work at leisure on the properly-isolated (or even earthed) final circuit
you just disconnected.
The cautious among us when first working on a circuit we haven't
installed ourselves might even measure the voltage from the allegedly
isolated N and L conductors to earth before grounding them, and/or do
the temporary-connection-to-earth through a low-value glass fuse (so
you could see it blow) or an incandescent bulb (so you could see it
glow) Just In Case some eejut has cross-wired the final circuits; but
that's taking caution a bit too far, IMHO. Me, I isolate the Ns and Ls,
put them into free-waving terminal block, and then test AGAIN at the
working position that there is no voltage between earth and the allegedly
isolated Ls and Ns. 'Course, if you use a digital multimeter, you can
be misled by very-low-current induced voltages - connecting a suitable
resistance in parallel with the meter will soon sort out the difference
between a tiny capactively-and-or-inductively coupled current, and a
Nasty cross-connection.
Thanks to everyone for the explanation.
So... if I was to switch off just the circuit I want to work on, THEN
confirm with a meter that there is no voltage across the N, L and E
conductors... under what circumstances could that still put me at
risk?
David
|