On Sat, 5 Apr 2008 18:51:54 UTC, "spamlet"
wrote:

Also light circuit RCD always trips when a light bulb goes, but main also
trips if the light's earth is touched when removing lamp holders even when
the lighting RCD is 'off'?

Do you mean RCD or MCB? I guess RCD as you mention touching the earth.
RCDs will trip if neutral / earth are accidentally connected. There is
usually enough voltage.

The basis of an RCD is a current transformer carrying both live and
neutral conductors. If there is a difference in current, sufficient
voltage is developed to trip the circuit. There is little that can go
wrong with the sensor but the trip circuit can fail which is why they
should be tested regularly.

Check the circuits carefully before blaming the RCDs.

--
Jim Backus running OS/2 Warp 3 & 4, Debian Linux and Win98SE
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