On Mon, 9 Aug 2004 21:28:10 +0000 (UTC), "Rick Hughes"
strung together this:

Agreeed 100%, but it's the leaqkage that causes the nusianace trips I would
assume.

Only if the leakage is not about to cause a fire\damage to equiopment
etc... If it goes off for a reason, i.e. a fault, then it's not a
nuisance trip. If it goes off for no apparent reason then it is a
nuisance trip.

instance a cooker element develops some leakage between the element
casing then some current will flow to earth and if that current is
greater than the tripping unbalance current then off the trip will go.

So my question on whether to protect a cooker is a valid one?

Yes, as is any question that involves the words "shall I RCD protect
my"?
In your case, it may or may not be neccesary to install an RCD on the
cooker circuit, if it does require one then that's your answer, if it
doesn't require one then you can fit one if you want some additional
protection.

If I didn't have an RCD on the cct ..... when would I have found the fault
? when it burst into flames ?

No, it would probably have never done anything at all. If you are on
PME, (which I seem to think you are), then neutral and earth are
connected together in the service cutout, and that hasn't burst into
flames has it?
Having the neutral and earth connected together throughout the house
on a PME system would never cause any problems whatsoever.
--

SJW
A.C.S. Ltd