"John Rumm" wrote in message
...
Sparks wrote:

a RCD in many cases. What sort of earthing do you have?


TN-S


What you need to do is leave the live connected to the live, neutral to
the neutral, and then disconnect the earth. Now connect one test lead to
the earth connector on the appliance, and the other one to the earth wire
you just disconnected.


That will trip the RCD, as the leakage is a lot more then 30mA

In which case can you move the supply to the non RCD side of the CU and
repeat the test?

I havent tried this, as I felt it was pointless due to the results of mu
tests
I can do this is it is really necassary, however it will be a bit of a mare
to do!

As this method trips the RCD, I connected the probe the the Nuteral, as
it is at the same potential as earth

Your Neutral is very unlikely to be the *same* potential as earth - close
certainly, but given they are both going to be low impedance paths there
is a good chance a substantial current will be able to flow between them
if connected.

If it is faulty, then passing 2.9A to earth would be a rather odd fault.
I expect you are simply measuring a large current flow between N and E


Well, sort of - the disconnected earth of the hob and the N of the
supply.

So that measurement is taken with the hob effectively not earthed at all
(i.e. the earth wire from the supply cable was not connected to anything)?

Correct - The hob was placed on the granite worktop, with only plastic parts
of the hob touching this worktop, so the appliance was not earthed for this
test.


If you diconnect the hob and measure the resistance between L & E and E &
N and L & N (with all the switches/controls on the hob turned off), what
readings do you get?

Not Quite as simple as this, as it has electronic touch controls, not knobs
or switched - however the readings a -

L-E - Starts at about 11Meg - then rapidly climbs to infinity
N-E - Ditto above
L-N - Starts at about 4.5meg, and settles at about 1.4meg


Sparks...