"Peter Parry" wrote in message
news
On Fri, 22 Apr 2005 15:50:09 +0100, "Michael Chare"
wrote:


What brand of Hob?

I have a Bosch induction hob which failed when new. When the Bosch engineer
was
working on the upside down hob to repair it he got a shock touching some part
you would not expect to be live. We measured the voltage with his digital
voltmeter and got a reading of about 80v (or so). In normal operation the
metal
bottom of the hob would have earthed the internal part that he touched. Not
having an RCD I live in happy ignorance of any currents that may be leaking
to
earth.

All induction hobs (and any other piece of equipment using the usual
noise filters) will put "earthed" components at half mains potential
if the earth is disconnected. This is not a fault but a perfectly
normal characteristic (and why Sect 607 earthing should be considered
in houses). The current will not be enough to kill or directly cause
injury but can cause indirect harm by causing you to fall off
ladders, drop things etc.

Yes, in this case the appliance was correctly earthed. The problem for the
repair man was that the bottom plate formed part of the earth circuit. A better
design would have ensured that the internal compnents were earthed even with the
bottom plate removed.
(Atleast that is how it appears, I have not studied it in detail)

--

Michael Chare