"Andy Wade" wrote in message
...
Sparks wrote:

Just checking it's not just me, but I think my new induction hob is
faulty!!
[...]
If I measure the current between its earth wire and Neutral, I am getting
about 2.9A

That's a bit ambiguous - do you mean the current that flows through your
meter with the meter leads connected between the neutral and earth
terminals, with the earth connected? (Or if not, then what exactly?) A
neutral-earth s/c current measurement like that isn't very helpful - what
you need to do is to measure the current in the earth wire of the
appliance. IOW connect the earth wire from the hob to the earth terminal
of the cooker connection unit via your meter.

Yep, this is exactly what I did Disconnected the earth from the connection
plate, then clipped one test lead to it, and the other the Neutral in the
connection plate (as connecting it to the earth in the plate trips the RCD)
I also tried clipping the test lead to the metal body of the hob and the
neutral in the connection plate - both displayed the same results of 2.9A
flowing (The test lead produces small sparks when connected too)

Make sure the appliance metalwork is floating, i.e. isn't connected to
earth through any other path. Now what earth leakage reading do you get?
Anything more than a couple of milliamps is a cause for concern.

Hob is sitting on a granite worktop, and the parts touching this are plastic
anyway so is isolated pretty well!

If I measure the voltage, it is about 120v

Strongly suggestive of a mains filter (RFI filter) and perfectly normal.

****

What (if anything) do the instructions for the hob say about earth leakage
current and compatibility with RCDs?

Nothing!

There is certainly no need for an appliance like this to be RCD protected,
and there's no advantage in it being so (TT-earthed installations
excepted). But that said, the leakage from a single healthy domestic
appliance should not be anywhere near high enough to trip a 30 mA RCD.

Sparks (who wants to RCD everything possible, now more than ever!)

Why?

Because if the hob is faulty, as I expect it is, this fault would not have
been identified as the leakage would not trip the 32A MCB - Say at some
point the earth gets disconnected for whatever reason - the chassis of this
hob will be ready to supply a user with 2.9A @ 120v - and as it is only
leaking 2.9A no protection device would trip.
Not only this, but I would be wasting nearly 350w of power 24/7!
(That's 8.4KWh per day or 3068KWh per year (That's nearly £250 per year
leakage!!)

Surely it has to be safer to provide more protection than is actually
needed?
(If not, please tell me why!!)

Sparks...