Hi

After posting some questions about cable sizes on this forum a while ago, I
have finally got around to wiring in my new cooker and hob.

To summarise:

Old set up was a slot in cooker / ceramic hob (one unit) with a rating of
10.2 / 11.1kw at 230/240 Volts. This has run for the past six years with 6mm
cable and a 32 MCB.

New hob and oven rated at 5.4kw and 4.9kw respectively, so 10.3kw total
load.. So get the new stuff up and running at the command of SWMBO, I lashed
the wiring the two units with 6mm cable (could not get 4mm as suggested
here) into one cooker outlet plate, all the cables fitted relatively easily,
and then to the old slot in cooker isolator, then obviously back to the CU.
The old isolator was hanging in the next room behind the kitchen wall. OK so
this was a lash up, but no kids in the house and SWMBO was told not to touch
!!!. This worked OK no problems, no tripped MCB etc.

Then yesterday, I had finished the tiled slash back etc and fitted the new
45A isolator, one with a single 13A socket in. So wired the oven and hob via
the single cooker outlet plate as mentioned above to the new isolator, then
put in a new run of 6mm back to the CU. The old cable was too short. When I
turned the CU back on again there was a load deep electrical "pop" from the
CU and the cooker 32A MCB and the split load RCD had tripped.

So the wiring now looks like this. 32A MCB - 6mm - 45A DP Isolator (new) -
6mm - single cooker outlet plate - then two 6mm cables to oven and hob.

I have not dared try again and have a lecky my builder knows coming
tomorrow, but any other ideas folks. Is the above arrangement OK? Are the
cable sizes really OK?

Any advice gratefully received.

BTW I have been doing domestic electric as DIY for 20 years now and I have
never had this happen to me before, so I consider myself to be relatively
competent and work very methodically