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Induction Hob again

Former Community Member
Former Community Member
I hope that you don’t find me impudent but I am having difficulty finding an electrician to explain why they will not install the induction hob and double oven that we are looking to fit in our new kitchen.
We have chosen a hob 7.4 kW and oven 6.3 kW. The cooker radial circuit has 6mm2 cable with 40A MCB. The run is some 12 m. The house was built (converted) in 2002 and inspected last year (DPN18C). We cannot run an extra cable because the CU is separated from the kitchen without a horizontal floor or roof space and presumably runs the existing cable through the stud walls.
The kitchen fitting company electrician has visited but won’t carry out the work unless we sign an indemnity as it would invalidate our insurance and the appliance guarantee. He suggested instead two plug-in ovens which we could add to the ring main. I have contacted four other local electricians but they all use 13.7 kW means 59.7 A which means 10 mm cable and ignore my request to consider diversity.
Should I give up and accept the two oven solution or perhaps a gas oven?
Do you know of a way of finding someone who understands diversity?
Am I simply wrong?

Parents
  • A chunkier cable might be nice, but it sounds like there is no real risk, unless the 6mm cable has some other issue, like it changes colour from one end to the other - implying some unknown hidden joint, or the wall is full of insulation or worse some nasty plastic that reacts with PVC.

    handy cable rating tables

    (table-4d2a is a good starting point to see the dramatic effects of insulated walls versus free air..)

    So long as the breaker is such that  it protects the cable, nothing terrible will happen - as others have noted, you will fire the trip first, which may be a real pain in the wotsits in mid soufflé or whatever, but not actually dangerous is it.

    Do check the wall filling though as a 40A breaker would allow a 6mm cable in an insulated wall to be over-run quite a bit, which is not so good.

    Thinking about your sparks' advice, you may wonder if he has considered your company fuse rating  ? It may say  "100A" on the holder next to the meter, but a 60A or an 80A fuse in a 100A holder is quite common, and on a housing estate then there may be 20 or more similar houses on each 400A fuse at the substation end (or more like 50 per phase on a larger transformer) so if you took the sparks' advice at face value, you'd probably have to disable the shower and the sockets while cooking and liaise with the neighbours to wash on alternate days. In reality, such measures are not needed and do not happen.


    There are alternate hacks sometimes seen when it gets more desperate, like cables that pop outside and run along the wall for a bit, or multiple parallel runs, but in this case it seems a bit OTT.

    M.

Reply
  • A chunkier cable might be nice, but it sounds like there is no real risk, unless the 6mm cable has some other issue, like it changes colour from one end to the other - implying some unknown hidden joint, or the wall is full of insulation or worse some nasty plastic that reacts with PVC.

    handy cable rating tables

    (table-4d2a is a good starting point to see the dramatic effects of insulated walls versus free air..)

    So long as the breaker is such that  it protects the cable, nothing terrible will happen - as others have noted, you will fire the trip first, which may be a real pain in the wotsits in mid soufflé or whatever, but not actually dangerous is it.

    Do check the wall filling though as a 40A breaker would allow a 6mm cable in an insulated wall to be over-run quite a bit, which is not so good.

    Thinking about your sparks' advice, you may wonder if he has considered your company fuse rating  ? It may say  "100A" on the holder next to the meter, but a 60A or an 80A fuse in a 100A holder is quite common, and on a housing estate then there may be 20 or more similar houses on each 400A fuse at the substation end (or more like 50 per phase on a larger transformer) so if you took the sparks' advice at face value, you'd probably have to disable the shower and the sockets while cooking and liaise with the neighbours to wash on alternate days. In reality, such measures are not needed and do not happen.


    There are alternate hacks sometimes seen when it gets more desperate, like cables that pop outside and run along the wall for a bit, or multiple parallel runs, but in this case it seems a bit OTT.

    M.

Children
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