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Manufacterer's advice/instructions

whjohnson
Been asked to connect up a used rangemaster all-electric cooker. No rating plate but model name is 'classic 90'. It has an induction hob.

Existing cable is 6.00mm on a 32A mcb.

Phoned the manufacturer who said it would be fine, since diversity could be applied but we would have to fit a cooker switch without a built in 13a socket and uprate the mcb to 40A.

I am a little troubled to say the least.

Comments welcome.
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  • 0

    The closest rating I came up with was 14.74KW.

    Splitting hairs I know, but 6.0mm? Even with a 40A it's running close.to 65A?



    But there's a large amount of diversity for domestic cooking appliances. The usual rule (which goes back a couple of generations at least) is 100% of the first 10A and 30% of the remainder (plus 5A if the cooker circuit also supplies a socket). So your 65A (full load) only really needs a 26.5A circuit.


    Remember that a cable (and a fuse or thermal element of an MCB) will take time to heat up - shove 50A or 60A down a 6mm² cable starting from cold and it'll take several tens of minutes to warm up to 70 degrees - by which time the oven thermostat will have started switching the oven off every few minutes and the pans will have started to boil and been turned down to a simmer setting. The '10A and 30%' rule has been used successfully for probably hundreds of millions of Christmas dinners by now (plus countless everyday meals) and seems to have been perfectly satisfactory.


      - Andy.
Reply
  • 0

    The closest rating I came up with was 14.74KW.

    Splitting hairs I know, but 6.0mm? Even with a 40A it's running close.to 65A?



    But there's a large amount of diversity for domestic cooking appliances. The usual rule (which goes back a couple of generations at least) is 100% of the first 10A and 30% of the remainder (plus 5A if the cooker circuit also supplies a socket). So your 65A (full load) only really needs a 26.5A circuit.


    Remember that a cable (and a fuse or thermal element of an MCB) will take time to heat up - shove 50A or 60A down a 6mm² cable starting from cold and it'll take several tens of minutes to warm up to 70 degrees - by which time the oven thermostat will have started switching the oven off every few minutes and the pans will have started to boil and been turned down to a simmer setting. The '10A and 30%' rule has been used successfully for probably hundreds of millions of Christmas dinners by now (plus countless everyday meals) and seems to have been perfectly satisfactory.


      - Andy.
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Community Rules & Guidelines