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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.
  • 0
    I get it, but I am a compulsive worrier! The cagey remarks from the manufacturer about not using a cooker switch with an integral socket outlet (which the present one has) had me doubting. I began to wonder if the old method still applied in the same way to ceramic and inductive heating methods as it did to purely resistive ones and that I was missing something. A rating is a rating, but the nature of the loads are different?

    I'll most likely stick a 40A mcb in to cover it and see how it behaves.
  • 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.
  • 0
    Andy,

    Just been looking again. The model looks to be a different one to that.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?
  • 0
    What's the worry? -  a classic 32A circuit should be good for a domestic cooker up to around 19kW f.l. rating (presuming no socket on the CCU).


    Is this the one http://www.rangemaster.co.uk/products/range-cookers/classic/classic-90-induction? (or similar enough)


    The spec says 7.4kW total for the hob, 2.3kW for the grill, I can't see a rating for the oven, but let's say they're not more than 3kW each (for two of them) - so that's still only 15.7kW.


       - Andy.
  • 0
    I agree - hence my doubts.

    The unit is 2nd hand and no paperwork came with it apparently. Not sure now if the hob bit is ceramic or induction. The model does not seem to come up on Rangemaster's website.so it must have been superceeded.

    All I do know for sure is that it is a 900mm model and is all-electric.
  • 0
    I would be a bit doubtful about telephone advice that is not part of the written instructions.

    I would be inclined to use cable and MCB size as recommended in the written instructions, if these are not to hand, they should be obtainable on line.

    A smaller cable than recommended  if correctly protected by an MCB should not be dangerous but does of course carry the risk of nuisance tripping under heavy use of the cooker.

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