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Range Cooker Connection Refusal.

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A lady today asked me to estimate to do some cooker circuit alterations in her house. She has an old electric range cooker in the kitchen which she is to replace with a new one rated at about 11.2kW.

 

A certain national electrical retailer would not connect up her new and paid for range cooker as the cooker supply is run in 10.00mm2 T&E and protected by a B50 M.C.B. plus R.C.D.

 

The reason given was that the supply is too big and will overload the new cooker.

 

The retailer insisted that the  B50 M.C.B. be replaced by a B40 M.C.B. and the final cooker connection from connection unit to cooker, be run in 6.0mm2, the 10.002 final connection being removed.

 

Comments please.

 

Z.

 

 

 

 

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    Chris Pearson: 
    I think that we can all see why a minimum size of MCB should be specified, but I am struggling to see why the maximum should be for a dedicated one appliance circuit. If the cooker specifies, say 40 A and 6 sqmm cable, but 50 A and 10 sqmm are used, the circuit cannot be overloaded. You could even use 6 sqmm cable on the 50 A MCB subject to the higher let-through energy of the larger MCB not being excessive - 433.3.1(ii).

    wallywombat:

    We don't know what rating the manufacturer has used for the terminals and the internal wires to them. If they've allowed for any diversity, then in the extreme case of, e.g. a hob used to continuously heat 4/5 pans of water because the boiler's broken and someone wants a bath, then we'd want a suitable CB to trip before the internals overheat.

    I don't think that is the correct approach, but I'd be interested to see what others think. If the cooker can draw more than 40 A after diversity, the OCPD needs to be > 40 A. It's Ib ≤ In, is it not? 433.1.1

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  • 0

    Chris Pearson: 
    I think that we can all see why a minimum size of MCB should be specified, but I am struggling to see why the maximum should be for a dedicated one appliance circuit. If the cooker specifies, say 40 A and 6 sqmm cable, but 50 A and 10 sqmm are used, the circuit cannot be overloaded. You could even use 6 sqmm cable on the 50 A MCB subject to the higher let-through energy of the larger MCB not being excessive - 433.3.1(ii).

    wallywombat:

    We don't know what rating the manufacturer has used for the terminals and the internal wires to them. If they've allowed for any diversity, then in the extreme case of, e.g. a hob used to continuously heat 4/5 pans of water because the boiler's broken and someone wants a bath, then we'd want a suitable CB to trip before the internals overheat.

    I don't think that is the correct approach, but I'd be interested to see what others think. If the cooker can draw more than 40 A after diversity, the OCPD needs to be > 40 A. It's Ib ≤ In, is it not? 433.1.1

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