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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
  • Diversity should not be applied to circuits supplying individual appliances to select the supply cable. The cable should be sized in accordance with the manufacturers instructions or the plated rating. Diversity factors should be used for distribution circuits or the whole installation. Yes I know that the OSG says something that reads differently but I would not mind betting that will change in the next edition.

    That sounds like a retrograde step to me. The 30% after 10A rule for a final circuit feeding a domestic cooking appliance has been in existance since at least the 15th Ed (it was actually part of the regs in those days - table 4A) - so has certainly stood the test of time. Most of the manufacturer's installation instructions I've see don't give any advice about diversity at all - just vague requirements for a "suitable" circuit, "according to national wiring rules" (which is understandable as the methods of connection varies greatly from nation to nation - some would use a 2 or 3-phase 16A circuit, rather than everything on a single phase as we do). If the suggestion is that we can't use the cooker diversity rule for the final circuit, but can for a distribution circuit that feeds it, you can end up in the situation where the distribution circuit can have a lower rating than the final circuit it supplies - which would invite ridicule to say the least.


       - Andy.
Reply
  • Diversity should not be applied to circuits supplying individual appliances to select the supply cable. The cable should be sized in accordance with the manufacturers instructions or the plated rating. Diversity factors should be used for distribution circuits or the whole installation. Yes I know that the OSG says something that reads differently but I would not mind betting that will change in the next edition.

    That sounds like a retrograde step to me. The 30% after 10A rule for a final circuit feeding a domestic cooking appliance has been in existance since at least the 15th Ed (it was actually part of the regs in those days - table 4A) - so has certainly stood the test of time. Most of the manufacturer's installation instructions I've see don't give any advice about diversity at all - just vague requirements for a "suitable" circuit, "according to national wiring rules" (which is understandable as the methods of connection varies greatly from nation to nation - some would use a 2 or 3-phase 16A circuit, rather than everything on a single phase as we do). If the suggestion is that we can't use the cooker diversity rule for the final circuit, but can for a distribution circuit that feeds it, you can end up in the situation where the distribution circuit can have a lower rating than the final circuit it supplies - which would invite ridicule to say the least.


       - Andy.
Children
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