What do the manufacturers' instructions say?

It may be a bit late now, but if the supply is limited to 32 A, why buy such a powerful hob?

Hi Chris. They don't say a lot!

https://www.bosch-home.co.uk/product-list/cooking-baking/hobs/induction-hobs/PIE631BB5E

Maybe I just don't know what I'm looking for, but it seems clear that the hob needs a 32a supply. But would you expect the instructions to tell you if it can share that supply with another appliance?

Two reasons for wanting a powerful hob really - wife is keen not to lose the power she had when cooking with gas, plus the kitchen company only had a choice of 32a or 13a and the latter doesn't look up to much. 

I'd say if it is easy to do either way then share it with the oven. Then there is a single method of isolation for cooking stuff, and not having to remember which one, or if the socket cct trips out when the washing machine, dryer and oven are on at once.

Your bigger problems are likely to relate to RCD protection, ideally you want a large induction appliance on its own RCBO, not sharing an RCD with much else - some designs are pretty close to using all the earth leakage allowance on their own.

My experience of high rated induction hobs is that it is almost impossible to reach anything like the full power rating, unless one is doing  a load test with pans of cold water on every ring and racing them all to the boil at once.

For normal cooking, the thing  is turned well down.

Sounds like a pretty typical 7.2kW induction hob - same as I have at home and mine's been running off a 20A RCBO for half a decade now without any trouble (including doing many a Christmas dinner for the extended family)

I reckon diversity is applicable pretty much as normal. Diversity isn't just about the chances of things being on at the same time, but also the length of time that they're on for - as from an overload perspective things take time to heat up (both cables and protective devices). 32A for 10 mins likely warms things up less than 20A for an hour. Induction hobs actually have an advantage there - since they only heat what needs heating they have very fast heat-up times (no waiting for 5 mins for the hob itself to warm up before you can start cooking properly like the old mineral insulated spiral types) and overall lower energy consumption means their "on" times will overall be less than a traditional hob.

The difficulty the manufacturers have is that across much of Europe you can't sensibly provide a simple 32A single phase circuit as their incoming supplies are often limited to 32A or 45A per phase - so things like this are usually supplied in effect by two 16A circuits (normally from different phases) which makes diversity much less helpful. Even if you apply the traditional UK calculation (100% of the first 10A and 30% of the remainder) to 16A you still end up with nearly 12A so will end up with a 16A circuit anyway once you pick the preferred size MCB. In some other areas where single phase supplies are common (but still with a low capacity) they might need to go for a 32A circuit but you'd be expected to add load shedding to remove some other heavy loads while the hob is in use. All in all I can understand why the manufacturers just provide the blandest possible information and leave it to local electricians to figure out what's needed in their particular locality.

   - Andy.

Is the oven a Bosch oven? Instructions say if oven make is not a Bosch, then a wooden partition is needed between them. But oddly no partition is needed if fitted above a drawer, I would have thought loose objects sticking up in the drawer could damage the cable.

Table 4D5 says 6mm T&E using reference method C is good for 47A, and the OSG says that 6mm with a 40A MCB is a supported combo for decent lengths of cable. So having both devices sharing the radial isn't going to tax the cable. And if you're worried about the breaker tripping during the first 15 minutes of cooking when everything is on at full and pans of water are heating up etc, then you could always replace the B32 with a B40, but I doubt that that would be needed.

Also mind that vast majority of manufacturers of induction hobs have in their instructions a warning for those persons with either a pacemaker or insulin pump that the electromagnetic waves may cause issues, so reccomendation is usually keep 600mm away from the appliance when its working.

So not just Diversity you need to consider, I know the risk may be negligable, but the right/wrong set of circumstances.

Cheers GTB. 

Thank you for that. As I read it, a 16 A supply is sufficient. Under "installation": "Power management options for 16A, 13A or 10A connection: limit the maximum power if needed (depends on fuse protection of electric installation)."

That would appear to take account of diversity. If you really were drawing 7.3 kW for any length of time, your kitchen would get pretty hot, unless it is very poorly insulated.

I'd put the cooker appliances on the same radial.

That requires either very long arms or a long spoon

GTB said:

reccomendation is usually keep 600mm away from the appliance when its working.

That requires either very long arms or a long spoon to stir the pot!

Thank you for looking. Just looking at the power management options myself. So it would appear that I can limit the maximum power in the settings. It appears I can go up in increments of 500w, so I could set it to 5000w to keep the total max load under 32a (oven says 13a but it's only 2kw).

I suppose that undermines the point of getting a powerful hob, so I think I'll leave it on full power, see if diversity let's me get away with it, and reduce the max powerful if I get tripping?