Help an idiot out? Diversity and manufacturers' instructions.

[mat_12345]

Hi all, I'm getting a 32a induction hob and a 13a oven installed as part of a kitchen refurb.

The existing cooker circuit is 6mm protected by a 32a mcb.

After a long trawl through various forums I think the prevailing view is that this is fine to use this for both appliances, because of diversity. Unless this is contradicted in the manufacturer's instructions.

My daft question is - where would that be stated? I've looked through every doc here and although it says the hob needs 32a protection, there's nothing to suggest it could or couldn't share that protecion with another appliance.

Bosch PIE631BB5E 60cm Black Induction Hob

The induction equipment has fast heating elements, making it excellent for everything from frying, to quickly boiling water. With four cooking zones, a timer, and a touch control panel at the front, this will be an excellent addition to any culinary space. It also boasts many safety features...

www.howdens.com

Am I overthinking this? (I tend to worry!)

 

[pc1966]

For domestic cookers the usual assumption is 10A plus 40% of the remaining load, plus 5A if a socket is fitted. So 32A becomes 10 + 0.4 * (32 - 10) = 19A.

Provided the supply MCB matches the cable rating it should be fine. Even hammering all outputs at once is unlikely to trip it in less than a couple of minutes, and usually the heaters are cycling by then to set temperature.

 

[mat_12345]

For domestic cookers the usual assumption is 10A plus 40% of the remaining load, plus 5A if a socket is fitted. So 32A becomes 10 + 0.4 * (32 - 10) = 19A.

Provided the supply MCB matches the cable rating it should be fine. Even hammering all outputs at once is unlikely to trip it in less than a couple of minutes, and usually the heaters are cycling by then to set temperature.

Thank you. That seems like a sensible answer. I think I've over-researched this and found some people disagreeing about using diversity for induction hobs, which put doubt in my mind.

 

[pc1966]

Some induction hobs are electronically limited to take a maximum current, but the sum of all of the 'heaters' is actually more than that. I.e. they have enforced a form of diversity in terms of the rated supply already. For example, you might have 4 pan zones each rated at 3kW max = 12kW = 52A if all on, but the controller will limit the use to 32A, pulling back the power one some or all to meet that.

Again, the domestic use argument is few folks are going to put on 4 pans all at maximum at once anyway and keep doing so for long periods so the MCB becomes likely to trip. However, professional chefs cooking dozens of meals an evening do that sort of thing.

 

[mat_12345]

Some induction hobs are electronically limited to take a maximum current, but the sum of all of the 'heaters' is actually more than that. I.e. they have enforced a form of diversity in terms of the rated supply already. For example, you might have 4 pan zones each rated at 3kW max = 12kW = 52A if all on, but the controller will limit the use to 32A, pulling back the power one some or all to meet that.

Again, the domestic use argument is few folks are going to put on 4 pans all at maximum at once anyway and keep doing so for long periods so the MCB becomes likely to trip. However, professional chefs cooking dozens of meals an evening do that sort of thing.

That's interesting. I just had a wee look at the manual again. Looks like it would draw the max 32a with just two rings on boost, or one ring on boost and two others on the highest (non-boost setting).

A friend suggested I just plug the oven into the kitchen ring. But then I guess then I'm swapping the risk of overloading the oven cable with the risk of overloading the ring. And we already have a washer, dryer, fridge-freezer, microwave, toaster kettle and my home office equipment on that!

 

[pc1966]

Stick with the cooker circuit for now. If you run in to problems then you can see about alternatives, but I seriously doubt you will max out the circuit under any normal usage for a home.

 

[Markyd]

For domestic cookers the usual assumption is 10A plus 40% of the remaining load, plus 5A if a socket is fitted. So 32A becomes 10 + 0.4 * (32 - 10) = 19A.

Provided the supply MCB matches the cable rating it should be fine. Even hammering all outputs at once is unlikely to trip it in less than a couple of minutes, and usually the heaters are cycling by then to set temperature.

30%

 

[pc1966]

30%

Indeed, I checked and you are right.

For some reason i have 40% in my memory, maybe from some other project...