Diversity - 50A (max) of cooking appliance on 60A supply?

[KevDIY]

Hi,

I'm thinking of having a double oven and a 4-ring hob installed - rated at 4.4kw and 7.2kw respectively, so about 50A total/max. But the main supply to the house is only 60A and I'm unsure if theres enough diversity to make this a sensible idea.

Its a small house (one double plus two single bedrooms), and all heating and water is on gas so theres nothing else big on the electrics, but of course I do have appliances like toaster & kettle etc.

Is 50amps of cooking appliance on a 60A main supply reasonable, or would it be taking things too far?

Thanks
Kev

 

[Taylortwocities]

What else is electric in your house that uses a lot of energy.
Wash machine, tumble dryer? Got any instant heat power showers?

If you have gas, why not have a gas hob?

 

[JohnW2]

I'm thinking of having a double oven and a 4-ring hob installed - rated at 4.4kw and 7.2kw respectively, so about 50A total/max. But the main supply to the house is only 60A and I'm unsure if theres enough diversity to make this a sensible idea. ... Is 50amps of cooking appliance on a 60A main supply reasonable ...

'Reasonable' is difficult to define, but the official guidance on diversity says that domestic cooking appliance(s) with a theoretical total current draw ('adding everything up') of 50A only has to be considered as a representing a load/demand of only 22A (10A plus 30% of 40A). It would be 'normal' to supply such a cooker from a circuit protected by a 30A fuse or 32A breaker.

It's probably not that 'unreasonable'. Both of the ovens and all of the hobs will be cycling on and off due to their thermostats so that (except, very briefly, if everything were switched on simultaneously) the total current at any point in time is never going to be anything like 50A ... and, as for the occasional very brief 'exception which proves the rule', the supply (including the DNOs service fuse) would allow a lot more than 60A to flow for a brief period of time without any problem.

Kind Regards, John

 

[EFLImpudence]

It will be fine.

 

[JohnW2]

It will be fine.

Indeed - and a far more succinct answer than my one, which essentially said the same

Kind Regards, John

 

[EFLImpudence]

 

[KevDIY]

Great stuff - thats extremely helpful!

Thanks for the detail John, I wasn't sure what the official line was but I can see that short of whacking everything on to warm up at the same time (very unlikely with the hob in particular) the actual current drain will rarely and only ever briefly be the max.

Thanks also for chipping in EFLI - succinct it may be, but it all adds to the consensus

Cheers
Kev

 

[JohnW2]

Great stuff - thats extremely helpful! Thanks for the detail John, I wasn't sure what the official line was but I can see that short of whacking everything on to warm up at the same time (very unlikely with the hob in particular) the actual current drain will rarely and only ever briefly be the max.

You're welcome - and, yes, that is the concept underlying the diversity guidelines.

In fact, I think that there are some 'clever' hobs around which will not allow all four hob elements to be 'on' (i.e. drawing full current) simultaneously, even if all four are 'switched on', thereby limiting total current draw even if all four are switched on simultaneously from cold.

If you look at the instructions/spec of a 'double oven+4 hob' cooker along such as you described, you'll usually find that it will say that it (the whole thing) requires a '32A supply', even though 'adding up' would give a considerably higher total current than 32A.

Kind Regards, John

 

[KevDIY]

Thanks again, John.

The manual I have seen isn't especially helpful on the technical front, not mentioning fuse ratings for example. It did say that if the 'boost' is used on a special ring, it reduces power to the normal ones so as to maintain the total rating quoted. I'd guess if it did anything else clever it would probably say, or at least have a lower total rating.

Cheers
Kev