UK Induction Hob Query

[Livingthedream]

Hi



I’ve just had a new kitchen and an induction hob installed which is on its own 32amp rcbo but my question is the total load rating is 7.35 for the induction hob which is just below 32amp if I’ve worked that out properly and it’s fitted to a cooker switch with a socket on which will have the microwave on as well so surely combined this would exceed 32amps, he used 6mm cable but should this be on a higher amp rcbo say a 40?



Also he’s put an outside socket in which is on a 16amp rcbo should this be a 32amp



I’ve not had any issues but I was reading the manual which got me thinking



Any advice appreciated

 

[pc1966]

I'm guessing that is 7.35kW rating?

At 230V that would be 32A, however, it is rare for everything to be on maximum for any length of time in a domestic cooker, so the IET guidance for diversity (i.e. the reasonable-case use of several loads, in this case differing elements, etc) for a domestic cooker is:

10A + 30% of the remaining current + 5A if kettle outlet fitted

So in your case that would be 10 + 0.3*(32-10) + 5 = 21.6A and so a 32A breaker is OK.

Probably the same with the outside socket. Without knowing the cable choice, length, and if it is a single or double socket, it is not possible to see if larger breaker would be acceptable or useful, but it is very unlikely you would have 2 * 13A load there so having a 16A breaker would usually be reasonable for that. Most likely it will be used occasionally for a lawn mower at ~4A or whatever!

 

[Livingthedream]

Many thanks for your prompt response

it is 7.35kw for the hob and to be honest I doubt it will ever have everything on

the outside socket is a double which is approximately 7 meters away from the consumer unit and is 2.5mm cable, it will be used 95% of the time for the lawnmower otherwise I might cut some wood with a mitre saw or similar

Thanks

 

[buzzlightyear]

the outside socket is a double which is approximately 7 meters away from the consumer unit and is 2.5mm cable, it will be used 95% of the time for the lawnmower otherwise I might cut some wood with a mitre saw or similar

that's fine on a radial 16 amp on 2.5mm
You can not put a 32 on a 2.5 or unless it is a 4mm.

 

[pc1966]

The other factor that impacts a cable's current carrying capacity is if it runs through thermal insulation, a hot area, or if it is grouped with other cables. Best-case rating (single run of 2.5mm clipped to a wall) you could get away with a 25A breaker, more general case you would stick to 20A or less.

Realistically you are unlikely to ever go above even 13A on that outdoor socket.

Only typical domestic case where a double socket runs higher than 16A is a typical kitchen with two heavy loads on it (like a washing machine and a tumble dryer) that are often used simultaneously. I think most electricians would opt for two single sockets in that case though as you find doubles tend to show signs of thermal stress after a while.

 

[Livingthedream]

Many thanks for your responses

this all makes more sense now

also the kitchen is on its own 32amp ring and he’s put singles on the washer, dryer and dishwasher like suggested so all seems well and it's reassuring that he’s done a good job

 

[pc1966]

Normally this sort of forum gets to hear of problems, such as the occasional cowboy/builder jobs or DIY disasters, so it is nice to hear a case of a professional job well done