Cable size for two ovens and a hob from extension CU with 6mm supply

[EFLImpudence]

I know but what about the other way round?

I am about to build an en-suite bedroom extension (with see above), can I power the bedroom consumer unit from the house cooker circuit in the next room?

The answer will obviously be the same but I will leave it to someone else to say "Yes, carry on".

 

[SJRSJR]

I'm confused about the origin of the supply cable.

Okay, so I should have been more precise. I say Consumer Unit as a collective term for the electric cupboard but what happens is that the electricity supply comes in and splits 1. to the Consumer Unit where RCBOs control the house excluding the extension, 2. to a Main Switch (on/off) from which runs the 6mm cable to the CU in the bedroom, which controls the extension circuits.

From what I’m reading (thanks for the comments), it may not be completely out of the question, but I should consider the combined power rating of appliances and how the cable is installed (Method C). Other than 400w of underfloor heating, the rest of the load is light.

I’ll think on and speak to the electrician, but just wanted to know what might/might not be possible. Thanks.

 

[JohnW2]

Whenever I've offered my doubts before there has been the chorus of a hob and an oven is no different to a cooker and the total power has diversity applied. On that basis 5KW = 22A + 13 = 35A, diversity comes out at ~18A not your 24.5A

Sure - but, since the OP was only talking about 'an option for' the hob (i.e. he might have only been interested in the ovens part), I was being 'conservative' by applying diversity separately to the oven(s) and the hob. ... but, yes, what you say further supports the 'bottom line' of what I wrote.

 

[JohnW2]

Okay, so I should have been more precise. I say Consumer Unit as a collective term for the electric cupboard but what happens is that the electricity supply comes in and splits 1. to the Consumer Unit where RCBOs control the house excluding the extension, 2. to a Main Switch (on/off) from which runs the 6mm cable to the CU in the bedroom, which controls the extension circuits.

Are you saying that that 'Main Switch' is 'just a switch' and is supplied directly from the output of the meter? If so, it should have a fuse or MCB (normally a 'switch fuse') protecting that cable to the bedroom CU.

 

[SJRSJR]

(normally a 'switch fuse') protecting that cable to the bedroom CU.

I hadn’t really thought about that but that makes sense. It’s definitely not an RCD/RCBO that trips and can be reset. I’ll need to check with the electrician. The CU is about 12 years old so I’m surprised it wasn’t done then.

 

[SJRSJR]

Came across this from 2014:
https://www.diynot.com/diy/threads/future-proof-oven-and-hob-circuits.417854/
Has anything changed re future proofing?

 

[EFLImpudence]

Okay, so I should have been more precise. I say Consumer Unit as a collective term for the electric cupboard but what happens is that the electricity supply comes in and splits 1. to the Consumer Unit where RCBOs control the house excluding the extension, 2. to a Main Switch (on/off) from which runs the 6mm cable to the CU in the bedroom, which controls the extension circuits.

Ok, so is it easy to run a 10mm² from bedroom to the switch?

 

[SJRSJR]

No, that’s the hardest part. If I had to do that I’d stick to gas even though I’d rather have electric.

 

[EFLImpudence]

No, that’s the hardest part. If I had to do that I’d stick to gas even though I’d rather have electric.

Ok.

Came across this from 2014:
https://www.diynot.com/diy/threads/future-proof-oven-and-hob-circuits.417854/
Has anything changed re future proofing?

No. It is a flawed concept.

Anyway, I, at least, am not even sure that what you want to do is present-proof.

 

[ericmark]

just as an aside, you may not like Electric hob , i know we didint like it when we moved in and had an electric hob, which i think had part induction - anyway we changed back to gas when i did my kitchen refit , ovens are great electric - just the hob we both didnt get on with
as i say just an aside

Oh, wonder why? I have found the hob left switched on that many times, I would not dare to use any hob which did not auto turn off. I found it a problem in the caravan, she would just fail to turn the hob off. However, we do have an induction hob with knobs on, I can't stand touch controls, but that's nothing to do with hob type, only time gas better than induction is when using a wok, as a wok for an induction hob is too heavy.

As to power, I have a 32 amp supply to my cooker, and if I exceed 32 amps for any length of time, the RCBO will trip. So if the cable can carry more than the Fuse/MCB/RCBO will allow, then it's safe. It may be inconvenient if the RCBO trips, but there is no danger. My cooker is rated at around 55 amps with everything on, but we will never have everything on, we had a Belling 4 ring and two oven cookers for around 25 years, and renewed it with one which looked nearly the same but with induction hobs, so it wastes less energy so does not matter what the rating is, it must use less. That one now 20 years old, both also had a 13 amp socket on the cooker supply, and neither have ever opened the Fuse/MCB/RCBO.

The question is if worth the risk it may trip? In the main my kitchen supplies have tripped due to earth leakage, not overload, and I have 3 power supplies to the kitchen, cooker, front of house, and fridge/freezer supply. The first 2 both 32 amp, the latter from a 5 kW inverter to two RCD 13 amp sockets, so power is retained even with a DNO power cut.

So as long as you don't change the trip size, there is no danger, that's what the trip is for. The old method to work out diversity does not work any longer, as the cooker does not heat the room any more, so clearly uses a lot less energy to the old ones, even if the rating is higher, the % time each ring is on is a lot less to the old cookers.