Which cable size ?

[addgason]

Hello All, I have a 4.0 KW double built in oven to connect up the to the consumer unit.
This will be a radial circuit, in a 3 bedroom semi-detached house.

The length is about 20 meters mostly in its own hole in the joists under floor boards and 6 meters in its own trunking 38mm X 25 mm.

Can I just check is 4.0 mm2 twin and earth cable size ok with a 20 amp MCB in the consumer unit.
With a 20 amp double switch with neon light which will be behind the double built in oven, plenty of depth space.
FYI You can’t get double built in oven’s in gas anymore.

 

[EFLImpudence]

Do you not already have a 'cooker' circuit?

 

[addgason]

No pal, just a spare MCB in the consumer unit.

 

[addgason]

I’m going to use 4 mm2 Twin & earth cable with a 50mm pattress box including cable clamp & earth connection, with a 45 amp cooker switch which will be installed in the pantry next to the double oven unit, with another 50mm back box & cooker outlet connection being installed behind the double oven fixed to the wall, all cable will be inside 38mm X 25mm trunking.

OR

I can just wire the 4 mm2 straight into a cooker outlet connector behind the double oven, not have the 45 amp cooker switch in the pantry, just have the 20 amp MCB in the consumer unit, for isolation.

What would you guys recommend as the best practice installation please.

 

[SUNRAY]

Well for a start this site: https://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

comes up with ths calculation for 4.5KW and 30m:

Personaly I'd stick with the 4mm² as it'll cost a lot more to upgrade in the future when a larger cooking device is wanted.

Personally I would have a local isolator

Having read this thread again, Taylors advice in the next message is the correct route.

 

[Taylortwocities]

No pal, just a spare MCB in the consumer unit.

Sorry to be a pedant…
Just to point out that this is a new circuit and therefore it is notifiable work. IMO if you need to ask very basic questions about cable sizes you won’t be able to persuade LABC that you have the knowledge to do this.
You need a competent electrician who is registered with one of the CPS (NICEIC, NAPIT, etc) that person can then do the necessary test, certification and notify LABC.