Cooker Connection Unit wiring size

[riveralt]

I have a customer with a separate oven and hob total 6.4kw. The circuit is protected by a 32amp MCB with additonal protection provided by an RCD.
The circuit has 6mm cable from Consumer unit to Cooker switch and 6mm from cooker switch to cooker connection unit.
The hob comes with its own 4mm flex cable that will terminate at the cooker connection unit. The oven comes with its own 2.5mm cable and a fitted 13amp fused plug.

I plan to put a dual backplate and run cable from the cooker connection unit to a single unswitched socket. What is the minimum size cable I can use to connect the two together?

 

[Chri5]

Since the load is still restricted to 13 amp via the fuse in the plug 1.5 TE, but me being me I'd use 2.5mm

I take it you have designed the circuit so that hob + cooker with diversity cals means the existing cu arrangements are acceptable.

 

[riveralt]

Since the load is still restricted to 13 amp via the fuse in the plug 1.5 TE, but me being me I'd use 2.5mm.

I haven't fitted an oven with a plug yet and this is the first time I have utilised the dual backplate with the cooker connection unit (CCU) and single socket in one block. Most of the one's I fit tend to connect into a dual cooker connection unit with 4mm or 6mm cable to the oven or hob depending on the rating.

I was going to use 2.5mm but couldn't get out of my head the fact that this cable is rated at 27amps which is below the MCB. And the connection from the CCU although only short is before the protection afforded by the 13amp plug fuse. I might get away with fitting a 4mm between the CCU and the socket but the CCU will already have 12mm of cable its going to be a tight fit.

I take it you have designed the circuit so that hob + cooker with diversity cals means the existing cu arrangements are acceptable.

Yes I got just over 20amps after diversity.

Thanks for your help.

 

[holmslaw]

..

 

[riveralt]

Holmslaw, surely if I used 2.5mm from the CCU to the socket and that socket has a 13amp fused plug for protection then the max current applied through the fuse is 13amp (I know its higher before it blows) and therefore this protects the 2.5mm cable.

 

[holmslaw]

..

 

[riveralt]

Yes, but read 433.2 and 434.2.1, there are other specific conditions that must be met.

I'm unwilling to describe the ways to comply, because a diyer or dodgy spark could misinterpret my comments, look at 433.2 and 434.2.1.

Yes I have read this section and my only conclusion is that I must run 6mm cable from the CCU to the socket and only at this stage does the fuse in the plug protect the reduced size cable to the oven.

Putting an FCU (13amp) in the space next to the CCU and then run a 1.5mm cable to the socket is the only other option I can see which kind of defeats the object of have the dual backplate in the first place.

 

[riveralt]

Yes, but read 433.2 and 434.2.1, there are other specific conditions that must be met.

I'm unwilling to describe the ways to comply, because a diyer or dodgy spark could misinterpret my comments, look at 433.2 and 434.2.1.

The light comes on - I now understand - I also looked at page 363.


Many thanks.