Hello all
My friend is renewing all his kitchen units and appliances, he has decided to fit ovens with ratings of 2.8kw (12A) and 3.6kw (15.7A), the hob will be gas, the cable to the cooker switch (with socket) looks like 4mm, from this cable (2.5mm T&E) went to a fused spur and separate cable (2.5mm T&E) to cooker junction box.
Will the 4mm cable be suitably rated for both ovens and socket on cooker switch?
If so will 2.5mm T&E be suitable for each individual oven and will each oven require a fused spur.
I will have to check the breaker to see if it is 32A, if so this will leave only 4A for socket, will this be sufficient.
I have a copy of the 17th edition and can look up tables etc if you let me know where to look for clarification.
All the best
Malky

4mm can take 37 amp

Thanks for your reply, I have checked the tables in the 17th edition and 37Amps is correct, will I need a fused spur for each circuit or can they be connected directly to the cooker switch.
Cheers
Malky

in my honest opinion that is a very bad way to do it anyway. i havn't seen any cooker circuit done in 4mm, it always used to be 6mm unless fitted in a council house and then it was 10mmm. we now always use 10mm.

using different sized cables in the circuit is bad practice. if you really do have 4mm cable then maybe it was a circuit installed for a double oven not a cooker?

if you are going to do this in the way you stated, the 2nd oven will blow the fuse in the 13A SFCU. this needs it's own circuit with it's own fuse rated at 20Amp with a 20A DP isolation switch. 2.5mm cable cannot take 37Amps and connecting 2.5mm to the 4mm to supply a 13A SFCU is wrong. you can have 2.5mm on the "load" side but not the "supply" side, that would need to be 4mm.

in either case, you need another circuit/point

I have only had a quick look at the wiring and have still to measured the cable conductors to get the correct size, I only think it is 4 mm, this cable is straight to the cooker switch from the mains box, I was hoping to take 2 off 2.5mm cables from the switched live / neutral of the cooker switch to 2 off fused spurs 16A and 20A, these would then supply the ovens, would this be okay?
Oven current rating are approx 12Amps and 16Amps.
Cheers
Malky

as i said, the fused spur will blow the fuse, this is the wrong way to do it.

I think I must be confusing you with my description of this circuit, the 4mm cable is from distribution board to the cooker control unit, from the switched side of the cooker control unit I would run one 2,5mm cable to a 13A switched fused connection unit and from here to the 2.8kw oven (circuit 1), I would then run a separate 2.5mm cable from the switched side of the cooker control unit to a 45 Amp Cooker Cable Connection Unit Single Plate and from here to the second 3.6kw oven (circuit 2), this would give a max current through circuit 1 of 12A, max current through circuit 2 of 16A and total max current of 28A + socket load of cooker control unit through 4mm cable.

This is how it is just now with an oven and a gas hob, I would basically be swapping the gas hob for another oven, 2.8kw.
Does this sound correct.
Cheers
Malky

We have to follow the regulations and it states 433.2.1 Except where Regulation 433.2.2 or 433.3 applies, a device for protection against overload shall be installed at the point where a reduction occurs in the value of the current-carrying capacity of the conductors of the installation.

So unless you install a mini consumer unit (As over 13A can't use fused connection units) you can't reduce the cable size.

4mm sq cable has not got "a" current rating but "a series" of current ratings according to cable type and installation method. This varies from around 17.5A to 45A. In a typical house we would expect to find "Reference Method 100" and thermoplastic cable so 27A. Hence why 6mm sq rated at 34A under same conditions is the norm.

As an electrician we would inspect and test before deciding on best method. Loop impedance being one of the tests. We would study the situation and recommend a method suited to that kitchen. In my mothers for example a mini-consumer unit was fitted. But this is a job for some one on site and to work this out on a forum is not really the way forward.

Since it is a special location and likely the LABC will need informing I would think the cheapest method would be to get a registered electrician to do the work. Rather than paying council their £100+ fee. So getting a quote will likely be best option as he will say how he would do it and likely his price will be same or lower than it will cost to DIY.

He has bought a mini consumer unit and 4mm cable, he is going to get an electrician in to connect up a whirlpool bath so he may as well get the electrician to do both jobs, this way it is all legal when he decides to move.
Many thanks to all who replied.
Malky