Help with cooker and hob cable

[martynluke]

We have just got rid of our old oven and hob which were connected together and came off one large (6mm) cable on a 45 amp isolator switch.

We now have a new oven (max output 3650W) and hob max output 4.8kw.
The electrician has advised to use the existing set up (6mm cable + 45amp isolator) for the hob.
And then a separate wire for the oven - 2.5mm - on a 20amp unfused double pole isolator.

Does this sound right? This seems small for the oven. Whilst he will connect we need to get the right cables in now.
He also says nowadays you don't tend to connect oven and hob.... hence doing it off 2 separate wires and switches.

Any help enormously appreciated. Thanks!!

 

[imroberts]

Is your electrician proposing running a new circuit from the consumer unit for the oven?

If so, then 2.5mm cable with a 20A breaker at the consumer unit would be adequate for the oven as 3680W is <16A.

Connecting the hob via the existing 6mm cable is also sensible as the hob is higher powered than the oven.

Given the ratings of the oven and the hob I'd have thought you'd be able to apply diversity and connect both directly to the 6mm cable. If the cable is connected to a 32A breaker at your consumer unit you shouldn't suffer from it tripping out under heavy load.

 

[LearningSpark]

What CPD's and cable sizes do the oven and hob manufacturers recommend in the instruction manuals? Why do you not believe what your electrician has recommended?

 

[riveralt]

We have just got rid of our old oven and hob which were connected together and came off one large (6mm) cable on a 45 amp isolator switch.

We now have a new oven (max output 3650W) and hob max output 4.8kw.
The electrician has advised to use the existing set up (6mm cable + 45amp isolator) for the hob.
And then a separate wire for the oven - 2.5mm - on a 20amp unfused double pole isolator.

Why didn't he fit it for you?

Does this sound right? This seems small for the oven. Whilst he will connect we need to get the right cables in now.
He also says nowadays you don't tend to connect oven and hob.... hence doing it off 2 separate wires and switches.

Any help enormously appreciated. Thanks!!

2.5mm cable has a current carrying capacity of 27Amps - you oven can draw 16Amps before diversity so the cable size is okay as is the 20 Amps DP isolator.

However, where do you intend to draw the power from?
If it from the 45Amp double pole isolator switch then what is the circuit protection for this circuit?
If the MCB is 32 Amps then you have a problem.

 

[martynluke]

I was originally hoping to come from the consumer board to a 45 amp isolator switch & then one 6mm cable going directly to the hob, and then from the hob straight to the cooker. Thereby eliminating the need for 2 isolators and adding a new cable to my only spare.

I only question my electricians comments as he did the initial work a year ago and can't get out to look at it for another month so it is all a bit by memory. I need the cables in before then.

I don't know anything about diversity - other than they have some great moves.....

 

[riveralt]

What do the oven manufacturers instructions say regarding the size of cable to use. Didn't the oven come with a cable?

What you propose is feasible but I'm not sure how practical is will be and again may breach the manufacturers instructions.

If the 6mm cable is protected by a 32Amp MCB then from the cooker switch run the 6mm to one of these:

http://www.alertelectrical.com/prod/1022/click-45a-easyfit-dual-appliance-outlet-plate

Then be guided by the manufacturers instructions regarding cable size - I would probably use 4mm as a minimum.