Required Wiring for an Electric Cooker and Induction Hob?

[dwarfer16]

Hi Everyone

I am looking to re-model my kitchen including an Induction Hob and Electric Oven (currently we have gas). Now I am hoping that behind my cooker I will find an old electrical feed to the fuse box which was [once upon a time] used for an electric cooker. I think this because in my fuse box there are five fuses and one empty slot, on the removable cover it has 'cooker' written where the empty slot is. If I manage to find this cable I need to know if this one cable and fuse can handle both device. The power requirements for them are:

Oven: 7.2kw
Hob: 5.5kw

By my calculations this adds up to 55.2A ((7200w+5500w)/230V). Then I found information today that this isn't necessarily the requirement, according to the 16th Edition(for cookers) you only need to account for the first 10A of this load plus 30% plus 5A for the socket. This works out to:

(55.2-10)*0.3+10+5 = 28.5A

I got this information from http://www.tlc-direct.co.uk/Book/6.5.2.htm (I realise this is 16th and there is a 17th now which I need to check so I am assuming this part hasn't changed).

Does this mean that one cable will be sufficient to connect both the hob and the oven to the fuse box with a 32A fuse or have I misunderstood?

I would appreciate any help anyone can provide as I have read quite a bit of conflicting information/advice.

Thanks in advance, Craig.

 

[PrenticeBoyofDerry]

Providing the circuit is still a safe condition for continued service, then your calculation are correct. Diversity will allow for these two cooking appliances to be powered from the one circuit. Generally YOU will find a 6.00mm T&E cable supplying the cooker.

 

[dwarfer16]

Thanks for your very prompt reply PrenticeBoyofDerry.

I must admit, I do not fully understand why there is this calculation. Surely if the hob and oven was on at full power, it would be drawing approx 55A so shouldn't the cable and fuse be able to accommodate this or is it assumed that the maximum load will never be drawn for a hob and cooker because you wouldn't ever have everything on?

Cheers.

 

[winston1]

Basically yes. You are never going to have both the oven and hob on together at full load.
Personally I would, in fact I did, use 6mm cable and a 40amp MCB.

Puzzled why 5amp is considered enough for the socket when most people use it for a kettle.

 

[EFLImpudence]

Basically yes. You are never going to have both the oven and hob on together at full load.
Personally I would, in fact I did, use 6mm cable and a 40amp MCB.

You can now but the 6mm² cable would be too small for a BS3036 40A fuse.

You could now replace the cable with 4mm but hardly worth it.

Puzzled why 5amp is considered enough for the socket when most people use it for a kettle.

It just goes to show how well diversity works.

 

[dwarfer16]

That's great news. So either way, one cable will suffice with either a 32A or 40A fuse.

Can I also ask about the cable, again, I have read lots of information but the general consensus seems to be that 6mm cable is needed. Is this correct?

If I am able to find the original supply which would have gone to the old electric cooker and it isn't 6mm, I presume it should be replaced? The house was built in 1979 and all the wiring seems to date back to that time so I don't know if it would have been 6mm then or not.

Again, any advice is appreciated, thanks.

 

[EFLImpudence]

That's great news. So either way, one cable will suffice with either a 32A or 40A fuse.

MCBs. You cannot use a 40A rewireable fuse.

Can I also ask about the cable, again, I have read lots of information but the general consensus seems to be that 6mm cable is needed. Is this correct?

If you find one it will more likely than not be 6mm².

If I am able to find the original supply which would have gone to the old electric cooker and it isn't 6mm, I presume it should be replaced? The house was built in 1979 and all the wiring seems to date back to that time so I don't know if it would have been 6mm then or not.

4mm² will still be sufficient for a 32A MCB which will be acceptable for what you require..

 

[dwarfer16]

MCBs. You cannot use a 40A rewireable fuse.

.

Thanks EFLImpudence. I am actually having the fuse box changed over for a modern consumer unit (by a sparky), I am just trying to keep costs down by doing as much prep/research as possible.

 

[OwainDIYer]

Puzzled why 5amp is considered enough for the socket when most people use it for a kettle.

Because a kettle is usually used only for a few minutes at a time.

 

[Risteard]

Surely if the hob and oven was on at full power, it would be drawing approx 55A so shouldn't the cable and fuse be able to accommodate this or is it assumed that the maximum load will never be drawn for a hob and cooker because you wouldn't ever have everything on?

Even if you did have everything on together you would not draw this load as the elements cycle on and off and therefore aren't all running at full power all the time. As for the induction hob you have probably been quoted total connected load which is not necessarily the same as it can draw, as they have power sharing built in whereby, for example, if you boost one induction zone it may reduce power from another and so cannot draw the full load.

 

[ban-all-sheds]

Because a kettle is usually used only for a few minutes at a time.

Unless you buy one from Clas Ohlson, which (if left unattended) will run for quite some time, until all the water has evaporated, and then (presumably - I declined to find out) start to get very hot indeed.

 

[OwainDIYer]

Because a kettle is usually used only for a few minutes at a time.

Unless you buy one from Clas Ohlson, which (if left unattended) will run for quite some time, until all the water has evaporated, and then (presumably - I declined to find out) start to get very hot indeed.

Just because it's sold by Clas Ohlson doesn't mean it's made by Volvo

 

[ban-all-sheds]

Hokikoki Enterprises, Guangdong province, probably.