fitting new ceramic hob and double oven

[sweets474]

Hi there,

We have an existing double oven with a 20A supply from the consumer unit.

We're planning on replacing our gas hob with a ceramic hob.

Most ceramin hobs are stating that it needs 32A supply - do i need to have individual supplies for the oven and hob?

Would it also be a good idea to upgrade the 20A MCB + cable?

Thanks

 

[PrenticeBoyofDerry]

They don't need separate circuits, but you will need to know the total output of the appliances, so breaker size and cable size can be worked out.

 

[ban-all-sheds]

• http://www.tlc-direct.co.uk/Book/6.2.1.htm
  
  
• //www.diynot.com/wiki/electrics:mcbtocable
  
  
• http://www.tlc-direct.co.uk/Book/4.3.1.htm
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/cableselection_web.pdf
  
  
• http://www.tlc-direct.co.uk/Book/5.3.1.htm
  
  
• http://www.tlc-direct.co.uk/Book/4.3.11.htm
  
  
• http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html
  
  
• http://www.tlc-direct.co.uk/Book/8.1.1.htm
  
  
• //www.diynot.com/wiki/electrics:part-p
  

 

[Taylortwocities]

We're planning on replacing our gas hob with a ceramic hob.

Why on earth would you want to do that, a gas hob is a far better cooking device than a ceramic hob.

Most ceramin hobs are stating that it needs 32A supply

Don't make that assumption, some need more. What are the power requirements of the one that you plan to install. That is key info and can't advise without that.
Need info about that oven too!

 

[sweets474]

My cable size is 6mm, the new hob is 7400w which i've worked out to be 30A, the oven we're planning on getting says 25w power? this doesn't seem right but it states it needs a 30A fuse.

I don't think my 6mm cable will be able to supply both - what do you think. The isolation socket is about 5m from the consumer unit.

What would be a recommended way to progress - replace the cable to supply both electrical devices?

Thanks

 

[ColJack]

25W? that's surely just the info for the replacement bulb in the oven? unless it's an "e-z-bake" oven?

 

[sweets474]

i think your right - it's probably the bulb replacement rating.

The only info i cant get from the manufacturer is that a 30amp fuse is required! There are no actual power values.

 

[PrenticeBoyofDerry]

Do you have the correct spec for the oven 25w can't be right.
Your current oven will require about 32A on maximum demand but will be fine on 30A.
6mm cable depending of method of installation can carry up to 47A

 

[PrenticeBoyofDerry]

The only info i cant get from the manufacturer is that a 30amp fuse is required!

If the manufacturer instruction state 30A is required that is usually okay.
But there should be an output rating given on the document or on the cooker plate.

 

[sweets474]

alas - i've found the rating! on another web site...

the oven rating is 5.3kW + the new hon is 7.4kW.

I make this to be a 52amp demand. I're read about diversity - would there be any way my 6mm cable could supply these devices?

Thanks for immediate responses

 

[echoes]

http://www.tlc-direct.co.uk/Book/6.5.2.htm

At 240V, 12.7kW is 53A. With diversity the demand could be estimated to be 23A. Or 38 A if we consider the hob and oven separately.

So depending on cable de-rating factors, 6mm2 protected by 32A MCB would be the absolute minimum. 45A using 6mm2 OK if cable derating/voltage drop permits. BAS has helpfully (as usual) posted all the useful links.
10mm2 protected by 45A MCB may be the better option. And I would not recommend a CCU with a socket for this load. Plenty of folk would never recommend them.

Or run separate circuits to the oven and hob, but this is OTT.

 

[Taylortwocities]

Or run separate circuits to the oven and hob, but this is OTT.

It is not OTT, it is the proper way to do the job.
Using diversity on these loads is a fudge IMO.

 

[sweets474]

thakyou all for your assistance, you've given me plenty to think about

 

[echoes]

Just re-read, and since you already have a 20A circuit for your oven (that's on the ragged edge for 5.3kW), it may be simpler to run a separate 32A circuit for your hob, provided you have a spare way on your CU. Then you can avoid resorting to diversity factors to calculate the load and have a robust arrangement.

Agree that using diversity for cooker circuits is less than ideal at best, and an arbitrary fudge at worst, but the OP did ask and the answer is yes, but there are significantly better options.