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Maximum load cooker requirements

Hi

I have recently started to renovate the kitchen and have a new range cooker. The cable that supplied the old cooker is a 2.5mm^2 which I assume to be 30A. I know that cookers should have a 6mm^2 cable. However after speaking to hotpoint they said maximum load would be 22.3A, from this it seems that the current cable would be capable of the full load.

Can someone give advice on if the current cable is OK? As replacing the cable would be a pain in the **** as the walls have just been replastered.

The cooker is a hotpoint EG902GX

Thanks

Reece

Thanks for all of the responses. I am going to get the cable replaced with some 6mm or 10mm. My logic is 6mm will be ok for now but should the wife want to have an all electric range in the future then 10mm would seem sensible.

Also the circuit is protected by MCB and RCD from a Dual RCD CU. There are also two other on the RCD, the kitchen ring and downstairs lights.

A quick question about the Diversity Factor. I can understand how this would work if the cooker was full electric ie 2 ovens, warming drawer, 4 rings + socket. Then I can see how you would not assume full load.

How does this work when there is only a double oven, as I would assume that there will be times, such as when you turn both on to heat up they will be drawing maximum current? Is this correct or am I missing a trick.

8 Answers from MyBuilder Electricians

Best Answer

I hope you are still there on this one a 6mm cable should be correct for this one
and almost definitely correct for a future cooker as well there is a formula to assess the current required for an electric cooker that allows for Diversity
The first 10 A of the rated current plus 30 % of the remainder of the rated current in excess of 10 A plus 5 A if a socket-outlet is incorporated in the cooker control unit
example 40amp cooker rating
take first 10 amps leaves
30amps x 30% leaves roughly 10 amps
so first 10 + the 30% 10 makes 20 Amps plus if you have a 13Amp socket on the cooker control panel/switch add 5 Amps
makes a total of 25Amps = 6mm cable on a 32Amp MCB (Breaker)
I hope this is not to complicated but it will save you installing a 10mm cable thus leaving a little copper for the rest of us ( Very Green ) saves on your pocket to
if you like this then hit the like button
Kelvin
A cooker with 2 ovens only and no separate rings etc I would check with the manufacturer if the diversity factor could be applied or not. They should know and advise.
In addition, the cooker you are about to install does require a 6mm cable if you are intending to install a range cooker later that is all electric then the diversity factor could be applied.
some cookers with double ovens only allow the use of one at a time so check first. Also in the others the diversity factor is worked out that even if you had most of the cooker working at one time the thermostats controlling separate rings and each oven would operate when that section reached the desired temperature then turn off until it cooled down enough to turn back on, as this would occur at different times across the cooker the full load would not normally occur or if it did it would be for a very limited time and should not therefore present a problem.
I hope this explains the theory ok.
If it does then hit the like button
Kelvin

2011-10-13T17:50:04+01:00

Answered 13th Oct 2011

You should not be touching the kitchen electrics yourself,it is illegal.All kitchen & bathroom electrics should only be installed by a part p or similar compliant electrician.Do yourself a favour and hire a professional to do the job correctly.

2011-10-09T23:35:04+01:00

Answered 9th Oct 2011

Hello,

If its Flat Twin & Earth BS6004 cable enclosed in trunking or conduit its rated on 23A, if its directly clipped its rated 27A.

If its enclosed in an insulated wall it will be 18.5A

My advice is to replace it with 10mm2 T+E cable

Regards
Martin

2011-10-09T23:35:04+01:00

Answered 9th Oct 2011

the current carrying capacity of a 2.5mm radial circuit routed as per reference method A (enclosed in conduit in thermally insulating wall, ect.)is 20 amps.

Clipped direct method c would be 27 amp.

So if sticking to method A you would need to run 4mm T+E which allows 26 amps.

The reason diferent meathods have different current capacitys is to do with the ability to disipate heat.

These figures are directly taken from the 17th edition on site guide.

Also changing the oven is not notifiable works if you do not have to alter the supply.

hope this info helps-Kevin.

2011-10-10T09:35:02+01:00

Answered 10th Oct 2011

i would strongly suggest using 6mm cable with a 32amp mcb

A sinlge run of 2,5mm should not be run through an MCB greater than 16amps

For 32 amps on 2.5 cable a ring main should be run

2011-10-13T17:50:05+01:00

Answered 13th Oct 2011

the maximum current rating of a 2.5mm cable varies dependant on length of run ( volt drop ) and installation method ( buried in plaster , clipped direct , concealed in trunking , etc . Assuming that the voltage drop is not an issue as the cable run is not that far between consumer unit and cooker outlet and the cable is buried in a plastered wall then the maximum current rating of such cable would be 18.5 amps . IF max load is 22.3amps and max cable current rating is 18.5 amps then it would require you to replace the existing cable to at least 4mm ( 25 amps ) . 6mm would be better to cover future increase in oven size and potential useage of cooker switch with socket outlet .

2011-10-10T09:35:01+01:00

Answered 10th Oct 2011

the cable should be replaced for a 6mm t/e on a 32amp mcb and the board must have RCD fitted
connect the cooker and the new cable with corect conecting plate
with isolation switch above work surfaces

2011-10-09T23:35:04+01:00

Answered 9th Oct 2011

Hi, it really all depends on how the cable is run. If it is conduit inside an insulated wall, the current carrying capacity could be reduced to as little as 18A! If it is under the floor/ceiling,not covered by insulation and clipped directly to the joists, then you should be ok (possibly up to 27A), but i would recommend upgrading if at all possible.
Hope this helps a bit.
Mark
Sparkright electrical services

2011-10-09T23:35:04+01:00

Answered 9th Oct 2011

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