Upgrading Cooker MCB

Phantasm · 14 Mar 2004

Just had an electrician in to do some work on my kitchen before I get it plastered and all the new units put in. I\\\'ve bought a new electric oven and hob both of which have a max rating of 5.8kw. The electrician has moved my cooker point for me and I presume I can run both the oven and the hob off the cooker point but my distribution unit has a 40 amp limit on the cooker circuit.

If memory of my school physics lessons serves me correctly, 5800*2/240 = 48.3 amps which would pose a problem if i were to have the oven and hob all running at full power. Is it possible to upgrade my cooker MCB to a 50 amp one (assuming that the cable used for the cooker circuit is suitable). I know this is probably not strictly necessary as its unlikely that I would be using all 4 rings on the hob and both the top and main ovens at the same time.

The distribution unit i have is a Square D - Qwikline II if that makes any difference.

Big_Spark · 14 Mar 2004

Phantasm said:
The distribution unit i have is a Square D - Qwikline II if that makes any difference.

YUK!!!

However to actually be helpful, you oven and Hob are BOTH rated at 5.8kW? You sure?

The Hob I cab believe having a maximum rating of 5.8kW, however most ovens only have a rating of between 2.4 and 3.2 kW, the majority around the 2.8kW mark.

Also, your maths is wonky, you must work it out using 230V NOT 240V.

And lastly, if two items have 5.8kW loads, then each item should be on it's own circuit and protected by it's own MCB or preferably RCBO.

securespark · 15 Mar 2004

Could it be a double oven, FWL?

Big_Spark · 15 Mar 2004

securespark said:
Could it be a double oven, FWL?

It could be, but even then they are normally 2.2kW and 1.2kW.

Of course there are some very large double ovens on the market, but their ratings are dropping as technology improves..His next post will let us know no doubt.

Phantasm · 15 Mar 2004

Can I first ask why the YUK?

Secondly yes, its a double oven and from the online manual

Voltage: 230-240 Volts AC 50Hz
Wattage: 5.3-5.8kW
Height: 720 mm
Width: 593 mm
Depth: 585 mm
(excluding handles and knobs)
Weight: 60kg

Also from the zanussi website they state

Required Fuse (A): 30
Power supply voltage (V): 240

which would seem to tie in with the suggestion of 5.8kw.

So basically it sounds to me like i need to get my electrician back before the plasterer comes to get another cooker point installed.

hmmm... i was hoping that wasnt going to be the case.

Big_Spark · 15 Mar 2004

Phantasm, Yes you will need the Electrician back, tou cannot run two loads of that size from one supply, there is a real chance of overloading it and it simply is not worth the risk as it will be easy enough to do the work now.

The YUK is cos you said that name that no self respecting spark would install...Square D

What a cheap and nasty pile of poo...

Phantasm · 15 Mar 2004

Thanks for all your help and your quick responses. I better go and ring my electrician now.

Phantasm · 15 Mar 2004

Just spoken to my electrician and he suggested that he thought it would be ok running both off the one cooker point except for at christmas time when i might need both ovens and all 4 hobs.

He said he would be happy to run another cooker unit from the consumer unit for me if I wanted one, and I asked him to do so.

Does that suggest to anyone that he might not be a very good electrician?

PS it wasnt him who fitted the Square-D consumer unit, that was a different electrician when I had my house re-wired a year or two ago. Seems like I am plagued with shoddy workmen. Also can i ask is there anything in particular that makes Square D cheap and nasty - is there any good reason for getting it changed as well?

Millennium_Boy · 15 Mar 2004

I thought Volex was the hated brand...

Anyway all din rail consumer units are well pretty much the same nowadays-as I hear. Just that Wylex has a good feel to the name.

Big_Spark · 15 Mar 2004

Millennium_Boy said:
Volex .

How dare you use such vial language on a public form, go wash your mouth out with carbolic acid!

Big_Spark · 15 Mar 2004

Phantasm said:
Just spoken to my electrician and he suggested that he thought it would be ok running both off the one cooker point except for at christmas time when i might need both ovens and all 4 hobs.

He said he would be happy to run another cooker unit from the consumer unit for me if I wanted one, and I asked him to do so.

Then he is a fool if he thinks that running two fixed appliances off one circuit designed for a single appliance is acceptable, although I am glad to see he seemed to think about it and backtrack by bringing up Xmas.

He would be glad even if it was unecessary as you are putting money in his pocket..sorry I am that cynical

securespark · 15 Mar 2004

FWL

You, like I, take great delight in the use of the word "poo". You can add a lot of venom to it, and it's not too rude!

Although my 4 y.o. would disagree. He takes great delight (as kids of that age do) in saying all the rude words he can think of in rapid succession, then laughing like a drain!

His favourite is (this might be edited)

"poopoobumbumfartyknickersboobynippy......etc" You've got the idea!!

wilts sparky · 25 Oct 2004

FWL_Engineer said:
Phantasm said:

Just spoken to my electrician and he suggested that he thought it would be ok running both off the one cooker point except for at christmas time when i might need both ovens and all 4 hobs.

He said he would be happy to run another cooker unit from the consumer unit for me if I wanted one, and I asked him to do so.

Click to expand...

Then he is a fool if he thinks that running two fixed appliances off one circuit designed for a single appliance is acceptable, although I am glad to see he seemed to think about it and backtrack by bringing up Xmas.

He would be glad even if it was unecessary as you are putting money in his pocket..sorry I am that cynical

He should also have thought that a standard cooker cable of 6mm² is only designed to carry a maximum of 46A if installed correctly. Your 50A mcb would last longer than the cable in a fault condition.

Maybe you should consult another electrician, or ask to see the cable calculations.

securespark · 25 Oct 2004

Wilts

Why the interest in a thread from 7 months ago?

Damocles · 25 Oct 2004

The householder was asking about increasing the mcb to 50A, not his sparks. His sparks was, quite correctly, suggesting that 40A wouls be a sufficient supply for both cookers.

It is quite normal to assume that not all elements of a cooker will be operating at full power at once. In fact this is very unlikely, if you consider that they work by switching the heating elements on and off every now and then.

Cooker diversity rules are 10A plus 1/3 of remaining theoretical load. Taking the two devices separately this gives 10+10+ 1/3(30)=30A

So a 30A would likely do, never mind 40. Calculations like this are a bit rule of thumb. It is not obvious why separate hob and oven units should be treated any different from an all in one cooker. In that case it would be 10+ 1/3(40)=23A.

I am assuming this is a house, not a restaurant.

MCB are designed to tolerate temporary small overloads, though I doubt it ever would be.

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Upgrading Cooker MCB

Big_Spark

Big_Spark

Big_Spark

Millennium_Boy

Big_Spark

Big_Spark

Similar threads