Intepreting an electric cooker manual

[adrian1810]

I have purchased a double oven electric cooker. I wanted to know the cable size to use when wiring it up. The first page of the manual states

"The electrical connections must be connected to the terminal block as detailed opposite. A cable of the correct rating of this appliance must be used type H05 RR-F section 6mm2. "

Then on the opposite page it refers to it in the above statement, it says

"Connecting Mains Cable: Remove plate behind cooker. Insert the mains able (type HO5 RR-F) of minimum 10mm2 section into the cable protector. Connect wires to live, neutral etc...."

I'm confused over whether I should use 6mm2 or 10mm2 cable. Any suggestions? You probably can work it out from the Max Rated Power of the cooker which is 10.96Kw.

Ade B

 

[BR]

More info please, are you putting the cooker in from scratch i.e. new cable from CU to switch to oven or just replacing an existing cooker?

Your cable size will definitely be 10mm2, 10.96KW is over 45A and therefore you will need a 50A breaker.

You have 2 possible problems; If you have a 60A supply this cooker will overload it. Especially if you also have an electric shower.

If you are replacing an existing cooker the wiring from the CU is probably only 6mm 2, which is rated for 40A max. You would also have to look at control switch.

Bear in mind that this is the max load, i.e with every single thing going full blast. However installations should be designed for worst possible scenarios.

 

[adrian1810]

The good news is I am getting a spark in to replace my existing consumer unit to a modern unit and replace the existing cooker (including the rewiring) with this new cooker. I assume from your previous comments that I will need a cooker switch with a 50amp rating ? I had a quick look on tlc-direct but they're all 45amp - any suggestions where I could pick one up.

Thanks

Ade B

 

[ban-all-sheds]

TLC do this (63A):

But it's not very domesticated

But your sparky will be able to source one - they do exist - I know that Crabtree make one, for example.

 

[dingbat]

I have purchased a double oven electric cooker. I wanted to know the cable size to use when wiring it up... I'm confused over whether I should use 6mm2 or 10mm2 cable. You probably can work it out from the Max Rated Power of the cooker which is 10.96Kw.

You use the diversity rules to work out 'assumed demand' (Table 1A IEE On Site Guide, p.85) which, for a cooker goes like this:

First 10A of rated current, plus 30% of remainder, plus 5A if a socket outlet is incorporated into the cooker isolator. So: A 10.96kW cooker will draw 48A (assuming 230V, which you should). So you need a cable that will carry 10A plus 30% of 38A = 22A (rounding up) plus another 5A if you have a socket.

a 6 sq mm T & E cable with a 32A protective fuse/mcb is what you need (unless the cable run is greater than about 40m

 

[ban-all-sheds]

That's all true, and all very well, as long as Adrian is aware that he cannot start up the entire cooker at once - if he fires up both ovens and all the hotplates from cold, then it will draw 48A until it reaches operating temperature or the MCB trips, whichever comes first. How long will a 32A Type B pass a 50% overcurrent?

 

[BR]

Are cooker control units incorporating a 13A socket still allowed in the UK? They are not in Ireland due to the fact that a 13A socket must be protected by the RCD and since it is not appropriate to protect the cooker circuit with the RCD......................

 

[BR]

One could say what is the point in having two ovens if you cant use them both together??

 

[tucker]

I believe my situation is similar to adrian1810's...

I've just been given a cooker (Creda Concept) thats rated at a max of 10.96 - however, the max load on my cooker circuit is 30amp.

The cable on both my cooker mains AND cooker itself is 6mm2 - apparently the cooker (with 6mm2 cable) was used like this for a couple of years with NO problems - plus, I saw the cooker in operation shortly before it was disconnected, so I know it works!

I've yet to speak to the the cookers' original owner to ask them about the rating of THEIR cooker circuit...

Going off what I've read here, I should be able to operate my cooker at certain tolerances, yes?

It's a double oven - but I'd NEVER use both at the same time, plus I'd never need to have all hotplates on at the same time either (single bloke, I think you get the picture!) most likely a combo of 2 hotplates + oven would be all I'd be using.

I appreciate that getting EVERYTHING brought up to spec is the best way to go, but I lost my job a while back and therefore I simply can't afford a rewiring job on the cooker circuit.

Also, my control unit is rated at 45amp.

Bottom line is this: can I use my cooker safely with the facts I've given?

Any clarification would be appreciated!

Tucker.

 

[Steve]

worst that could happen - MCB trips. You aren't going to set fire to anything, dont worry.

 

[plugwash]

Are cooker control units incorporating a 13A socket still allowed in the UK? They are not in Ireland due to the fact that a 13A socket must be protected by the RCD and since it is not appropriate to protect the cooker circuit with the RCD......................

hmm are you just repeating heresay or do you actually know irish regs that back that up (if the uk is anything to go by there is a LOT of misinformation spread among sparkies and diyers alike)?

in BS7671 (which is the accepted standard but not in itself law) only sockets that can "feasiblly supply equipment outside the equipotential zone" have to be on a 30ma rcd. This is one of the most vauge and disputed regs arround as there is no exact definition of feasiblly. The NICEIC say all downstairs sockets but thier views are far from representitive of all sparkies.

also there is nothing in the regs that says cookers can't be on RCD its just some older ones are known to cause tripping problems (i personally think the single RCD CU is one of the worst things that ever happened to british domestic wiring practice but thats another issue).