Replacing electric cooker- 10mm cable for 10.7KW?

adrach · 19 Apr 2011

Hi. I've just bought a new cooker and I want to check whether the cable which is hard-wired to the old one will be adequate for it. The cable running to the old cooker is 10mm, and the new cooker (a Hotpoint HAE60P) is rated up to 10.7KW.

Comet have offered to install the new cooker for £70, but if it's simply a matter of removing the cable from the old one and attaching it to the new I'd rather save the money and do it myself, so I'd be grateful if anyone could tell me if there are other variables I'm missing here (I'm DIY-capable, but as you can tell I don't know a whole lot about electrics, short of replacing plugs, sockets etc!).

I would imagine there are issues I need to be aware of other than just the thickness of the cable, so I'd be grateful if you could tell me what these are (if there are lots, I'll probably just pay the installation fee).

Thanks in advance for any help with this.

Stoday · 19 Apr 2011

If you can connect a plug, you can connect your cooker. Nothing special.

You might find that there are three connections for the live terminal linked with copper strips. Don't let that faze you; connect to one of the three linked terminals.

You may find that your MCB in the consumer unit feeding your cooker is 32 or 45 amp. That's very unlikely to trip even though your cooker's maximum load is 64A.

1550 · 19 Apr 2011

Your local sparky will probably do it cheaper than that.
Some cookers are awkward to physically wire in, and can be a right pain. Some need the hobs linked- as some are designed for multi phases.

But 10mm is fine for that ,if that is what it is, and not a football field away from the CU.

I would ask a local sparky first to be truthful.

Edit : Stoday didn't mean to be contrary . I was typing as you posted lol.

Taylortwocities · 19 Apr 2011

Just two quick questions:
How did you measure that 10mm?
What fuse/contact breaker is in your fuseboard protecting the cooker circuit?

adrach · 19 Apr 2011

thanks for the replies.the fuse says 45A.I measured the width of the sheath and the flat bit is 10mm-with the curved edges it comes to12-13mm.is this ok?do you think I'll be ok to do this myself then?as I say,I can rewire a plug or socket but not done this before.cheers.

Taylortwocities · 19 Apr 2011

adrach said:
thanks for the replies.the fuse says 45A.I measured the width of the sheath and the flat bit is 10mm-with the curved edges it comes to12-13mm.is this ok?do you think I'll be ok to do this myself then?as I say,I can rewire a plug or socket but not done this before.cheers.

So that is NOT 10mm² cable. The 10mm refers to the cross sectional area of the copper conductor. Not the outside sheath.
There is a guide here //www.diynot.com/wiki/electrics:cable_types:flatpvccables

I would say that you may have 4mm cable, 6mm² at best. if so that 45amp fuse is probably too big.

1550 · 19 Apr 2011

No one can answer that but you I'm afraid. Your cable is more liklly to be six mm than 10mm . 6mm is good for 46 amps clipped direct and 38 amps in conduit or trunking. your cooker will have a diversity allowance , meaning that the total plate rating wont be required at the same time.
Hope this helps . Regards

adrach · 19 Apr 2011

thanks for the education!I think it's probably 4mm squared judging by those measurements.is this not likely to be enough then?

1550 · 19 Apr 2011

4mm is good for 37 amps clipped direct and 28 amps in conduit or trunking. Other factors affect the rating of the cable ,ie- run in insulation, this will reduce the current carrying capacity even further . Most cookers don't run at the plate rating -ie the grill and oven can't be used together. Check the data in your user instructions, or check with the manufacturer.

ajrobb · 19 Apr 2011

I am not an electrician. 45A is quite big for a cooker circuit and more common for electric showers. A 32A circuit is usually appropriate for household cookers up to 15kW plus a 13A socket. With a 32A circuit a 6mm² flex would be appropriate.

Household cooker circuits use a 'diversity' calculation that is the first 10A plus 30% of the remaining full-load current. The 13A socket is rated at 5A in the calculation. A 45A circuit could be used for 29kW of household cooking appliances!

Cables take quite a time to reach their steady-state temperature so can carry considerable extra current for a short time. An MCB has a thermal element that tries to mimic the heating of the cable and will allow extra current to flow for some time. It also has an electro-magnetic element that trips immediately for a current of 3-5 times the rated current (typical class B MCB).

ban-all-sheds · 19 Apr 2011

It really does sound like 4mm² rather than 6mm².

Should not be on a 45A MCB, let alone a 45A fuse, which if a rewirable type requires the cable to be rated at 62A, not the 37A (best case) that 4mm² is.

1550 · 19 Apr 2011

I suspect he may be looking at the Shower cpd , Local Sparky the best bet I think.

Stoday · 20 Apr 2011

The OP should not be calling in a spark to connect a cooker. It's reasonable to expect the circuit that was supplying the old cooker is also OK for any cooker up to 15kW.

Now, if there's a question concerning the adequacy of the circuit, a spark should be called in to give a report on the whole installation. If there's something wrong with the cooker circuit, so too may other circuits in the house have failings.

ajrobb · 20 Apr 2011

I agree, simply replacing a cooker on the old flex shouldn't be a cause for worry.

As a completely separate issue, if the OP has doubts about the house electrics then it may be time to get in an electrician for a Periodic Inspection Report (PIR).

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Replacing electric cooker- 10mm cable for 10.7KW?

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