Cooker circuit query.


My cooker circuit is currently fused at 30A and supplied by a (rather ancient) 4mm cable. As part of the rewiring the circuit will now be fed from a 32A MCB and my electrician has suggested using two new 2.5mm cables to supply it instead.
While it seems to make sense to me, I'm a little worried that he's only suggesting it so that he can use up the 2.5mm he's got left...
I'm probably being a bit too paranoid and I'd be very grateful if someone could please confirm whether it is acceptable to use two 2.5mm cables in this fashion.
Many thanks,
Ben
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Benjamin wrote:

2.5mm is good for 27amps IIRC. What's the wattage on your cooker?
Both my hob and oven are on separate 4mm cables.
Mike
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Are you sure that he is a qualified electrician and Part P registered. ?
Sounds like a ruddy cowboy to me
--
the_constructor



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the_constructor wrote:

That would be my take on it too. I don't know much about the latest wiring regs but I would have thought that paralleling cables is not considered best practice. What happens if one cable works loose or is accidentally cut frinstance?
--
Malc

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My instinct is that you should insist on a single cable, 4mm.
IIRC, the load the cable can safely take is proportional to the cross-sectional area. So 2 x 2.5mm sqrd gives you 12.5 mm^2 but 4mm sqrd gives you 16mm^2. The actual copper core diameter is much less than 2.5 or 4.0, but I guess the principle holds good.
Also, shouldn't the fuse (or trip) be rated to protect the cable? - so the cable has got to be safe at 32 Amps.
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Martin

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It isn't quite like that. The quoted size of conductors refers to sq mm in area, therefore 2.5sqmm x 2 = 5 sqmm, whereas 4 is just 4. Having said that, I would use 6.0 to give bags of safety factor. You may have a bigger cooker in the future.
Steve
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Ah - that makes sense. Thanks for putting me right....
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Martin

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Using 6mm or indeed 10mm on some cookers is the norm.
You forgot about the earth loop. Two 2.5 T&Es have a combined cpc of 3mm, whereas 4mm I think (never bought any) has only 1.5mm cpc. It would be possible to use longer runs using two 2.5mm cables.
Regardless, insist upon 6mm as the minimum size.
Adam
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Cooker circuits are normally wired in 6mm t&e not 4mm and fused at 32a. Ring main circuits are normally wired in 2.5mm t&e fused at 32a. At the breaker of a ring both cables (2.5mm) are connected together as they are at each socket outlet hence the term ring.(very few work loose)
Whilst very uncommon running a 32a cooker circuit as a dedecated ring is not (as far as I am aware) against any regs'
However unless your cooker is miles from the mains the cost of a length of 6mm is nothing compaired to the hastle of running 2x2.5mm cables as a ring. And most sparks carry 6mm as stock.
HTH CJ
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