oven circuit cable size?

[mattc334]

Hi there.
Im new to calculating cable sizes and have got myself muddled up,please could someone help.
I am installing a radial for a new cooker 10.4kw and have an old wylex board with a spare 30a BS 3036 rewireable available.
I have worked out that with diversity that gives me 23a load,then factored in 30/0.725 for the fuse to give me 41.37a (In).
This will be run in mini trunking on its own over roughly 16 mtrs.
Looking in the reqs this is referene method B which would mean running the circuit in 10mm which seems excessive.
But as i said im new to this and am not sure if i am calculating right.
Any help would be really appreciated as i have spent far to long today driving myself mad with this
Thanks again in advance.

 

[nickblake]

I Think youve answered your own question here , cable size should be 10 mm , things i would like to point out that if the cooker switch has a socket outlet also you need to take that into consideration also would need RCD protecting and as is in a kitchen will be a notifiable works

 

[mattc334]

Thanks for that was not sure i got it right.
Was wondering if i changed the fuse rating or clipped direct if i coul get away downgrading to 6mm.
Thanks.

 

[Guest123]

At best, 6mm clipped direct will give you an Iz of 47A.

If it's a BS 3036 30A then then as you've said Iz must be greater than 41A, needs to be a 10mm IMO as installation factors will downgrade the 6mm to below the 41A needed.

A BS 3036 20A would need a cable with an Iz of minimum 27A so down grading to this would allow a 6mm to be used but you then may get issues with the circuit loading as even with diversity applied Ib comes in a 25.5A.

10mm is the only way to go IMO.

 

[mad frankie]

if you want to run a smaller cable you can use M.I.C.C expensive though look it up in the brb

 

[mattc334]

Hi.
one more thing,does a cooker cicuit have to have a RCD cant find that in the reqs.

 

[Mr Mark Sparks]

Hi.
one more thing,does a cooker cicuit have to have a RCD cant find that in the reqs.

not if there is no socket and you run surface

 

[mattc334]

Hi again.
Sorry to be a pain,but decided to install a new board as realised old wylex is only a 60a so would overload.
Im going for a new spilt board with mcb's so will be putting cooker circuit on a 32a mcb.
Looking in the reqs this seems to allow for 4mm as i have Ib 23A (with diversity) reference method b (in mini trunking)allows upto 32a.
Have i got this right or am i missing something.
Thanks again for any help.

 

[nickblake]

yes it does if i remember rightly its an A3 radial , but ill be honest with you i would install it with a minimum of 6 mm and the cost diffrance is neglible and your covered for full load , if you are changing the board ensure that this is a dual RCD board ,volex do one at screwfix for £59.99 fully loaded also dont forget this type of work requires a full test of the installation and notification to LAB

 

[mattc334]

Thanks for that.
I will do it in 6mm for peace of mind.
I have just got an account with electricfix so will get the board you recomend sounds like a good deal.
Thanks alot its good to re check my calculations.

 

[SirKit Breaker]

When I wire up cookers, i never bother with diversity. Just do the calc Kw / 230, and fit the appropriate size cable. However these things are getting a bit like showers now, so I generally bung a 10mm in anyway to the CCU, and whetever the spec calls for from CCU to cooker. It suits me, err's on the side of caution, and i hate maths as well.

 

[telectrix]

makes you wonder though, how much of a safety factor are the IEE allowing when they decree the CCC of a cable. years ago we tested some 2.5 on a variac load. pushed it to 72 amps for 30mins. got a bit warm, but no permanent damage to conductors or insulation

 

[Bigboy247]

You can always look in the cooker instructions, as they will set out the requirements and minimum fuse and cable sizes. As it states follow the manufactors guidelines.