cooker cable size

[PrinceofDarkness]

I've known a few excellent college lecturers, they've been worth their weight in gold. But sadly they've been in the minority. I wish it were no the case.

Dodgy advice is dodgy advice wherever it comes, whether from the solitary word of a lecturer or a certain anonymous person on the internet....

Most people will take the advice from the person that seems to be on the same wavelength as they are.


Lucia.

 

[hoodie786]

use 10mm2 just to be on the safe side also prevents re wiring if you ever change the cooker or new occupier if the house is ever sod.



I AM JUST A HOODIE

 

[ColJack]

If this is a real-life. practical question, then 6mm will be fine on a 32A MCB for such a load even though it passes through a significant length of insulation (the which, could be avoided in most cases).

A domestic cooking appliance is hardly a continuous load 24/7 load, is it?

A domestic cooker stands idle for most of its life (it does in my house, anyway). But when it is called on, it seldom reaches its FLC for significant periods.

This is why we are allowed to use the diversity rules that have remained unchanged for more than half-a-century - with no apparent need for a change.

So, it's 10 Amps + 30% of the remainder etc......

10 to 12kW at 235V is roughly 47 Amps.

10A + 30% of 37A is roughly 21 Amps - which is half the rating of a sensibly installed 6mm cable.

So where's the actual drama?

Too many text books here........



Lucia.

not the point..
I don't deny diversity, but if your breaker is rated at 32A then the cable should be rated at at least that.. I don't give a rats ass what the load is.. could be 2A for all I know..

in the event of a fault that causes the cooker to operate at FLC for a period of time ( perhaps a pot boils over and shorts all of the controls out, leaving all of the rings on full and the ovens too.. who knows.. ), then the while the load will eventually trip the breaker, the under-rated cable in the mean time will melt...

while I've no doubt that this is a highly unlikely scenario the fact remains that to design a circuit where the cable has a lower current carrying capacity than the breaker is dangerous.. doesn't matter what the load is..

I can get a 9.5kW cooker on a 20A breaker with 2.5mm cable with diversity and it's safe, but I wouldn't put a 32A breaker on the same cable and call it safe..

 

[securespark]

I've known a few excellent college lecturers, they've been worth their weight in gold. But sadly they've been in the minority. I wish it were no the case.

Dodgy advice is dodgy advice wherever it comes, whether from the solitary word of a lecturer or a certain anonymous person on the internet....

Like you, you mean? You have offered Kevin dodgy advice.

Regardless of whether the kid is in school or college, whether this is theory or practice, your advice is not good.

If the regs say to derate because of factors such as trunking and insulation, then that should be accounted for. You take the worst-case factor and apply that.

And 433.1.1 still has to be adhered to.

Plus, you don't mention circuit length at all.

So, dear fellow, to say

6mm cable is more than adequate for a standard 32A cooker circuit, regardless of the method of installation.

is utterly reckless.

 

[ColJack]

that's what I tried to say earlier..

while we all know that on certain things the book is overcautious, the fact remains that you can't sign the test sheet saying that you designed it to the regs if you pick and choose which ones to follow..

 

[ban-all-sheds]

The use of diversity sets your Ib, it does not mean that you don't have to comply with Ib ≤ In ≤ Iz.

 

[PrinceofDarkness]

There's a hell of a lot of text-book-heroes on this forum.........

But not one of them can cite a single incident or accident concerning a standard 6mm/32A cooker circuit whatever the cable installation method....

Or can they?




Get your noses out of the book and get into the real world.


Lucia.

 

[GaryMo]

Lucia, the problem is that the installation will be designed and constructed to BS7671 and signed for as such.
It's not worth taking an engineered guess based on lack of previous incidents.

 

[PrinceofDarkness]

Thank you, Gary, but I don't agree with you.

There's plently of latitude allowed by the Regs, for those who are qualified to use commonsense.......

I say again: a cooking appliance is not a continuous load, therefore special rules apply.


Have you had a personal experience of a cooker cable bursting into flames, simply by being buried in insulation for part - or all of its length?

No? I thought not.....

Lucia.

 

[PrinceofDarkness]

Consider this: A sparky takes great pains to ensure that his cable is clipped to a joist above the insulation. Then, the householder receives a grant for a 'top-up' of insulation. The installer then covers the cable with insulation............

Is it the sparky's fault?

Do these 'Government approved insulation experts' have to follow BS7671? Willl their action result in a house fire?

I think not......


Lucia.

 

[GaryMo]

We cannot be held accountable for the actions of others in the future, only for ourselves up until we hand the work over as completed.