4mm cable, 32a breaker for 16.2kw Rangemaster installed by electrician

[timhoward]

Hello all.
I'm the first guy.
I couldn't fit the oven not because I refused to but because I was on holiday.
Are those saying you need 6mm on a clipped direct no derating factor 32a circuit saying they disagree with the iet table? I'm not trying to be argumentative, I'm just following the book. Surely the iet have checked these as a long term load.
Cheers
Gc

First of all welcome! I hope the above doesn't make too painful reading - there are certainly gentler ways to join a forum!

There were some early responses before the fact it was clipped direct came to light. After that I think there was a consensus that it was compliant and you'd done nothing wrong(!).
It's true that a few of us (myself included) did express some surprise mainly because it's not something we encounter too often.

 

[DPG]

Hello all.
I'm the first guy.
I couldn't fit the oven not because I refused to but because I was on holiday.
Are those saying you need 6mm on a clipped direct no derating factor 32a circuit saying they disagree with the iet table? I'm not trying to be argumentative, I'm just following the book. Surely the iet have checked these as a long term load.
Cheers
Gc

Welcome to the forum!

 

[mattg4321]

Can’t believe some here are advocating 10mm for domestic cookers. Absolutely no need unless it’s run through mountains of insulation making 6mm on a 32A OCPD non compliant.

Never known any domestic cooker to require more than 32A and I’ve had this argument many many many times before.

10mm for showers is another story. That I totally agree with.

 

[brianmoooore]

Shower is a known fixed load (often less than initially expected if the rating of the shower is declared at 240V), and is not normally used for more than about 5 minutes at a time by normal people.
A cooker is an extremely and constantly varying load, for which we use a diversity formula to give the long term average maximum load. At times, the load will be well over that diversified current, and well above the rating of a 32A OCPD for hopefully short periods. For these reasons I would not use a 4mm cable for a cooker such as this.
At today's prices, the difference between 4mm2 and 6mm2 is 58p/m, so on a 15m run, would only have made a difference of less than £9 to the cost of the job.

 

[nicebutdim]

Shower is a known fixed load (often less than initially expected if the rating of the shower is declared at 240V), and is not normally used for more than about 5 minutes at a time by normal people.

Perhaps you could educate people under the age of 30 on appropriate use of a shower. 20 minutes or more wouldn't be abnormal for many.

 

[mattg4321]

The shower is a fixed load until a plumber changes it for a 10kW one!

Most have cable runs through insulation as they are invariably run through lofts. This is not so for cookers.

I’ve clamped many a cooker and even with a large range cooker it’s surprisingly difficult to get over about 30 amps.

When you clamp showers then it’s almost always around 40 amps with modern units.

A shower is nearly always run at full load whilst a cooker is usually well below its maximum rated current.

Having said the above I would’ve run 6mm probably, although 4mm sounds ok in this case. 10mm is overkill for domestic cookers though. Just not needed.

 

[UNG]

Can’t believe some here are advocating 10mm for domestic cookers. Absolutely no need unless it’s run through mountains of insulation making 6mm on a 32A OCPD non compliant.

You give mountains of insulation as a reason but what about cables run in voids where the ambient temperature with heating pipes that can be at 60ºC+ is never really considered

Never known any domestic cooker to require more than 32A and I’ve had this argument many many many times before.

There are a lot of appliances where the ratings are grossly over what they will run at in normal use, I suppose some of the debate in this thread revolves around a cable that may be close to it's limit and how any future changes in the building fabric may push it over that edge a cable clipped direct could be a cable that is boxed in a few months down the line

While the regs appear to address most of the new technologies it would appear that cooking appliances have been overlooked can we really apply the same diversity to an induction hob as we do to a ceramic or halogen hob when they are using totally different technologies, the induction hobs I have clamped seem very power hungry when compared to the older technologies

10mm for showers is another story. That I totally agree with.

Since the first electric showers came to market at 6Kw the market has gone with bigger Kw's and even bigger Kw's is better and it is more likely you will find burnt cables and switches on shower circuits than cooker circuits

 

[spynage]

Hi, during kitchen refurbishment, the electrician installed a 4mm cable and 32a breaker for the new induction hob rangemaster oven that is rated at 16.2kw.

Same electrician couldn't connect hook up cooker, so I asked someone else to do it. The new electrician refused to connect up saying it needs a 10mm cable 45a breaker. Both professionals are in disagreement. Would be great to get a consensus here please. I want to use the oven without concern it may trip the breaker (5 induction hobs, 2 ovens and warming drawer)

Thanks

It will be fine. Should of used 6mm really as best practice, but it's not unsafe if it's fused correctly which it is. Due to the installation method the cable rating may be slightly below 32 amps but as others have said with diversity applied to the cooker your unlikely to use over 32amps anyway. I mean 32amps for cooking is so much! An oven on full power will draw 13amps max but then it will switch off intermittently once up to temperature. Induction hobs do the same with intermittent pulses. You shouldn't have a problem. If the breaker starts nuisance tripping though then you shouldn't ignore this, but I doubt it will happen.

 

[freddo]

Since the first electric showers came to market at 6Kw the market has gone with bigger Kw's and even bigger Kw's is better and it is more likely you will find burnt cables and switches on shower circuits than cooker circuits

Except on modern cookers that use very poor quality terminal blocks! There is such a problem of them melting and catching fire (often on the factory side connections) the manufacturers, instead of going back to proper heavy duty type found in most cookers when I was fitting and repairing them as a job 16+ years ago, are now supplying metal covers that go over the same crappy plastic terminal blocks to contain the fire. Product manufacturers and designers are morons.

 

[UNG]

Except on modern cookers that use very poor quality terminal blocks! There is such a problem of them melting and catching fire (often on the factory side connections) the manufacturers, instead of going back to proper heavy duty type found in most cookers when I was fitting and repairing them as a job 16+ years ago, are now supplying metal covers that go over the same crappy plastic terminal blocks to contain the fire. Product manufacturers and designers are morons.

And now back to the other thread about AFDD's