16.5kw Electric Cooker, What size Breaker? Pictures added

[cam1989]

Why are people seemingly questioning the competence of the electrician?

I work in building services design and we would never apply diversity to a final circuit, unless we had it in writing from the manufacturer that a certain factor can be applied. If a piece of equipment is rated for 16kW, you size the cable for that. You'd usually only apply diversity to sub mains.

 

[JohnD]

Why are people seemingly questioning the competence of the electrician?

Because that's how domestic cooker circuits are calculated.

 

[cam1989]

Why are people seemingly questioning the competence of the electrician?

Because that's how domestic cooker circuits are calculated.

Ah, of course.

Shows how long it's been since I did any domestic stuff. l

 

[ban-all-sheds]

Because that's how domestic cooker circuits are calculated.

And according to the OSG, so too are cooker circuits in shops, offices, small hotels etc. Different formulae, and no diversity for the 1st appliance, but nevertheless there is the concept of diversity for final circuits.

 

[ban-all-sheds]

He is surely unlikely to have forgotten the principles of diversity, even if he needed to look up the calculation.

If his route in was the EAL DI training then he will not have been introduced to the principles of diversity in the first place.

 

[Barney1686]

Hi, I am not sure what EAL DI training is but I will ask him.

 

[JohnD]

"DI" is Domestic Installer, which is the lowest grade of qualification in Competent Person schemes. I will admit I am surprised that a DI is not expected to know how to calculate a cooker circuit.

 

[EFLImpudence]

Why are people seemingly questioning the competence of the electrician?

Because it would appear that either he does not know what he is doing or he is manufacturing work and expense.

I work in building services design and we would never apply diversity to a final circuit,

Then you, too, are guilty of the above.
How do you rate socket circuits, then?

unless we had it in writing from the manufacturer that a certain factor can be applied.

The OP does have it in writing from the manufacturer.

If a piece of equipment is rated for 16kW, you size the cable for that. You'd usually only apply diversity to sub mains.

Rubbish.
Do you often end up with final circuits larger than the sub-main and/or the main supply cables?

 

[JohnW2]

If a piece of equipment is rated for 16kW, you size the cable for that. You'd usually only apply diversity to sub mains.

Rubbish. Do you often end up with final circuits larger than the sub-main and/or the main supply cables?

Quite so. One thing that people, particularly those who are nervous about the concept of diversity, seem to forget is that a sockets circuit is, in many senses, an extreme case of the concept of diversity. If such a circuit has, say, 20 "13A" socket outlets, do they think that the cable and OPD should be rated for 260A?

Kind Regards, John

 

[Barney1686]

Spoke with Britannia today and they advised me that the cooker will need:

On 6mm t&e a 40amp breaker

On 10mm t&e a 45amp breaker

They also said it will be fine using the same consumer unit as the rest of the property.

I spoke with Npower and another electrician today, Npower will be fitting a Isolator Switch later this month, but the sparky I spoke to said as I have a switch next to the 100amp fuse that kills the power I do not need another one.

Will post a picture so you guys can see but im starting to get confused on what I do and do not need.

 

[Barney1686]

Hopefully someone may be able to tell me if I do indeed need an isolation switch fitted or if what is there is in fact ok.

Many thanks guys

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• Barney1686
• 17 Nov 2014
• 1

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• Barney1686
• 17 Nov 2014
• 1

 

[JohnW2]

Spoke with Britannia today and they advised me that the cooker will need:
On 6mm t&e a 40amp breaker
On 10mm t&e a 45amp breaker

That's slightly silly. If a 40A breaker is adequate (which it is) then there would be no need to have a 45A breaker just because the cable was larger. In fact, provided 'de-rating' was not required (because of being buried insulation etc.), a 45A one would be OK with 6mm² cable. If there are no de-rating' issues, then either 6mm² or 10mm² cable on either a 40A or 45A breaker would be acceptable - i.e. as has been said, 6mm²/40A would be adequate.

They also said it will be fine using the same consumer unit as the rest of the property.

Quite so!

I spoke with Npower and another electrician today, Npower will be fitting a Isolator Switch later this month, but the sparky I spoke to said as I have a switch next to the 100amp fuse that kills the power I do not need another one. ... Will post a picture so you guys can see but im starting to get confused on what I do and do not need.

I'm a bit confused, too - as you suggest, I think we need to see a picture of this "switch next to the 100A fuse" to understand what is being said!

Kind Regards, John

 

[JohnW2]

Hopefully someone may be able to tell me if I do indeed need an isolation switch fitted or if what is there is in fact ok.

Ooooh - I think we may have some problems here. I think that black 'switch' is probably a voltage-operated earth-leakage circuit breaker (a very old predecessor of an RCD). If so, it needs to go, and probably to be replaced with an RCD. Did your 'electrician' not comment on that - or did he think it is just a switch? Does your electrical installation have an 'earth rod' outside?

I also fear that your (equally old) consumer unit may well not be suitable for a 40A/45A MCB. Rather than needing a separate additional CU for the cooker, it could be that you need a new (single!) CU for everything, including the cooker.

I'll be interested to hear what others have to say.

Kind Regards, John

 

[Barney1686]

We will be getting a brand new consumer unit john, we would never keep that old thing.

Yes the earth is staked outside, but we are running 2 10mm earth cables in for that.

 

[ban-all-sheds]

That old voltage-operated earth leakage circuit breaker will definitely do duty as an isolator. But you'll only need an isolator once the CU is replaced, so if Npower are going to fit a new one for free, then go for it - you don't want the old breaker going wrong.

He wants to replace my current 6 way consumer unit for a 21 way consumer unit, but im only adding 7 more circuits

Bear in mind that some people count the total number of positions in a CU, not just the ones with MCBs in, so if the CU has a main switch and 2 RCDs then it would be left with 15 ways for circuits. And 6 + 7 = 13, so depending on what your electrician means, a 21-way CU might not be overkill at all.

However - did he say where he was going to install it?

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• Barney1686
• 17 Nov 2014
• 1