Wiring for Smeg range cooker

[EFLImpudence]

That calculator could not find a suitable PVC twin and earth cable for a load greater than 10kW

Perhaps not a very good calculator.

Above 10kW it was suggesting SWA

Why would it do that?

As for diversity, It can be applied to most multi-element appliances in average use but unless the appliance has integral power management a rating based on diversity alone cannot be relied on.

Why not?
Nearly every standard cooker and cooker circuit must fall into that category.

If a 19kW cooker will in reality and due to diversity only be a maximum load of 7kW then why does the manufacturer describe it as a 19kW appliance.

Because they are European and are just adding up the elements?

My dual ring induction hob does have integral power management which prevents both rings being set to full power at the same time.

Why? How much would it be without that?

 

[EFLImpudence]

Bernard:

Are you suggesting that the OP cannot install his cooker without an 80A circuit?

 

[EFLImpudence]

I have just realised that 32A after diversity is 20kW.

I have always had it in my mind that 19kW was the maximum for 32A; and it is 16kW (not 15kW) when allowing for a socket on the cooker switch.

They both seem to have increased by 1kW; where did that (or my previous thinking) come from?

 

[plugwash]

As far as i'm aware the guidelines for diversity on domestic cookers are.

First 10A , plus 30% of the remainder, plus 5A for the socket (if there is one).

Without socket (working to 3 significant figures).

10A + (i-10A) * 0.3 = 32A.

i-10A = 73.3A

i = 83.3A

p = 230V * 83.3A = 19.2KW

With socket.

10A + (i-10A) * 0.3 + 5A = 32A.

i-10A = 56.6A

i = 66.6A

p = 66.6A * 230V = 15.3 kW

 

[bernardgreen]

but I think it is wrong to give the impression that yours is a widely-held or widely-accepted view.

I did not say it was a widely-held or widely-accepted view.

 

[JohnW2]

I have just realised that 32A after diversity is 20kW. .... I have always had it in my mind that 19kW was the maximum for 32A; and it is 16kW (not 15kW) when allowing for a socket on the cooker switch. ... They both seem to have increased by 1kW; where did that (or my previous thinking) come from?

Have you perhaps succumbed to the 230V/140V 'confusion? As I see it ....

An after-diversity current of 32A corresponds to a before-diversity current of 83.33 A (about 19.17 kW at 230V). If there is a socket, the max pre-diversity cooker current would therefore be about 78.33 A (hence about 18.0 kW at 230V).

However, as we always say, those cookers which consume (a max of) 83.33 A and 78.33 A (at 230V) would usually be described by marketing folk as 20.87 kW and 19.62 kW respectively (at 240V).

A cooker sold as "19 kW" (usually at 240V) would draw a max of 75.87 A at 230V, hence about 29.76 A (~6.85 kW) at 230V after diversity.

Is that not all correct?

Kind Regards, John

 

[JohnW2]

I did not say it was a widely-held or widely-accepted view.

You didn't, but unless I'd made the point, other readers of what you'd written may well have interpreted as such.

Without any acknowledgement that it was not a "widely-held or widely-accepted viiew", your statement "a rating based on diversity alone cannot be relied on" sounded fairly authoritative to me, and hence could well have been taken as such by others.

Kind Regards, John

 

[EFLImpudence]

Have you perhaps succumbed to the 230V/240V 'confusion?

Maybe, but I do always say the Wattage is usually quoted for 240V.

As I see it ....
An after-diversity current of 32A corresponds to a before-diversity current of 83.33 A (about 19.17 kW at 230V).

Yes.

If there is a socket, the max pre-diversity cooker current would therefore be about 78.33 A (hence about 18.0 kW at 230V).

You have to subtract the 5A from 32A; not the 83A
So 32A -5A for socket is 27A,
17/0.3 = 56.66+10 = 66.66x240 = 16kW which at 230V would be 15.3kW.

However, as we always say, those cookers which consume (a max of) 83.33 A and 78.33 A (at 230V) would usually be described by marketing folk as 20.87 kW and 19.62 kW respectively (at 240V).

Yes, allowing for the corrected values.

A cooker sold as "19 kW" (usually at 240V) would draw a max of 75.87 A at 230V, hence about 29.76 A (~6.85 kW) at 230V after diversity.

Yes.

 

[JohnW2]

You have to subtract the 5A from 32A; not the 83A ... So 32A -5A for socket is 27A, ... 17/0.3 = 56.66+10 = 66.66x240 = 16kW which at 230V would be 15.3kW.

Yes, sorry, I wasn't thinking straight about that. I must admit that I always have the "19 kW" (without a socket) in my head, and never really think about the 'with socket' situation - so I don't think that (unlike you) I've every really thought about whether it was 15 kW or 16 kW.

Kind Regards, John

 

[markyd1]

So after all that to the OP 10mm

 

[JohnW2]

So after all that to the OP 10mm

Why?

Some entire flats (and maybe even houses) are supplied through 10 mm² cable.

Kind Regards, John

 

[markyd1]

Why?

Some entire flats (and maybe even houses) are supplied through 10 mm² cable.

Kind Regards, John

Manufacturers instructions.........If not followed and appliance gets a fault they will just blame the sparky

 

[JohnW2]

Apologies- it is a TR013IP/G

Are you sure about that? I can find plenty of variants of TR103xxx, but not TR013xxx.

Kind Regards, John

 

[EFLImpudence]

Manufacturers instructions.........If not followed and appliance gets a fault they will just blame the sparky

There is no fault that could be caused by using a 6mm² cable rather than a 10mm².

Apart from that 6mm² could carry 47A (if method C) so it could be fitted with a 40A or 45A MCB.

Are you suggesting a 10mm² cable and 63A MCB?
Although even that is not big enough if it is thought that the circuit must be able to carry the 80A+ of the cooker's total Wattages.
If not, then it is just a matter of what level of diversity is acceptable.


What rating of MCB do the manufacturers state should be used?

 

[markyd1]

They are not recommending a MCB, they are recommending a 10mm cable. And it wont matter what the fault is they will say not fitted to manufacturers instructions.....End of