Wiring for Smeg range cooker

[JohnW2]

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

The OP was already aware of the MIs, but nevertheless asked if it might be possible to use the existing 6 mm² cable - and, as far as I can see, electrically speaking, the answer is almost certainly 'yes'.

After application of diversity, Method C 6 mm² cable can serve a cooking appliance 'rated' at about 133 A - about 30.6 kW at 230V, but would probably be sold as a "33.3 kW" cooker (at 240V). I've never personally come across a domestic cooker with even remotely as great an electricity requirement as that ... and remember that that the OP's entire installation may well only have a "80A supply".

Kind regards, John

 

[RandomGrinch]

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

Kind Regards, John

My guess was for the TR103.

My comments earlier were deliberately guarded - given the comments by others.
20kW is tight on diversity, so some may not recommend.

Again, in my non-expert (and possibly pragmatic!) opinion, I personally would use a 10mm flex to connect the range from the cooker outlet. Thus have some plausible deniability with the manufacturers!
I doubt I would ever need to turn 3 ovens and 5 hob zones on at the same time, but I would look into upgrading cabling and MCB, if I did suffer from nuisance trips

 

[markyd1]

John.....absolutely agree with everything you are saying but if the OP rang Smeg and threw all your calcs at them and asked if she could use a 6mm cable they would reply with....We recommend a 10mm cable, this is not about ratings, deratings, thermal effects, loads or size of MCB its about what they recommend

 

[EFLImpudence]

Please may I have a link to the site you are using?

 

[RandomGrinch]

Please may I have a link to the site you are using?

Product page, or was this a request to someone else?

Cooker Cream TR103IP | Smeg.com

Cooker Cream TR103IP: Smeg designed in Italy, has functional characteristics of quality with a design that combines style and high technology. See it at www.smeg.com

www.smeg.com

The connection information page in the manual doesn't quite match that from the OP, so there might still be some room for error.

 

[JohnW2]

My guess was for the TR103.

As I implied, that was also my guess.

My comments earlier were deliberately guarded - given the comments by others. 20kW is tight on diversity, so some may not recommend.

Not really. A cooker sold as "20kW" (almost certainly at 240V) would only draw (a max of) 79.86 A at 230V (about 18.36 kW), which, after diversity, would be 30.96 A - actually well within the capacity of Method C 4mm² cable, let alone 6mm². Even with some other installation method and/or other de-rating factors, 6 mm² would therefore very probably prove (by calculation) to be more than adequate.

Again, in my non-expert (and possibly pragmatic!) opinion, I personally would use a 10mm flex to connect the range from the cooker outlet. Thus have some plausible deniability with the manufacturers!

We (at least I) have been talking about the fixed wiring of the circuit, not the flex connected to the cooker. I'm also a non-expert in the same sense that you are, but I don't think I would go that far (for the fixed wiring). I might use 6 mm², even if my calculations indicated that 4 mm² was sufficient, but I don't think I would even dream of going bigger than 6 mm².

I doubt I would ever need to turn 3 ovens and 5 hob zones on at the same time, but I would look into upgrading cabling and MCB, if I did suffer from nuisance trips

Fair enough but, in reality, it "isn't going to happen". You would never have all the current-using parts of a cooker drawing current simultaneously for appreciable periods of time, and even a 32A MC will allow 46.4 A (and a 40A one will allow 58 A) to flow for an hour, and higher currents than that to flow for shorter periods of time, without tripping.

Kind Regards, John

 

[JohnW2]

John.....absolutely agree with everything you are saying but if the OP rang Smeg and threw all your calcs at them and asked if she could use a 6mm cable they would reply with....We recommend a 10mm cable, this is not about ratings, deratings, thermal effects, loads or size of MCB its about what they recommend

They probably would say that, but that doesn't make it sensible, necessary or even necessarily safe.

They are seemingly being rather silly in implying that 10 mm² cable is necessarily ('always') adequate, without saying anything about installation method or de-rating factors - if buried in insulation and maybe also with other (e.g. 'grouping') de-rating factors, even 10 mm² cable may not be adequate (or 'safe') ! ... if that were the case, 10 mm² cable could have a lower CCC than (Method C) 2.5 mm² cable!

If it were my house, I would be more concerned that the cable could be shown (by calculation) to be adequate/safe than about what the manufacturer might say!

Kind Regards, John

 

[RandomGrinch]

We (at least I) have been talking about the fixed wiring of the circuit, not the flex connected to the cooker. I'm also a non-expert in the same sense that you are, but I don't think I would go that far (for the fixed wiring). I might use 6 mm², even if my calculations indicated that 4 mm² was sufficient, but I don't think I would even dream of going bigger than 6 mm².

Yes, I was also suggesting stay with the 6mm for the fixed wiring - the way I interpret the MI, is it is specifying the cable connection at the ranges terminal blocks - 10mm conforming to:
"Use H05V2V2-F cables withstanding a temperature of at least 90 °C".

I don't see any specific mention of the fixed wiring, other than the vague:
"Check the mains characteristics against the data indicated on the plate"
And:
"The aforementioned power cables are sized taking into account the coincidence factor (in compliance with standard EN 60335-2-6)."

 

[EFLImpudence]

They also say:

but no one ever seems to take any notice of that 'instruction'.

 

[JohnW2]

Yes, I was also suggesting stay with the 6mm for the fixed wiring ...

Fair enough - and, as i said, depending on installation method etc., even 4 mm² might be adequate for the fixed wiring.

- the way I interpret the MI, is it is specifying the cable connection at the ranges terminal blocks - 10mm conforming to:
"Use H05V2V2-F cables withstanding a temperature of at least 90 °C".

That's rather different. The Table (4F3A) for flexible cables in BS7671 only goes up to 4 mm², so I can't be sure what are the CCCs of 6 mm² or 10 mm² flex. However, one one gets above 1.5 mm², the CCCs for flex seem to be only slightly lower than those for Method C T+E of the same size, so I suspect that 6 mm² (flex) would probably be more than adequate.

I don't see any specific mention of the fixed wiring, other than the vague: "Check the mains characteristics against the data indicated on the plate"

Fair enough. I would say that is exactly what we have been doing in our discussions about the (fixed wiring) cables - so, contrary to what marky has been suggesting, maybe we have been 'compliant' with the MIs!

And: "The aforementioned power cables are sized taking into account the coincidence factor (in compliance with standard EN 60335-2-6)."

That "aforementioned" seems to imply that we are back to talking about the flex. If I had some idea of what the "coincidence factor" is, I might be able to comment

Kind Regards, John