circuit for cooker

[domster]

Hi, im having a circuit put in for an electric oven.(smeg suk92mfx5),and for my piece of mind wish to understand a few things.
Its Nominal power is 4.3kw and a 30Amp power supply is needed. The run of cable is @12m,
will 6mm twin and earth be sufficent?
Why are double pole switches 45Amp if the mcb 32Amp?
Why are wires from back of cooker 2.5mm, if its joining 6mm at connecting box.? Many thanks if you can tell me

 

[oharaf]

Your SMEG will draw at most 19Amps, 6mm should be more than adequate for this.

The large number of modern cookers are now powered through a 13amp plug, yours cannot be as it requires in excess of this and hence the larger cable.

 

[Pensdown]

Hi, im having a circuit put in for an electric oven.(smeg suk92mfx5),and for my piece of mind wish to understand a few things.
Its Nominal power is 4.3kw and a 30Amp power supply is needed.

4300watt/230volts = 18.7amp

So for your particular oven a 20amp supply would be enough. However, because ovens come in all shapes and sizes the norm is to over design just incase the cooker is changed for a bigger model

The run of cable is @12m,
will 6mm twin and earth be sufficent?

Assuming the cable run is in open air (not through insulation) 6mm is fine

Why are double pole switches 45Amp if the mcb 32Amp?

Once again, they're made to cover the complete range of cookers and hob combinations, not just your current model.

Why are wires from back of cooker 2.5mm, if its joining 6mm at connecting box.? Many thanks if you can tell me

2.5mm will handle 18.7amps.

I'll leave diversity to someone else

 

[EdwardCurrent]

Hello,

Allowing for diversity = 12.6A , or 17.6A if cooker switch has a socket outlet.

Cheers


Ed

 

[domster]

Many thanks for answering my questions,much appreciated,
To be honest i still dont understand why its ok for 2.5mm cable to go into 6mm, but i dont have to understand it, just as long as its ok.

 

[stargazer]

To be honest i still dont understand why its ok for 2.5mm cable to go into 6mm, but i dont have to understand it, just as long as its ok.

the mcb 32Amp

I’m not sure that is OK, hopefully one of the sparks will clarify.
The purpose of the MCB is to protect the cable feeding your cooker, and 2.5mm cable is not sufficiently rated for any part of a 32 amp radial circuit, unless further protection such as a FCU is introduced.
Not sure what the regs say, but belts & braces I would wire the whole run in 6mm, or de-rate the breaker.

 

[EdwardCurrent]

Hello,

If your cooker switch does not have a socket outlet, then theoretically< ? allowing for diversity, you could run a 2.5mm cable protected by a 16A mcb. However, if you or future owners wish to install a different cooker then you/they are restricted to the current carrying capacity of 2.5mm cable, if you run a 6 or 10mm then there is plenty more 'scope'.

Ed.

 

[domster]

sorry if im confusing the subject, but just to recap,
the cooker has 2.5mm cable comming out of it that will go into the flush outlet plate, but feeding the outlet plate will be 6mm cable from consumer unit via pole switch. Am i missing something?

 

[EdwardCurrent]

Whoops, maybe it was me that confused the issue .

Your 6mm to 2.5mm set up sounds fine.

Once again sorry.


Ed.

 

[domster]

Not at all,thanks for all the help

 

[freeze101]

sorry if im confusing the subject, but just to recap,
the cooker has 2.5mm cable comming out of it that will go into the flush outlet plate, but feeding the outlet plate will be 6mm cable from consumer unit via pole switch. Am i missing something?

yep you got it does this excellant sketch ring true with your setup ?

Untitled

• freeze101
• 8 Apr 2008
• 1

thanks

 

[Pensdown]

To be honest i still dont understand why its ok for 2.5mm cable to go into 6mm, but i dont have to understand it, just as long as its ok.

the mcb 32Amp

I’m not sure that is OK, hopefully one of the sparks will clarify.
The purpose of the MCB is to protect the cable feeding your cooker, and 2.5mm cable is not sufficiently rated for any part of a 32 amp radial circuit, unless further protection such as a FCU is introduced.
Not sure what the regs say, but belts & braces I would wire the whole run in 6mm, or de-rate the breaker.

Because the cooker is a "fixed" load and it's maximum current draw is less than the max for the cable, the regs do allow the use of a cable with a current carrying capacity less than the protective device.

As long as the cable can handle the fault current it's OK.

 

[stargazer]

Thank you for that clarification, kind sir