Advice needed - Cooker Cable

[JordanBlack]

Hi everyone,

Just after a little bit of advice. we got an electric hob and oven and the total Kw is 11kw.

Now would this be ok with 6mm and on a 40amp mcb?

The cable run is approx 15m

Thanks

 

[stem]

Here's a useful cable size calculator

http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

For cookers, diversity is allowed as you will never be taking the full load at any moment in time, even if everything was switched on, the thermostats will be cutting the various elements in and out.

From my college days (This was some time ago, so someone else may advise if this information is out of date) Calculate the current required by the full load 11000(w)/230(V) =48A

Of the 48A, you take the first 10A and add 30% of the remainder to give you the figure allowing for diversity, which I reckon is 22A,

If there's a socket on the cooker switch add another 5A = 27A so a 32A supply will be sufficient.

So, enter the figures in the table referenced above to see if you will be OK with 6mm cable (You don't state the installation method of the cable which will have an effect)

6mm cable would be too small to be protected by a 40A MCB

 

[ban-all-sheds]

Another guide to cable size calculation, with a bit more detail on the why's & wherefore's...


http://www.kevinboone.com/cableselection_web.html

 

[ericmark]

With induction hobs be very careful with diversity as they have a boost so two or four rings take same power and I would not allow diversity with induction hobs as a result.

 

[ban-all-sheds]

Surely the rating (not the useless kWh one) must take into account any boost function, and give the maximum load?

 

[ericmark]

Sorry maybe I did not explain fully.
With any other hob than a induction you will have possible 4 rings and even if all 4 are used together the simmer controls will normally reduced to total and although you may get peaks with full power being used supplying a 9Kw (39 amps) with a 32 amp supply would be very unlikely to cause problems.
However with the induction hob when one ring is not used extra power is used with other ring/s so unlike the normal hob as simmerstat cuts in there will be no reduction in current as extra will then be used by other rings.
So if the plate says 9Kw that is what it needs and supplying 7.36Kw is no good.
More integrated but similar idea to old baby belling with 2 rings, grill and oven all on 13 amp plug. Selector switch was used with these.

So it basically allows you to use 4 x 4.5Kw rings but automatically reduces total to 9Kw.

Hence how it can heat up food faster than gas.

So a 9kw induction hob will need a 40amp MCB not a 32amp MCB as you can't allow any diversity.

I am not sure if MCB is allowed from what I have read some require a semi-conductor fuse in line rather than MCB as on short circuit MCB's are too slow. But when I tried to verify this on manufactures web sites I could not find anything to say fuses not MCB's should be used so maybe there are fuses built into the unit? I think it is a little off that you have to buy one before one can read installation instructions at that point a little late to find it needs new cable etc.

Shortly my mother is to have one fitted because she is unstable on one leg and often has to save herself with her hands and we were worried about her supporting herself in an emergency on the hot hob. With induction although you can still burn oneself the temperatures on the hob are lower so less damage and do things like auto switch off when pan is removed. As a result I have been taking an interest although she has to pay for new hob it is all fitted FOC because she only has one leg and I know the existing supply is only 32A and I have been trying to find out what they intend to do as far as up-grading the electrical system.

Hence why I have looked into these systems.