Double oven and electric hob wiring

[Zebsport]

Hi,
We've just purchased a built under double oven (max 4800w) and a electric ceramic hob (max 6500w). The original freestanding electric cooker and hob has been running using the usual 6mm cooker cable, but surely this can't be right. With the new max being a possible 11300w then would I need an increase in cable size?
Any help would be much appreciated.

Zeb

 

[GaryMo]

with regards to maximum current drawn - it depends if you want to design the circuit with full load in mind or with diversity.

I would personally run a 6mm2 twin and earth to each unit but others will argue that if the double oven had the hob attached thus making it one unit would then a single 32A circuit would be fine (diversity in mind).

 

[Zebsport]

Thanks. I'm struggling with the whole full load or diversity thing. Maybe xmas day it would get near full load, but do i start knocking around a newly renovated house to put an extra 6mm cable in, for that very rare occasion. But then again i don't want to be eating my xmas pudding on the pavement cause my house has burnt down!!!

 

[kevindgas]

11300 / 230 = 49.13amp

i certainly wouldn't want to run that on a single 32A radial! given that a ring would at least share the load

but most cooker circuits are 40amp on 10mm cable to the conection box

then run in smaller cable to each appliance as per manufacturers instructions

 

[GaryMo]

but most cooker circuits are 40amp on 10mm cable to the conection box

No, most domestic cooker circuits are 32A circuits with 6mm2 cable.....in my experience anyway.

 

[Steve]

Most NEW cooker circuits are on 10mm with 32 or 40 amp protection.

 

[GaryMo]

Most NEW cooker circuits are on 10mm with 32 or 40 amp protection.

Survey results?
I would still err on the side of 32A and 6mm though

 

[equitum]

11300 / 230 = 49.13amp

i certainly wouldn't want to run that on a single 32A radial! given that a ring would at least share the load

but most cooker circuits are 40amp on 10mm cable to the conection box

then run in smaller cable to each appliance as per manufacturers instructions

Tosh !

Applying diversity:

(domestic cooking appliance = 10A + 30% of remaing full load + 5A if a socket out included in CCU)

1st Appliance : 10 + (((6500/230) -10) x30%) = 15.48A
2nd Appliance : 10 + (((4800/230) -10) x30%) = 13.26A

Total design current = 28.74A

32A breaker sufficient, unless you include a socket then 40A required.

And I don't believe in the christams day scaremongers, cooking elements are thermostatically controlled, thats why diversity is allowed.

 

[ericmark]

equitum comments on diversity do make sense with one exception.
Induction Hobs
Unlike the normal hob where 4 independent simmerstat controlled hobs are used each a 3kw or less the induction hob will allow one ring to boost the output when it's pair does not require power. The hobs will normally have a maximum power rating which is below the sum of all rings and is the maximum the electronics will permit.

With induction hobs no diversity should be allowed on the maximum current shown on the plate. As the electronics can maintain this maximum for an extended time in comparison with old simmerstat controlled thermal hobs.

As to cable and MCB size it has been 6mm and 30/32 amps for many years my parents house which had a cooker supply added in 1960's was 30 now 32 amp and considering the number already with this size it will be many years before 40 amp could be considered as the norm or average.

And I do wonder about new houses with 40 amp on hob and 16 amp on oven with 45 amp on each of two showers and 32 amp on each of two ring mains plus lighting etc. Going by rule book a 100 amp supply is not enough yet we all know from experience that a 80 amp incoming fuse rarely blows.

So in spite of what I have said about induction hobs this is based on the specifications and in real terms it is likely that a pan will boil so quickly that although it's current draw exceeds the theoretical maximum in practice it may not be a problem.

The same applies to showers I have seen many showers running on a MCB which is too small but it never trips out when a male is using shower!