SEPERATE CU SUPPLYING KITCHEN APPLIANCES

[sh]

I am using a 4 way cu to supply Single oven/Microwave combi/Hob in a newly fitted kitchen.This is being fed from the main rcd controlled cu.The mcb's are 16/16/32 amp respectively.What size mcb do I need to use from the main cu to supply the secondary one.
Thanks

 

[alertelec]

What cable is supplying the 4 way consumer unit? You also need to find out what the maximum MCB size is available for your main consumer unit.

You have a total load of 64amps that could possibly be used at once but that is the level of over current protection rather than maximum load.

If you have 10mm T&E cable or larger fitted already then you can fit up to a maximum of a 60amp MCB.

I'd appreciate it if a Sparks could confirm this post. Also I don't think that diversity should be taken in to account here?

 

[plugwash]

if its 10mm cable then i would use a 50A mcb (the next size a 63A would be pushign things a bit with the cable rating and i don't think you need it)

if its 6mm the maximum you can use is a 45A mcb

also if there is any form of switch (like a cooker control unit) before the 4 ways CU then you shouldn't use a breaker above the rating of the switch

it is certainly reasonable to apply some diversity to a cuircuit like this. wether it is reasonable to apply as much as the regs allow for is another matter.

what are the actual power ratings of the individual items?

 

[sh]

It is 10mm from the main cu to the secondary one.
The power ratings are Hob-6.8kw / Oven 3.5kw / Microwave 3.6kw

 

[plugwash]

13.9KW total
at 230V
60.43A
using the cooker diversity guidelines from the wiring regs (assuming no socket)
10+(50.43*.3)=25.13A
now most people here would probablly agree that the diversity guidelines for cooker cuircuits go a bit too far but i can't realistically see you haveing any trouble with a 45A or 50A cuircuit

 

[securespark]

What about discrimination?

 

[plugwash]

discrimination is a sick joke in current domestic wiring anyway with the prevalence of mcbs and rcds.

we happilly put our rings on 32A breakers which in a low loop impedence situation will trip long before a plug fuse will!

and we put a single rcd covering all the sockets in the house all the time without a second thought!

how much does it really matter if in the event of one of the cooking appliances having a very serious fault it knocks out the other two for a couple of minuites? i would consider this a much smaller inconviniance than having a portable appliance fault knock off the ring with my PC on it.