new oven and hob

[Scoby_Beasley]

Just got possesion of new Zanussi built in oven and ceramic hob. Reading the instructions the hob (at max) is 5.8kw !!!(oven 2.1kw).
Now the 6mm2 cable will take it but should I fit a 32amp mcb instead of the 20amp that I've always used before ?? (I know the 5.8 is max draw but don't want to bugger up next Xmas dinner, I didn't realise separate hobs could draw so much, it's got more power than the old shower I'm going to remove )

 

[BR]

Simply upgrading the breaker to a 32A shouldn’t be a problem, but inspect the circuit/wiring first.

 

[securespark]

Scoby

Treat the two appliances as if they were one, and apply diversity : for the formula, search elsewhere in this forum.

Total load= 34.3A

Take 1st 10A=10A

+ 30% of remainder= 7.29A

+ 5A if you have s/o incorporated in CCU. (figs calced at 230V)

So in this case, your loading (with diversity) would be 22.29A.

 

[Big_Spark]

Secure, I hate to burst your bubble, but applying diversity to a circuit of this nature is not advisable.

There is a reasonable chance that at some point all the full load of the two appliances will be used.

The combined total of both appliances is 7.9kW, which is 34 A, so fitting a 32A MCB will likely not be enough for the total potential load of the circuit.

This being the case he should fit a 40A Type 2 MCB, preferably a 40A 32mA RCBO for greater protection.

Now I know some of you may hark on about diversity, but Reg 311-01-01 states:

The maximum demand of an installation, expressed in amperes, shall be assessed. In determining the maximum demand of an installation or part thereof, diversity may be taken into account

You see it says may be taken in to account, but does not state it will do in every case.

Due to the erratic way in which people will use cooking appliances, I think it is wiser and safer to assume that they will use the full potential load of the device(s) connected to that circuit.

Diversity is great for ring mains and certain other types of circuit, such as sub-mains etc, however cooking circuits should not be one.

 

[Scoby_Beasley]

Simply upgrading the breaker to a 32A shouldn’t be a problem, but inspect the circuit/wiring first.

New cable inserted ready for this (6mm2). You know what its like, SWMBO never wants the new appliance(s) where the old one was

 

[Scoby_Beasley]

This being the case he should fit a 40A Type 2 MCB.

I bought one by mistake 3 months ago, well not by mistake but I buy the bits to suit a certain shower then they come home with a different one!!
I think I'll put it down to forethought and advanced wisdom, not a bloody c**k up!! One step in front of SWMBO for once
Also, SWMBO and cooking go together like rhubarb n baked beans (don't tell me someone likes that !!) so full power probably (I say probably) low down.

 

[securespark]

Beg to differ FWL. You're not bursting my bubble, don't worry.

Cookers often have diversity applied to them. If you were to install an all-in-one cooker, you would apply diversity, otherwise you might end up having to cater for 12K's of load, which is impractical. There is no reason why a hob & oven cannot be treated in the same way, not at all. The whole point about diversity is that in a domestic sitn it is unlikely that f.l. will be applied to the circuit.

 

[AdamW]

There is no reason why a hob & oven cannot be treated in the same way, not at all.

Obviously you have SWMBO well trained and never have to cook for dinner parties! Whilst it is a once-a-year occurrence, there is a possibility that you might end up using full power with both oven and hob simultaneously (pre-heating an oven to a hot temperature whilst searing some steaks in order to make beef wellington, whilst also heating up some soup for a starter... better stop, I'm drooling )

This is a situation where you shouldn't use diversity. The above situation is likely to happen, diversity should be used for safe assumptions such as not plugging 10 fan heaters in at once.

 

[securespark]

SWMBO??

I do all the cooking, anyhow, but we have a gas hob.

 

[Big_Spark]

Beg to differ FWL. You're not bursting my bubble, don't worry.

Cookers often have diversity applied to them. If you were to install an all-in-one cooker, you would apply diversity, otherwise you might end up having to cater for 12K's of load, which is impractical. There is no reason why a hob & oven cannot be treated in the same way, not at all. The whole point about diversity is that in a domestic sitn it is unlikely that f.l. will be applied to the circuit.

With respect Secure, I am the youngest of 7, and my mother had an electric cooker for about 2 years..dad thought new technology was the way forward...Mum agreed, just not in the kitchen..anyway, the point is, cooking a meal for 9 hungry souls would often result in the full load of the cooker being used on a couple of occasions a month..this used to blow a fuse until my dad got a sparky in to sort it out.

So you see, whilst many families may not find themselves in this situation, there is a reasonable bet that the cooking appliance will be used in excess of 90% full potential at some point within a given 12 month period. That being the case, diversity is out of the window.

 

[securespark]

So tellm me how you would tackle a 12kW cooker circuit @ 52A??

 

[Big_Spark]

So tellm me how you would tackle a 12kW cooker circuit @ 52A??

Give me the manufacturers details of the cooker, model No, Manufacturer etc and I will gladly supply the details you request.

 

[securespark]

In general, not specifically.