Question regarding hob and cooker outlets in Kitchen

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Guys,

Am just doing some decorating and changing some units in my kitchen and have come across something that I can't quite get my head around. I'll do my best to explain this logically.

I'll start by giving some background of how things are set out. The house is approximately 5 years old. The kitchen has electric cooker and induction hob as provided when the house was new. For cooker isolation, there is a switched cooker unit above the worktop with socket outlet. For hob isolation there is a double gang module plate with switches and fuses for the hob and extractor fan.

One of the changes I am making is to add a pan drawer under the cooker. While pulling the oven out, I have discovered that the hob is not connected to the outlet which is isolated by the labelled hob switch, if that makes sense.

Behind the cooker there are 3 outlets. One is a socket which is isolated by the cooker switch, which the cooker is plugged in to. Another is a connection unit for large area cables, also isolated by the cooker switch and has the hob connected to it. The final one is a connection unit isolated by the hob switch.

The two which are isolated by the cooker switch are both supplied with what appears to be at least 6mm2 cable. The feed from the hob switch is by the looks of things 1.5mm2, definitely smaller than 2.5mm2 anyway!

My question is, is this set up acceptable? The cooker is rated at 2.8kW and the hob at 7.2kW (2x 2.2kW rings and 2x 1.2kW rings) so a total of 10kW (which I'm guessing is when everything is on max). Now my knowledge is a bit rusty but I seem to remember that 6mm2 probably wouldn't suffice for 10kW? Am I correct? Is the assumption made that not everything would be on full power at the same time though? The circuit is protected by a 32A RCD. I am certainly thinking that the hob shouldn't be connected to the feed that is 1.5mm2 (or possibly less I'm now thinking looking at it again!).

If everything is actually OK with the current set up, with both cooker and hob connected to the same feed and the labelled hob feed not used, do I need to make it clear that the labelled hob switch does not actually isolate it? I would hope that someone would check it was properly isolated before disconnecting it but you never know.

To add to the situation, the property is going to be rented out in the next few months as I am being posted abroad. I obviously will be getting an electrician in for full inspection and testing but would just like to know if it's worth leaving the cooker out or not until that happens.

I look forward to your views!

Thanks in advance.
 
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Sounds like the unused hob set-up is for the ignition on a gas hob. This would only require a small CSA feed.

If it is not used, re-label the switch.

The induction hob on the other hand, needs a heavy feed.

It is perfectly acceptable to have a hob and oven on the same 6mm2/ 32A feed, using diversity.

What is the total load of the hob and the oven?
 
SP, thanks for the response. Now that you've mentioned the word diversity it's all starting to come creaking back to me!

Now where I am really rusty is the maths. The maximum power of the oven is 2.8kW so would that be 12A at 240V? The maximum of the hob is 7.2kW (I'm guessing this would be when all four rings are at maximum?) so would that be 30A?

Total of 42A which is obviously more than the 32A RCD supplying the circuit. Does the diversity factor allow for this? I'm guessing it must do as it was fitted from new like this. It must be 6mm2 cable, I would've thought if it was 10mm2 it would have a 45A breaker? It certainly doesn't look like 10mm2 anyway!

Thanks again.
 
That will be fine.
Diversity is a method that takes the practical point that most electrical items do not run at 100% of their rated current 100% of the time.
This si especially true of ovens and hobs. These have a thermostat on each ring/oven. The heat is constantly switching on and off to maintain the heat that has been set to cook your soufflé.

The same applies to the value of the fuses in your fuseboard. The electricity company's supply fuse is probably no more than 80amp.

Add up the MCB values.
Cooker @ 32A
3 x ring circuits @32A
Immersion @ 16A
3 x lighting circuits @ 6amp
(maybe more)
That's a total of 130amps.

But you'll never have them all running at max capacity. Otherwise the DNO would be dropping in every day to replace everybody's main fuse.
And they would need 10 times more power stations than the ones we have left!
 
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Gotcha.

Very useful responses, thanks very much guys! I'll make sure I get the old Dymo labeller out and identify which one isolates the hob properly.

Ta again.
 
Although you've grasped the excellent advice given with regards to diversity etc..
You then let yourself down by mentioning the oh so 70's Dymo labeller. Anyone who is hip and wiv it uses a Bro (Brother) these days.
I think as humbrage you ought to suffer at least six months of T2C's soufflé suggestion. And don't do it again.

You naughty boy.
 
Tee hee,

although

Better to have a 70's Dymo label than no label.

Buy THIS If you really want a cutting edge printer!
 
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Ha! Not sure what you old fogeys are talking about! Those old Dymo labellers are far older than me! :p Hopefully I can redeem myself by stating that it is actually a very modern digital one. And just to keep Scoby happy, I think I do have a brother one in the garage somewhere. I am so 'wiv it'.
 

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