Cooker circuit

[antgel]

Hi all,

Thanks to all your help, I've finished the lighting in my lounge and kitchen, and everything works well.

I'm moving onto the kitchen electrics now. I'm buying a built-in oven and a built-in microwave, both of which have plugs on. Is it okay to run an unswitched double socket from the cooker switch? I'm sure that the microwave would work on the normal ring, but for convenience I'd like to plug it into the cooker circuit this way.

Also, am I allowed to wire a hob from another unswitched socket wired from the cooker switch? I suppose this would be like having two spurs from the one switch which I know is not allowed on rings, but I'm not sure about radials. It would be fantastic to be able to switch all three appliances on and off via the single switch.

Antony

[Andrew Gabriel]

Providing there's no wired-in cooker on it anymore, then yes, you can effectively turn it into a 20A or 30A radial circuit. If the circuit is protected at more than 30A (fuse or MCB), then reduce the protection to 30A max.

Yes, that's fine too.

[antgel]

The current MCB for the cooker circuit is 15A. Is this likely to be enough to power an oven, microwave, and hob? I can't uprate it as my CU can only take 100A max. If it's going to be a problem, I suppose I'll have to have to put the microwave and hob on the normal ring.

Antony

[Andrew Gabriel]

Add up the power ratings of the appliances. (I'm assuming the Hob is just a spark ignitor on a gas hob, and not an electric hob.) If the power rating totals more than 3450W, then 15A isn't enough.

BTW, the 100A max on the CU is the max current load, not the max total of all the breakers. There are a set of diversity guidelines in the IEE On-Site Guide which give guidance on how much the total MCB ratings can exceed the 100A value, given that many circuits are unlikely to be operating at max load all the time.

Also, before uprating the fuse, you will need to check the circuit is still properly protected by a higher current fuse. This would be governed by the size of cable conductors, the length of the cable run, and if the cable passes through any thermal insulation or warm areas.

[antgel]

No, it is an electric hob.

Interesting. Infact, disregarding that, as I'm installing a combi and ditching the hot water cylinder, I could uprate the cooker circuit to

30A if necessary, as the 15A immersion circuit will no longer be needed.

Indeed.

[Andrew Gabriel]

OK, forget what I wrote before.

What's the power rating of: The hob, The oven, The microwave?

Electric hobs can't normally run on a 15A circuit to start with.

[antgel]

Oven => 2.3 Hob => 6.3 Micro => 1.9 or 3 depending on whether I go for the one with the conventional oven built-in.

This totals 10.5 or 11.6. Is 30A enough for this? I don't think so, if your calculation before is anything to go by.

[Andrew Gabriel]

The hob will need wiring in to a dedicated 30A circuit. The other two could go on a second 30A radial circuit.

[kev]

Oven => 2.3 Hob => 6.3 Micro => 1.9 or 3 depending on whether I go for the one with the conventional oven built-in.

This totals 10.5 or 11.6. Is 30A enough for this? I don't think so, if your calculation before is anything to go by.

Doesn't the '10A + 30% of remainder, plus 5A if outlet fitted with a socket' diversity formula apply?

If so, it's about 19.2 amps for the hob/oven.

The microwave is either 8.2 or 13A, but would be permissible if plugged into a socket on a cooker switch/socket unit.