Oven/Hob/Hood connections

[ReggieP]

Yes, wire them all into the old cooker circuit. No problems at all > Don't

> use sockets/plugs, but FCUs. Ensure the correct fuses are used. Cooke > hoods > and hobs are sufficiently fixed to not be run off a socket circuit > Indeed, > I run many more appliances off dedicated radial circuits, includin > fridge > freezer, washing machine, tumble dryer and dishwasher. In my case > however, > I decided to run the cooker oven off the main ring, largely becaus > with all > the other fixed appliances offloaded, there is loads of spare capacit > off > it, and only the 2nd oven will be electric. Grill, main oven and ho > are > gas. > > When installing, check the oven rating. It may need to be fused at a > particular level (i.e. 13A, 16A or 20A). Ensure this is done, eithe > using > an FCU (for 13A) or by dropping the MCB to that level. Some will be > perfectly happy at 32A, but if it comes with a conventional plug, yo > MUST > use a 13A FCU (unless instructions specifically allow 16A MCB instead > as > would be the case in a European installation). > > However, even if the oven allows 32A, it is still safer to drop the MC > to > the next value over the sum of the appliances you have installed. (i.e > 13A > for the oven, 3A for the extractor, 0A for the gas hob means you coul > run > off a 16A MCB, which is more likely to trip in a fault condition tha > an > oversized 32A, oven if this would be technically allowed). > > Christian.

Thanks for the information. I think adding 2 FCUs (with labels an indicators) to the cooker circuit is the best way forward. The new ove is rated at 4.8kW, hob 100W and hood 260W so this is all well below th current (all-electric) cooker's rating.

Final questions - should the wiring for the FCUs be 4 sq mm or is 2. sufficient? And presumably the FCUs are connected before the cooke isolator, i.e. the isolator switches only the oven supply?

Cheers

-- ReggieP

[Christian McArdle]

OK, consider reducing the MCB to 25A, as well.

Usually, 2.5mm will be sufficient. Overload protection is provided by the FCU fuse. Only if the earth loop impedence is already exceptionally marginal will live-earth short issues preclude 2.5mm to the FCU, especially for such a short run.

I would be inclined to put the hob after the isolator and the fan before. I suppose I expect the "cooker" isolator to turn off all of the "cooker". I can't imagine the regs say much about it, though.

Christian.

[Stefek Zaba]

Just to be clear - the FCUs are for (1) the cooker hood, and (2) the gas hob's ignition, clock, and similar incidentals, right? While the existing Big Cooker Switch is for your electric oven, yes? (I'm checking because - until I reread your original post - I thought you might be connecting a 4.8kW-peak oven, drawing a peak current of 20A, through an FCU, which would be rated for 13A max.)

For the FCUs, 2.5mmsq will be OK for short lengths, as the loads they supply can't create an overload beyond a 2.5mmsq's capacity, and short-circuit protection will be OK with a 32A MCB. There are assumptions here about the lengths of 2.5mmsq being quite short (a few metres only), and running in 'normal' routing and ambient temperature. The last of those is a bit of a dodgy assumption around cookers, so caution would dictate at least being *sure* of the ambient temp, or going for 4mmsq Just To Be On The Safe Side.

As far as placing the FCUs upstream or downstream of the big 'cooker' switch, either is OK if the labelling is clear. The only confusing - and therefore less-than-definitely-compliant - case is where the big switch is labelled 'cooker' but controls only the oven. Explicit labelling makes things compliant here: in the cooker-sw-does-everything case, 'cooking appliances - oven, gas hob, and hood' would be ideal, while in the oven-only case, the word 'oven' seems the appropriate label ;-)