Installing oven

[GB]

I've just installed a single oven. The previous one had a 13 amp plug, so I simply wired up the new oven the same way. It's a single oven, with "Energy consumption 0.79 kWh", which doesn't seem too high for a 13 amp plug.

What concerned me is that the manual that came with it said it should be wired to a DPDT switch, direct from the consumer unit, and fused with a maximum of 30A. (**See below for verbatim wording.) That would mean rewiring the kitchen and probably replacing the consumer board to provide the extra connection. It seems overly specified, and I wondered whether they cut and paste the same stuff into all their oven manuals, whether they are low end single ovens or high end double ones?

It's this oven here.

Am I misunderstanding what's required? Does it really require a dedicated cable? It would be pretty easy just to break into the ring main and put in an oven connection with a DPDT switch.

Any help gratefully received.

** "An approved suitable cable must be connected from the Consumer Unit (main fuse box)and be protected by its own 30 amp fuse or Micro Circuit Breaker (MCB). The electrician must provide a fused double-pole isolation switch, which disconnects both the line (live) and neutral conductors, with a contact separation of at least 3 mm incorporated into the fixed wiring. The fused switch should be fitted to the kitchen wall, and must be placed in an easy accessible position in accordance with IEE regulations. Connect the fused switch to a junction box which should be fitted on the wall. The ovens power supply cable can then be connected. Connect one end to the junction box and connect the other end to the ovens power connection box which is located at the back of the oven. Remove the cover of the power connection box and install the cable, in accordance with the connection diagram. The power supply cable must be positioned away from direct heat sources. It should not be subjected to a temperature rise of more than 50°C above room temperature."

[ARW]

You might be at home to Mr Cockup on this one.

The 0.79 kWh is some sort of bollocks that that is used by the manufacturer to represent the average use per cycle of the oven and has f*ck all to do with the maximum electrical load.

[Graham.]

It's a single oven, with

A mobile phone charger will consume that much energy if you leave it switched on for long enough.

It's the power consumption in Watts you need.

[tabbypurr]

There's no power rating in the specs so we can't know. Look on the oven's r ating plate and tell us. If it is a 30A oven, just get a suitable 13A or le ss (3.1kW max) oven instead.

NT

[Graham.]

10SpecificationsModelCBCONW12 / CBCONX12Rated Voltage230-240V Rated Frequency50 Hz Power2600-2800 W Current11 ? 12 A Top Element1200 W Bottom Element1100 W Grill1400/2600 W Net Weight30.2 kg Product Dimensions59.5 (W) x 59 (H) x 57 (D) cm Usable Oven Capacity61 Litres Energy Efficiency ClassA

So as far as I can see you can use your existing circuit, but I personally would replace the socket with an FCU and hardwire it in.

Lets see what Adam says.

[John Rumm]

Alas that does not tell you much of use directly, however the manual seems to indicate that it can draw up to 2800W, which will be ok on a plug (although would be better on a proper flex outlet).

Note it says fused at a *maximum* of 30A - it does not specify the actual required minimum.

They may be assuming you will be powering a hob from the same circuit.

(its also a bit daft since many cooker circuits will be protected by a

32A MCB)

[Tim Watts]

From the manual:

"Power 2600-2800 W"

So a 16A direct circuit would be satisfactory. Technically it *could* be plugged in on a 13A plug but that would not be so recommended. Can't see anything wrong with a 13A spur though, with DP isolator (ie switched fused spur).

Especially as it will not draw that power level for long, once it's heated up and cycling.

[tabbypurr]

OK on a 13A plug then.

NT

[The Natural Philosopher]

Irrelevant.

What counts is the peak power.

I.e. what happens when you switch on everything?

The point here is whether or not all these can be put on together. If they can they will blow 13A fuses.

Only if it is not physically possivle to have grill top and bottom elements all on at once.

[Harry Bloomfield]

Graham. submitted this idea :

A plug and socket provides a much safer/ more certain means of isolation for servicing, than a DP switch. As it needs to draw close to the maximum capability of a 13amp socket, both plug and socket need to be good quality items.

[Mike Clarke]

The maximum current at 2800W would be 2800/240 = 11.67A which would be OK on a 13A plug.

Which makes 4900W maximum if everything was full on, drawing 20.4A.

But the guideline for diversity is to take the first 10A plus 30% of the rest which gives 13.1A.

You'd get away with that on a 13A plug unless you have a lot of other high powered things on the same ring circuit. But as said elsewhere, make sure the plug and socket are decent quality.

[Mike Clarke]

On 19/11/2016 22:09, Graham. wrote this extract from the manual for an oven:

Looks like a distinct lack of joined up thinking there. If the oven really *needs* a 30A fused circuit then there's no need for a second 30A fuse in the switch beside the oven. They don't say what rating the fused switch should be but the only domestic fused double pole switch you're likely to come across is a 13A FCU, implying that it should also be OK on a 13A socket.

If you use a plug and socket instead of a FCU then it would be worth using an *unswitched* socket. Not all switch sockets are double pole and they might not provide a 3mm separation gap. Unplugging before working on the oven will ensure total isolation.

The only reason I could see the need for a dedicated 30A supply would be if you were running the oven and a hob off the same circuit. If you were connecting the hob directly to the main cooker switch then you'd need to use a heavy 30A cable from the main cooker switch unless you used a 13A FCU.

[GB]

I have checked the oven's function controller. Page 5 of the manual, if interested.

It is possible to have top and bottom elements on together = 2300W It is possible to have grill and top element on together. I assume the grill is actually 1400W, and the higher figure shown of 2600W is the top element and grill combined.

So, that's a maximum of 10.8A.

As far as isolation is concerned, it's only possible to disconnect the plug once the oven has been removed from the kitchen unit. OTOH, it's easy enough to switch the ring main off, or even the whole supply. Exactly the same would apply to a FCU in the same location.

Thanks very much, everyone.

[tabbypurr]

13.1A for limited time would be ok on a plug. 20A would not. Try some plugs & see if you think otherwise.

NT

[Roger Hayter]

In practice the grill function and the oven function are likely to share the same elements, so not simultaneously usable.

[DerbyBorn]

Surely the top element is the grill element.

Mine has a knob to select Oven or Grill.

[Mike Clarke]

But diversity considerations mean that it won't draw 20A for sufficient time to be a problem.

[tabbypurr]

Try it or don't.

[John Rumm]

Ideally there should be a accessible isolation switch within 2m of the cooking appliance that can be reached without moving the appliance. So a cooker switch above the worktop or in an adjacent cupboard usually suffices.

Note that switching off the circuit does not usually truly isolate it, since the neutral will still be connected.

[John Rumm]

The range is probably a reflection of the 2800W figure only being achievable with a true 240V...

I would expect since they quote a power figure, that would be the actual highest achievable (i.e. not all elements can be run at the same time due to interlocks)