built in electric oven and microwave

4 Aug 2004
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United Kingdom
We are about to install a new cooker unit and separate microwave. We have removed the old double oven unit and have found that the connection is direct into the cooker from the cooker point( isolating switch). So, now the problem part.

We have bought a Neff B1451 single oven unit with a rating of 2.8kw( no cable or plug) and a Neff B77409 Quantum speed microwave combi oven with a rating of 3.6kw (has a standard 3pin plug attached). Both units in the instructions say they must have an isolation switch. Presumably the oven has a similar connection system to the one we disconnected from the old oven. (We haven't looked yet as the oven is still in the packaging)

So, how do we connect both units?

We assume we can wire into the back of the oven and use existing switch. But the microwave is the problem, we assumed this would be plugged into a 13A socket but the loading for the microwave is 3.6Kw.

Help :eek:
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seem a lot for a microwave
most micos are no more than 900w plus any heating element
if they are a combination oven

now if its factory fitted with a plug it should be ok
but dont take my word for it phone the manufacturer

perhaps if you add up all the functions working at one time
they would add up to 3.6
but shurely you can only use 1 or 2 at a time
and not all the functions

big all
:confused: Having taken note of the comment about microwave ratings being normally 900 kw we decided to check the appliance itself for any information, our original data being taken from the Neff catalogue.

Having never before taken the unit completely out of the box imagine our surprise to find that there wasn’t a plug on the end of the connection cable, just some small connectors. This was in contradiction to the instruction book and the installation guide that come with the unit.

Anyway, we checked the specifications and found that although there are differences between the catalogue, instruction book and the fixed plate on the unit they all point to the output as being somewhere in the region of 3.1 to 3.8 kw. So, we contacted Neff about this and were informed that the information about the plug only applied to the German version, and that the microwave had to be "Hard Wired" into a connection box. So we looked again at the connections in our kitchen.

Our first thought was, can we wire the microwave and built in oven together from the same connection box? On some investigation we found that the original double oven and the hob (even though they are on opposite sides on the kitchen are wired together ie consumer unit (via 30A mcb) to the cooker control switch for the oven and then up over the ceiling to another cooker control switch for the hob.

can the new single oven and microwave be wired into the same cooker control switch together along with the hob on the other side or do we need a totally new route from the fuse box for the microwave?

The ratings for the appliances are oven 2.8kw, microwave 3.6kw and hob 6.6kw making a total of 13kw.

what breaker and cable is your existing cooker cuircuit on?
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Note quite up to the jargon, breaker being the amp size. I assume its a 30 amp circuit as the spot on the mcb is blue. How do I check this?

As for the cable, I'm not sure how you measure it but its flat rectangular grey stuff, three core. its about 10mm by 5mm.

None of this was put in by us but by the previous owners at some time.

Thanks in anticipation.
colored spotds on mcbs?!

can you get use a picture of your condsumer unit (fuse box/breaker box in old terms)
Sorry the spot was red!

I can get a picture but will I suppose have to send it to the admin team.

Is this what you need?
Isn't red the traditional colour for 30A? Pateman - if you have circuit breakers and not fuses, there should be writing on them to identify the ratings. You can upload the picture at http://imagehost.darkernet.co.uk, and then reference the URL in a post here.

And 10mm x 5mm external dimensions sounds like 2.5mm to me, which is too small for 30A....

A 13kW load is 56.5A, and to support that you'd need 16mm cable on a 63A breaker. If it were a single cooking appliance, you could use the conventional rules of 10A + 30% of the remainder to get to a 24A load, which would mean a 30A breaker and 6mm cable (possibly 4mm), although this is widely regarded as a daft rule

Also this is 3 appliances, not 1, and if you calculate each one individually and add them up you get to 38A.

10mm/50A sounds like a workable design, but

a) Multiple cooking appliances on one circuit are frowned on (don't think they actually contravene the regs though)

b) You will really struggle to get two 10mm cables into the first CCU.

I think in reality you're going to need 2 circuits, one for the oven and microwave, one for the hob.
i am still confused is it a commercial HEAVY DUTY combi microwave
14 amps for a micro wow what functions has it got
its unusual to get a jaccosie microwave :D :D :D :D

big all
pateman said:
Neff B77409 Quantum speed microwave combi oven with a rating of 3.6kw

sounds like his "microwave" is a combi

anyway i think a photo of your consumer unit is in order
From description, the mcb's are the old push button Wylex plug in type that replace rewireable fuses.

Colours and their respective currents, when applied to protective devices in consumer units:

5/6A White
10A Grey
15/16A Blue
20A Yellow
30/32A Red
35/40A Orange
45A Green

Glad you said 30A, as blue is 15/16A....!
since they are on opposite sides of the kitchen i would say 2 seperate cuircuits are in order

each cuircuit rated at 30/32A using 6mm cable

the hob cuircuit would be wired to a cooker control unit and a cooker outlet in the normal way

the oven and microwave cuircuit would be wired through a cooker control unit and then into a small 2 way consumer unit with a 16A breaker for each
ok can you confirm that the circle with text at the top of the breakers says wylex?

also are all those breakers actually used?

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