Replacing single oven with higher power one.

[nellyboy]

Need to replace my 7 year old Bosch single oven (2.85kw). At the moment its connected via a 13amp conventional socket behind the cooker (under the worktop). This is wired up to the kitchen circuit that the hob is on (if I turn the cooker master off it turns the hob and oven off).

My query which I hope somebody can answer is if I decide to go for an oven with a higher load that requires 16 or 20 amps is it a simple case of getting somebody to hardwire the cooker into the current outlet (ie replace the 3 pin socket) or will more work need to be done. Thanks.

 

[PrenticeBoyofDerry]

It could well be a simple case of installing an outlet plate behind the oven to hard wire to.
But things will need to be calculated, a fuse change maybe needed and your cables upgraded.
Do you know the size (csa) of the existing cable, the length of the run and whether it is run through thermal insulation and the type (BS number) and rating (amp) of protective device/breaker/fuse.
It would also be helpfully if you know the output of the oven and the output of the hob.
You say the kitchen circuit, does this mean that all the socket outlets including the CCU (cooker control unit/switch) and outlet socket and connection for oven/hob are on the same circuit?

 

[ban-all-sheds]

And the somebody needs to be registered, as the work would be notifiable.

 

[PrinceofDarkness]

As I understand this, Derryboy: The O/P has a separate (30/32A) circuit for the hob which is likely to be around 6kW - and the existing oven is also sharing this circuit by way of a socket outlet connected to that cooker control switch. I don't suppose either hob or oven to be on the socket circuit.

If this is indeed the case, the O/P is quite at liberty to connect a higher powered oven to that circuit - I doubt that it'll be much in excess of 4kW. He merely has to lose the 13A socket, and use a common cooker connector for the hob and oven.

I don't agree with Banish-all-Sheds that this is Notifiable Work. This is a simple oven change, and as such, is quite allowable under those 'P' rules.

'Nellyboy', if you need further advice, I'd be pleased to oblige.



Lucia.

 

[PrenticeBoyofDerry]

As I understand this, Derryboy: The O/P has a separate (30/32A) circuit for the hob which is likely to be around 6kW - and the existing oven is also sharing this circuit by way of a socket outlet connected to that cooker control switch. I don't suppose either hob or oven to be on the socket circuit.

That's what I was trying to establish by my post, with nellyboy stating kitchen circuit rather than cooker/oven/hob circuit it has thrown me.
We will wait for a reply from OP to confirm the situation.

'Nellyboy', I'd be pleased to oblige.

I bet you say that to all the boys

 

[nellyboy]

Thanks for the replies so far. Sorry for the confusion about the "kitchen circuit". The circuit containing the 13amp cooker socket is a separate circuit from the other circuits in the kitchen. The breaker controlling this is 32amp. Not sure about the cable length, is it the cable between the cooker point (ie the three pin plug) and the cooker switch that is relevant?

Currently the only thing attached apart from the oven is a 4 ring ceramic hob.

 

[PrenticeBoyofDerry]

It's the overall length of the circuit, CU-Appliance outlet.
This is for voltage drop calculations.
What kw output is the hob?

 

[ajrobb]

Do you know which oven you will be using? Some ovens require 16A or 20A protection. Typically you will need a double-pole isolator with 3mm gap if you don't have a plug. With a bigger oven there is a greater risk of tripping the 32A CB.

 

[nellyboy]

The ovens I'm looking at are all 16amp. I'll measure the cable run as soon as poss, away from home at the mo!

 

[PrinceofDarkness]

ajrobb: Whilst it might be the case that certain oven MI's 'require' 16/20A 'protection', these requirements should be viewed in the context of the manufacturer assuming that his product is used as a stand-alone appliance having no regard for the possibility of the presense of an electric hob.

When the installer applies a little commonsense to such a "Standard 30/32A domestic, cooker circuit", he or she will realise that there's little difference between a separate hob/oven together and a free-standing cooker with oven, grill, four rings etc. So, separate (adjacent) appliances should be regarded in combination as one appliance.

Cooking appliances are notoriously difficult to 'protect' whether by 32, 20 or 16 Amp MCB. This is because the MCB, whatever its rating, has to protect against a single or multiple fault to either element, oven light, time-clock etc.

Therefore, the main consideration here is that of short-circuit protection, since it isn't possible for such a fixed load to be overloaded.

It seems to me that the O/P, Nellyboy, has a standard cooker circuit and as such can easily add a larger oven without fear of exceeding the 15kW limit for such a domestic circuit.


Nellyboy: Don't trouble yourself with circuit length, voltage drop and Notification procedures for a simple domestic circuit. Just get on with it!


Lucia.

 

[cozycats]

Having fitted literally hundreds of ovens, although the manufacturer often state the max demand to be (say) 3.45 kw, when you read the manual it is oven 2.2kw and grill 1.25kw, BUT VERY RARELY can you have both on at the same time. The manufacturers requirements for a 16 amp BREAKER are just that. They do not recognize our quaint 13a plugs.

 

[EFLImpudence]

How many times is it stated that the fuse/breaker is there to protect the cable.

After all a 3A fuse doesn't give much protection to a 40W lamp.

 

[PrinceofDarkness]

Exactly so, Impudence.......

And how can a 32A (or larger) MCB possibly protect a single fault on a 25W oven lamp, or electronic timer, whatever the size of the cooking appliance?

The answer, obviously, is that the MCB is there to protect against short-circuit, since it isn't possible to overload a fixed load such as this.....


Lucia.

 

[nellyboy]

Thanks again for all the replies!