single and combi oven power query

[seneca]

Hi,
we're about to change our built in double oven and want to replace it with a single oven and a smaller combi oven/microwave. Our double oven is using a cooker point which has a 38amp cable coming directly from the fuse box. Is it ok for this 38amp cable and it's cooker point to feed both the new single and combi oven, or do I need to get it changed? I've heard that the combi/micro take a lot of power and want to be able to run both ovens at the same time. I always assumed that as a double was ok then so should a single and combi together - am I right ? Do I need cooker points or can the existing one be split into two. Need to know if I need to get the electrician in before I go out and buy them, or just get him to connect them up.

 

[EdwardCurrent]

Hello Senca.
Best let your electrician work out all the maximum demand/diversity stuff as he will have the information needed. Otherwise....

Firstly we would need to know the power consumption of your new 'cookers'.

You say that you have a cable that is 'rated' at 38 Amps ? How did you come across this figure ? so we can presume that this cable is protected by a 32A mcb ?? Please confirm .
Length of run and installation methods would be a bonus.
Not being picky, just do not want to mis-advise you.
Regards,
Ed

 

[ban-all-sheds]

You say that you have a cable that is 'rated' at 38 Amps ? How did you come across this figure ?

The same way this guy did?

 

[seneca]

I know it's 38 amps because the chap who fitted it left the coil with about a meter on it in my garage. It says Twin & earth cable - max rating 240volts=38amps on the label.

The cable comes from the fuse box in the garage, it has it's own switch (cooker written on it) and runs 2m in the garage. It then goes straight through the wall into the kitchen to the red buttoned cooker switch. From there it hidden in the wall and comes out a meter further to the back of the oven housing. I reckon 4m length in total - straight from thre fuse box and supplies only the cooker.

I don't know exactly what the rating on the old double oven was, but looking online at a similar model, it's around 6000kw. The 2 new ovens I want to replace it are both 3600 kw each (single oven and combi oven.) That makes 7200kw together, which is more than the old double oven.

Reason I'm asking is, we're getting the walls replastered in a few days, and the electrician is on holiday for another week. I don't want him to come and say he can't use the 38amp cable for the new ovens and I have to get a new cable put in (ruining the new plastering.) I had just assumed that it would be ok, but am now worried he may have to fit a new cable and I will need to have it plastered again!

 

[ban-all-sheds]

I know it's 38 amps because the chap who fitted it left the coil with about a meter on it in my garage. It says Twin & earth cable - max rating 240volts=38amps on the label.

Does it say what size it is?

 

[mikhailfaradayski]

how long has the sparky been on holiday?
where has he gone?
when will he be back?
why didn't you ask him before he went on holiday?
did you note that the cable label says 'max' rating?
how do you know that the cable is installed in such a way as to allow the rating you mention and doesn't need de-rating?

 

[ban-all-sheds]

did you note that the cable label says 'max' rating?

And one which doesn't match any maximum rating in the tables in Appendix 4....

 

[rockdg]

Hi Senca
I have just been through all this with various comments, some useful and helpful and some definetly wrong.
My oven was rated @ 3.8Kw My micro/combie was rated at 3.7kW. a 32AMP supply comes from my main board ( mcb protected ) and is connected to a 45Amp double pole switch. The output of this switch should then be wired using 6mm cable into a a new housing consisting of two 16Amp mcb's. This can be wall mounted inside your tall housing cupboard. (This can easily be made yourself) You then wire each appliance direct to its own 16A supply

Each appliance is now protected.

 

[seneca]

thanks rockdg, you appear to have the same oven/combi oven set up that we are after. So, at the moment the 30amp wire going straight from the main fuse box, to the back of the oven housing (via the red buttoned switch) is ok? My main concern is that the 38 amp cable in the wall is ok and does not need to be changed. What goes on at the fuse box, cooker switch, and the back of the oven hosing I'll let the electrician deal with.
It's just he's getting back a few days after the plastering.

So it is possible to take the single 38amp cable at the back of the housing and convert it to 2 cables, with each going to one of the ovens.
Sorry for all the non technical questions, it's just I'd rather not get someone else in just to take a look and tell me the cable is ok or not.

 

[ban-all-sheds]

Does it say what size it is?

 

[seneca]

There's no mention of size, it only says it's from Wickes - twin & earth max rating at 240volts=38amps 6242yh (suitable for cookers & showers)

I have measured the whole cable and it's quite thick and difficult to bend 14mm x 8mm (how non technical is that - bet i get told off!)

 

[sparkwright]

http://www.wickes.co.uk/6mm2-Twin-and-Earth-Cable-6242YH/invt/156256

 

[Steve]

(how non technical is that - bet i get told off!)

The only thing is, its very dangerous to print 38 amps on the side of a cable reel. Because if a DIYer were to get hold of it, without appropriate knowledge, he may miss the "MAX" bit and assume its capacity is 38 amps all the time. Mightn't he?

Its capacity varies according to its length, how it is installed, the ambient temperature, amongst other things. This is why we refer to cable by CROSS SECTIONAL AREA in mm².

 

[sparkwright]

Sounds like you could do something similar to rockdg.

However, he had to fit separate circuit breakers in cupboards.

Is it possible to run another new cable from the mains (in the garage) to the kitchen?
Is there a spare way in the consumer unit?

If you CAN have two separate circuits for these appliances it would be a better job as you wouldn't have the fusing down problem (though you would have to fit 16 amp [?] breakers at the mains).
You could have individual isolation switches in the kitchen.
If one circuit developed a fault the other would be in service.

 

[ban-all-sheds]

Because if a DIYer were to get hold of it, without appropriate knowledge, he may miss the "MAX" bit and assume its capacity is 38 amps all the time. Mightn't he?

Might be 47A.