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Ovens and 30A fuse/feed

Hello, I googled and found some info in the old IET forums, which has generated this post.

We need to replace our double oven. For the last 20 years, a 30A trip fuse has provided power to a dual wall socket (kettle 2.2kw, microwave 1.29kw) and the oven with a 5.1kw max rated power consumption. I've discovered this by tripping the 30A fuses in the fuse box to see which appliances were still live. 

It appears that when the kitchen was fitted (20 years ago), the original standalone cooker on/off master switch was converted to a dual wall socket and the then a spur used for the double oven.

According to my maths this is a total of 35.79A @ 240v which is more than 30A, although I'm guessing the times all three appliances have been on at the same time would be infrequent.

ApplianceLoad rating (kw)Amps (at 240v)
Current oven5.121.25
Kettle2.29.166666667
Microwave1.295.375
total8.5935.79166667

Why has the 30A RCD at the fusebox not tripped when they have been on at the same time?

The new oven has a load rating of 6.2kw. This increases the total amps to just over 40A. 

ApplianceLoad rating (kw)Amps (at 240v)
New oven6.225.83333333
Kettle2.29.166666667
Microwave1.295.375
total9.6940.375

I'm guessing this may cause some issues with the 30A feed. Would a more modern 32A be better?

I suppose I could always move the kettle and microwave to other sockets in the kitchen which are on a different 30A circuit.

Please could I have your comments? 

Thank you

Paul

 

 

Parents
  • The installers will install the oven to a correctly installed circuit.

    So they will install to a circuit with an accessible local isolation switch and a cooker connection unit behind the oven.

    If the switch has a single socket on it then convention is that the load is assumed to be 5-amps when calculating load diversity for a cooker. But you cannot really allow diversity for a single oven, only a double oven or a full blown cooker.

    If the oven installation instructions say the oven needs to protected by a 16 or 20 amp circuit protective device then again the installers may walk out without doing the job.

    If the cooker circuit has basically been converted to a socket radial circuit then the installers may refuse to just wire the oven to it.

Reply
  • The installers will install the oven to a correctly installed circuit.

    So they will install to a circuit with an accessible local isolation switch and a cooker connection unit behind the oven.

    If the switch has a single socket on it then convention is that the load is assumed to be 5-amps when calculating load diversity for a cooker. But you cannot really allow diversity for a single oven, only a double oven or a full blown cooker.

    If the oven installation instructions say the oven needs to protected by a 16 or 20 amp circuit protective device then again the installers may walk out without doing the job.

    If the cooker circuit has basically been converted to a socket radial circuit then the installers may refuse to just wire the oven to it.

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