3.6Kw Microwave

[opps]

Hi all

My microwave combi oven kicked the bucket. I purchased a new one.

It had the same rating as the old one (3.6Kw).

In the original set up, a 6mm cable runs in to a 50amp junction box, from there two 2.5mm T&Es run to two 13 amp fused spurs (single oven and microwave).

The instructions for the new microwave say that a 13amp fused spur must not be used.

I guess that I need a 16amp fused spur- do they exist though?

 

[Taylortwocities]

I guess that I need a 16amp fused spur- do they exist though?

No, a 16A fused spur does not exist. The maximum fused device that can be connected to a ring final is 13A. You may have got away with it with the old M/W.

To do it properly, you would need to connect to the 50A junction box, not to the fused connection unit.

two questions.
What is the value of the FUSE/MCB on that 6mm circuit?
Does the manufacturer specify a protective fuse value for the microwave?

 

[ericmark]

After 13A we jump to something like this

the fuse carrier jumps in size

so needs a massive box so normally it's mounted in the main consumer unit and an isolator

and a cooker connection unit

are used instead. Only in the UK is the ring final system used rest of Europe uses radial circuits so once you leave goods designed for UK than you have to use the European system sorry.

 

[opps]

Hi guys, thanks for the replies.

I went to my local supplier looking for a two way consumer unit (with a blank and a 16 amp breaker) but they only had 4 way ones. In the end I ran the 6mm into a cooker switch, had the neutral load running to the microwave and then ran the 6mm live from the switch into the 16amp breaker in a small plastic box, with the live load running off that.

The cooker switch gives me dual pole switching and the breaker the required protection.

After doing it I went to the pub, started talking to an electrician who said that the 13amp switched fused spur would have been allowed under diversity. His regs say that after the first 10 amps you allow for 30% diversity, resulting in just under 13 amps.

 

[ericmark]

Diversity is only allowed when all of the items are unlikely to be used together. So for a hob with 4 rings it's unlikely that all four rings will be switching on at the same time each ring will be switching on and off to regulate temperature.

Your oven however is one item so no diversity.

It it was a twin oven then there would be diversity but you have not indicated it was a twin oven.

 

[JohnW2]

Diversity is only allowed when all of the items are unlikely to be used together. So for a hob with 4 rings it's unlikely that all four rings will be switching on at the same time each ring will be switching on and off to regulate temperature. Your oven however is one item so no diversity.

I'm not at all sure about that - there is 'diversity over time' as well as 'diversity over place' - i.e. even with a single-element oven, the thermostatic control means that the average current over a 'reasonable period of time' is appreciably less than the 'maximum' (i.e. when 'on') current.

The guidance in the OSG regarding diversity does not make any distinction. It allows the standard diversity formula ("10A + 30%") to be applied to any domestic cooking appliance, without excluding single ovens.

Kind Regards, John