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How do I connect this to the mains

Community Veteran
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Registered: ‎15-06-2007

How do I connect this to the mains

I need to replace my Neff Oven and may well go for the AEG single oven
Simple yes - NO
The Neff happily runs off a 13 amp feed but the AEG is 3.5kW and the specifications calls for it to be fused with a fuse rating - minimum 15 amp maximum 20 amp
Now the feed from the consumer unit is a 30 amp rated fused spur which at present feeds the built in 1000 watt microwave and the oven via individual 13 amp fused DP switches
Thinking laterally
I could replace the 30 amp fuse with a 20 amp fuse then the maximum power would be about 4.8kW which would be adequate for the two units and replace the 13 amp fused switch with a 20 amp DP switch
Would there be any problem with that
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Community Veteran
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Re: How do I connect this to the mains

Legally speaking, consult a qualified, professional electrician before starting any electrical work as these days unless it's wiring a plug (which the H&S bods even have a fit over these days!!) taking on mains electrical work is only legal if completed by a competent individual and signed off by a qualified electrician, also helps with keeping your house insurance valid too...
But yes, what you describe should do the job... Smiley
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Re: How do I connect this to the mains

Regarding legally
It is a bit silly in that I totally rewired the kitchen in my present house before the new regulations came into effect - major extension to the existing ring main - and completely rewired my previous house with a new consumer unit and followed the regulations to the letter (which is more than the "competent" electrician did - 3 double sockets on one spur off the ring main)
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Re: How do I connect this to the mains

Yes, the legal requirements are daft now, there's plenty of competent individuals capable of rewiring a whole house to the letter, but because of the types who aren't competent at even changing a lightbulb having a go, they had to change the law as a "just incase" thing which means that insurance is invalidated if an electrical fault is to blame for fire damage and wasn't completed or signed off by a qualified electrician... Undecided
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Re: How do I connect this to the mains

As there are many "so called"  ( to use a current popular BBC term)... "cowboy builders/plumbers"  ( as seen on t.v.)... who does a "qualified electrician", get his "qualifications"  from ? and , when he "signs off " the work... does he give you an "Official" signing off A4 certificate, ?  do you then have to get that certificate, certified as valid by any "official" body... and  (apart from the fire disaster) how does the insurance company know about it, if you don`t tell them... does the "qualified electrician" also have to inform your insurance company, that he has carried out changes/repairs to the electrical circuitry in the building?
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Re: How do I connect this to the mains

well, electrician qualifications if memory serves me (used to want to be one, but I hate the feeling of electricity coursing through my body as I have experienced many times on supposedly isolated supplies!!) are City & Guilds qualifications, so it's them who issues the qualifications after taking a course on electrical engineering:
http://www.cityandguilds.com
As for signing off and what they give you, dunno to be honest, never had that done myself, but I do know that such documentation has to be seen by your insurer, supplied by yourself I presume, and how do they know about it, well, firemen inspect the building to find the root cause of a fire, and they usually find it and write up a report which somehow goes to the insurers so they know whether to say "you made the mess, so you're boned buddy!" or not... Smiley
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Re: How do I connect this to the mains

To reply to OJ's original question IIRC there is something called diversity. That is all items connected to the circuit will not be drawing full power at the same time, especially when you have control of the units in front of you.
The next question is discrimination, so that the downstream fuses trip indevidually before the backup fuse. For this you need the characteristic curve for each fuse and check they dont overlap. When designing such circuits we used to use HRC fuses for best discrimination.
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Re: How do I connect this to the mains

While understanding the point you are making, in this case it is was more complicated than I first thought.
Originally I was going to leave te 30 amp fuse in the consumer unit and add a 20 amp fused spur
However there doesn't appear to be any such unit available
Regarding diversity - in this case it isn't practical as the oven unit and microwave are often used at the same time on full power - so a 20 amp fuse is needed on the feed to the two units
Note that as presently fitted it has a 30 amp fused spur up the the point where the oven and microwave are connected using individual 13 amp fused spurs (the 30 amp fused spur was needed originally as the original unit was a double oven where you could use both at the same time)
pwatson
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Re: How do I connect this to the mains

I believe a reasonably common solution is to mount a small enclosure with a 20A and 16A MCB fitted nearby and feed the two appliances from the newly split circuit.  The practicality of this depends on the cable run and whether you want the enclosure hidden in a cupboard etc...
Regarding diversity etc, is *all* of the oven on at any one time?  I suspect that the 3.5kW rating is derived from adding up top, bottom, side elements etc and I'd be surprised if you're cooking with all the elements on?
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Re: How do I connect this to the mains

Given that the decision as to what is on at the same time is controlled by the option selector and you can't override it I would have assumed that is was the actual maximum demand.
This could be when doing the pyroclean or the fast heat up option
Note that the oven specification is for a fuse of not less than 16 amp and not more than 20 amp and it is rated at 3.5kW
Regarding the small enclosure - that would certainly be a viable option - will need to check
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Re: How do I connect this to the mains

Jim, where does your hob get power, I only ask because it's usual for that to be fed off the same cooker spur as the oven and it's not been mentioned?
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Community Veteran
Posts: 38,460
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Registered: ‎15-06-2007

Re: How do I connect this to the mains

from the ring main   -   it is gas so only the automatic igniter - and nowhere near the oven  Grin
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Re: How do I connect this to the mains

Further checking and to my untutored eye - I haven't used one of these before
This enclosure http://www.screwfix.com/p/wylex-ip40-insulated-enclosure/32311 with one of these http://www.screwfix.com/p/wylex-16a-sp-type-b-mcb-6ka/88460 would do the job
 
pwatson
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Re: How do I connect this to the mains

Yes - That's what you need.  Depending on how the cable to the microwave is routed, you may find it easier to pull back the (6mm?) feed, fit an additional breaker in the enclosure and run a smaller cable to the microwave?
The MCB is single pole of course, so you'll also need something to join the neutral and earth cores. 
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Re: How do I connect this to the mains

At present there is a full 30 DP isolator for the oven and microwave feeding two 13 amp fused spurs and all I need to do is change the oven spur to a DP switch and add the mcb
Actually adding another DP switch possibly isn't essential but would probably be a good idea