topic Re: How do I connect this to the mains in Tech Help - Software/Hardware etc

How do I connect this to the mains

Oldjim — Thu, 02 Apr 2015 16:29:41 GMT

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

Re: How do I connect this to the mains

twocvbloke — Thu, 02 Apr 2015 17:20:35 GMT

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...

Re: How do I connect this to the mains

Oldjim — Thu, 02 Apr 2015 17:39:40 GMT

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)

Re: How do I connect this to the mains

twocvbloke — Thu, 02 Apr 2015 17:56:47 GMT

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...

Re: How do I connect this to the mains

shutter — Thu, 02 Apr 2015 20:00:08 GMT

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?

Re: How do I connect this to the mains

twocvbloke — Thu, 02 Apr 2015 22:10:03 GMT

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...

Re: How do I connect this to the mains

PeterLoftus — Fri, 03 Apr 2015 06:59:58 GMT

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.

Re: How do I connect this to the mains

Oldjim — Fri, 03 Apr 2015 10:00:19 GMT

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)

Re: How do I connect this to the mains

pwatson — Fri, 03 Apr 2015 10:26:43 GMT

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?

Re: How do I connect this to the mains

Oldjim — Fri, 03 Apr 2015 10:36:33 GMT

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

Re: How do I connect this to the mains

w23 — Fri, 03 Apr 2015 11:02:05 GMT

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?

Re: How do I connect this to the mains

Oldjim — Fri, 03 Apr 2015 11:05:01 GMT

from the ring main - it is gas so only the automatic igniter - and nowhere near the oven

Re: How do I connect this to the mains

Oldjim — Tue, 07 Apr 2015 14:44:00 GMT

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

Re: How do I connect this to the mains

pwatson — Tue, 07 Apr 2015 14:51:29 GMT

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.

Re: How do I connect this to the mains

Oldjim — Tue, 07 Apr 2015 14:56:13 GMT

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

Re: How do I connect this to the mains

Oldjim — Fri, 10 Apr 2015 13:42:28 GMT

Slight hiccough
Decided on the unit we wanted but as a final check looked at the installation diagram
Who would have thought it - the unit depth is deeper than normal by about 2" so it won't fit in my 560 deep unit - needs a 600 deep unit
Just goes to show - assuming that modern oven units would use the same cabinets was a mistake and could have been a very expensive one

Re: How do I connect this to the mains

pwatson — Fri, 10 Apr 2015 13:45:06 GMT

Out with the chisel then
Best of luck with hunting for the right oven - You never know it might be less than 3kW

Re: How do I connect this to the mains

Oldjim — Fri, 10 Apr 2015 13:49:56 GMT

It will be either a Neff or a Bosch but checking with a Neff dealer the one I was considering is being replaced with a new model this month
Not yet on the UK website but is on the Belgium one and doesn't look too bad so another slight delay - fortunately the present Neff unit is still working albeit with a rather noisy fan and no internal lights
Note that replacement cost for a Neff fan/motor unit plus lights including fitting is topside of £200 and probably nearer £250 which is why I am going for a new one

Re: How do I connect this to the mains

twocvbloke — Fri, 10 Apr 2015 15:59:56 GMT

That's one of the things I hate about manufacturers today, build something for pennies, sell for top dollar, and charge extorionate prices for replacement parts making it uneconomical to maintain and repair...
It's why I like old hardware, easy to fix, plentiful affordable spares, and keeps things out of the dump...

Re: How do I connect this to the mains

PeterLoftus — Fri, 10 Apr 2015 19:49:10 GMT

Quote from: twocvbloke

It's why I like old hardware, easy to fix, plentiful affordable spares, and keeps things out of the dump...

Try telling that to SWMBO new kitchen is required so perfectly good eye level oven, dishwasher and fridge all fitted are all due to be trashed