Domestic Kitchen Advice

[rsmck]

We are installing a new kitchen with the following cooking appliances - Combination Microwave rated at 3.2kW, Oven rated at 3.55kW and Hob rated at 7.2kW making a total of around 60A!

The plan was to supply both the oven and hob from a 45A cooker connection unit with a DP isolator protected by a 45A MCB supplied by 6mm T&E from a consumer unit located less than 1m (on the other side of a wall) however then my better half decided to add the combination microwave to the mix.

The kitchen also has a 4mm2 radial circuit supplying the rest of the worktop 13A outlets (and a single dishwasher) and a dedicated socket (on a non-RCD-protected MCB) for the Fridge/Freezer only.

Would you connect the combi oven into the same connection unit and isolator as the other oven (and hob) or just connect the combination microwave into a normal 13A plugtop and outlet ? Alternatively I suppose could run a second 6mm cable from the 45A MCB to a separate isolator for the two ovens (combi+normal oven) and leave the hob on the other isolator - but whilst I can't find anything which would prohibit this it does seem a bit, well, unusual.

Any advice would be greatly appreciated.

[E2A: I know I had a similar thread a while ago, but the kitchen requirements have changed rather a lot (as have many things!) so it seemed more appropriate to start this one]

 

[rsmck]

I'd disagree with you there. If it's a NEF they specifically require a 16A circuit as per manufacturers instructions.

Well it hasn't arrive yet and I haven't read the instructions (as they aren't here!) but the supplier did say it could be connected to a 13A outlet ... that said it *IS* a NEFF so I guess I'll find a spare way for it to get its own 16A circuit...

So in summary, 40A supply (6mm) to oven and hob, 16A supply (2.5mm) to combi / microwave, 32A radial (4mm) for worktop sockets, 10A radial (2.5mm) for Fridge / Freezer == 4 MCBs for a single kitchen in a medium sized 3 bedroom house ... I knew there was a reason I got a 14 way CU...

 

[Voltimax]

Well manufacturers instructions always trump electrical regs provided they are over and above. I know from experience that the NEF microwaves I used to install supplies for specifically required a separate circuit, so if you don't install it their way, then you will void the warranty and have an unhappy customer should anything go wrong. I don't remember what model number the kitchen company i used to sub for supplied however.

 

[Engineer54]

Well manufacturers instructions always trump electrical regs provided they are over and above. I know from experience that the NEF microwaves I used to install supplies for specifically required a separate circuit, so if you don't install it their way, then you will void the warranty and have an unhappy customer should anything go wrong. I don't remember what model number the kitchen company i used to sub for supplied however.

I'd like to see them fight that in a court of law!!! So if every manufacturer stated their kitchen appliance needed a separate 16A supply we would be installing 20 way consumer units in every household!!! These appliances rarely if ever come anywhere near requiring a separate circuit. You design/calculate circuits according to their need not on what a manufacturer arbitrarily states!! ....Total nonsense!!

 

[Voltimax]

Actually Engineer 54 part p states that manufacturers instructions must be followed not me

 

[telectrix]

so with naff, sorry neff, it's "achtung. der mnicrovavegerfunken haben die 16amperdung unt gefinger pokin isxt verboten!"

 

[nickblake]

I wouldnt follow the manufacturers instruction if they didnt comply with the Regs just like the post i put up a few months ago about wrapping tape round terminal block for lights going into the loft

 

[Engineer54]

Actually Engineer 54 part p states that manufacturers instructions must be followed not me

How can a microwave manufacturer stipulate a separate circuit for their appliance?? What are you going to do in a completed kitchen with no means of running another circuit without destroying the kitchen finishes?? Why would you need 16A circuit when fitted with a 13A plug top and probably a 1.5mm cord??


It's the Electrician that makes that assessment and decides if a particular load needs/requires a separate circuit, not an appliance manufacturer!! They can stipulate location, mounting, clearances and other such parameters and the like, for their appliance to run efficiently. They can even make suggestions as to means of supply, or whether it needs RCD protection...but that's about it!!!

 

[malcolmsanford]

I have had this discussion on the PV forum where SMA inverters are to manufacturers instructions installed on a 100mA RCD, not taking into account the UK regs on using 30mA RCD for additional protection.

This IMO is systematic of European Manufacturers not taking in to account, or indeed caring about, UK standards. NEF have UK offices and even if they never. would it be impossible for them to at least write an installation manual that is in line with UK Electrical standards, it is not that hard to adapt one surely.

No they write a generic booklet for everywhere in Europe and this includes the UK, who still have different electrical installation practices to the "other" lot in Europe, and like everything Europe originated, we simply accept this, I bet NEF in America have an installation manual designed to American Standards, because if it didn't then NEF would not sell there.

So instead of UK and the IET doing something to address this, we are slowly going to adopt European wiring standards and all that entails. Regulation 134.1.1 as already started the decline of UK installation methods.

 

[dickllewellyn]

All I can say is the first time I came across one of these microwaves, I thought "that'll be OK, I'll just put a plug on it and plug it in". It wasn't long before the continually blowing fuse suggested that we should have followed the instructions. I've had them knock out 16A breakers in normal operation and had to fit C types to overcome it, hence why a number of them specify a 20A dedicated circuit with a double pole isolating switch with 3mm seperation on the contacts.

*edit.
Including the "Caple" appliances I was connecting just yesterday!

 

[Engineer54]

All I can say is the first time I came across one of these microwaves, I thought "that'll be OK, I'll just put a plug on it and plug it in". It wasn't long before the continually blowing fuse suggested that we should have followed the instructions. I've had them knock out 16A breakers in normal operation and had to fit C types to overcome it, hence why a number of them specify a 20A dedicated circuit with a double pole isolating switch with 3mm seperation on the contacts.

*edit.
Including the "Caple" appliances I was connecting just yesterday!

That HAS to be an industrial Microwave Combo, if it's taking out 16 A MCBs. As i said i have a Sanyo microwave combo, and the connected load stated cannot ever be achieved because you can't combine all the heating elements and microwave generator at the same time.... I don't think i've ever seen a domestic model that doesn't have a manufactures plug top fitted.

 

[Voltimax]

Engineer 54: As I have pointed out part p states manufacturers instructions should be followed not me, so it's no use getting upset with me. You have to remember that anyone carrying out domestic work has to follow BS 7671 and Part P. Let's also not forget that Part P is a statutory document but BS 7671 isn't, believe it or not, it carries more weight.

I don't believe what's written in manufacturers instructions most of the time and I'm more than capable of determining whether something should get it's own circuit or not, but I run a business and I don't want or can afford comebacks, so, if the manufacturer wants a 16A circuit they can have one, so long as they're not asking me to go below the minimum standard I don't care.

 

[Engineer54]

Far from getting upset with you Votimax, Just that far too often these manufacturers instructions, ...if you can actually call them that, are contradictory to to our wiring regulations. And when you calculate the full load that these cooking appliances can ''actually'' provide/draw, makes providing a separate circuit, pretty much wishful thinking!!

As i said earlier, i'd like to see companies like NEFF fight that in a court of law, i'll wager they wouldn't!! As i said before, it's fine if you want to provide a separate circuit in a kitchen refurb or new build, but what about in an existing finished kitchen, where there is no way, to supply that appliance other than say, via an existing ring circuit??

As for the Part Pee thing and the BS7671, agree it makes no sense at all, but then the IET never wanted it to be statutory document. It would mean a lot of tidying up, to make it legally tight enough to stand up in a court of law, even though it has been used as such in certain types of class actions...

 

[Voltimax]

Fair enough and understood Engineer54.
Like you I do feel this industry is getting a little bizarre.