Which cable?

[cdbe]

I'm doing my first fix for our future kitchen. I think it'll be single oven and induction hob, possibly a second oven, one of those steam things.

At the same time I'm reflooring the ground floor, incorporating underfloor insulation - there will be no access under the majority of the floor in the future (continuous glued down lvt and with the insulation the void will be too small anyway) so I'm trying to lay in all the cables at this stage (they'll be clipped below the insulation).

I'm trying to use up my collection of cable so I'm wondering if any would be suitable?

Basically I have enough 10mm to run two lengths from board to kitchen (about 7-8m) - obviously massive overkill, or enough 6mm for one run, and/or the existing 6mm which isn't long enough (but could be joined and accessable from the one place I'll still be able to get under the floor).

So I think the options are two separate 10mm circuits, a 10 and a 6, a single 10 split at the kitchen, two 6mm (one new and existing extended) or some of the combination or none of the above!

At the board is the existing oven and next to it a spare from an old shower.

Obviously I'm trying not to buy new stuff if I can use what I already have.

Just had another thought, would it be worth running another cable from board to front of house for a future EV charger while I have access? Plenty of 10mm available!

Thanks.

Collection of cable:

Board:

 

[Murdochcat]

Belt and braces is 2 seperate radials to the kitchen then you’ll have your options covered.

They both will need to rcd protected and tested correctly and fall under Part P

 

[ericmark]

I have in the past fitted spare cable just in case, using 3 and earth for switch drops yes used extra core for 2 way or neutral, but rest never used.

 

[EFLImpudence]

They both will need to rcd protected and tested correctly and fall under Part P

All electrical works in dwellings 'fall under Part P'.

 

[Murdochcat]

All electrical works in dwellings 'fall under Part P'.

Ha ha ha

No they don’t

 

[EFLImpudence]

Yes they do.

 

[cdbe]

So 2x 6mm radials I think, plus some 10mm (or maybe just a piece of rope) to provide for a future car charger, replace the two unprotected rcd's with rcbo's to suit the appliances. I presume 6mm will be ok for an average sized induction hob? I know when Wren kitchens did my brother-in-law's he could only use two rings at a time.
My nephew and his "associate" will sort the testing and paperwork.

 

[RandomGrinch]

Ha ha ha

No they don’t

It does seem to cover a pretty broad sweep...

 

[ericmark]

The problem is how does one test and document a cable not connected to anything? The installation certificate can have three signatures, however to use that option precludes in most cases self certifying as a scheme member, but some one has to sign for design, installation, and inspection and testing. With no power you can't really test.

So some one in the future is presented with a cable where he has no idea of the route, or any branches along its length, often with no paperwork, and to be frank the standard installation certificate is some what lacking, it often does not say how many points it serves, or what route taken, and we really only know likely route bases on the MCB/RCBO size at the consumer unit.

I know I have down graded a radial when I found some one had clearly thought it was a ring final, and had extended it with 2.5 mm² instead of the 4 mm² the rest of the radial used, so swapped the 32 amp to a 20 amp MCB. How an electrician made the mistake I do not know, as one should test it is a ring. And not DIY as always there was an electrician on site.

So putting in a pipe to pull cables through in the future OK, but putting in the cables, only if terminated into a cooker connection unit or the like. And then it can have the paperwork raised and have all test results.

As to Part P yes it covers all domestic installations after the DNO equipment, but only some items need notifying, however this does not preclude to raising of an installation or minor works certificate. OK some times we are lazy and don't test, and in the main we get away with it, however if you look at cases where it has gone wrong, it is often not just one error, the Emma Shaw case there was an electrician, electricians mate, plaster, plumber, and the electrical Forman who all made errors.

We rely on the paperwork in such cases as a get out of jail free card, yes one can fudge the results, and that fudge was found out with the Emma Shaw case, lucky cases like that are rare, but often it is years latter when it all comes to light, we should get an EICR done every 10 years, 5 years with rental, and so one would hope after 10 years, your clear, unless your the guy who should have commissioned the EICR and did not.

In Wales the kitchen is still a special location so one needs to notify all work anyway. Personally I would use all RCBO's, but that is my personal preference. The RCD's will need renewing if any new circuits installed, they are type AC we now use type A, they are also only 80 amp, it depends on the DNO fuse as to if that is OK or not.

When it all goes wrong is when some one drills through a cable or similar and the HSE is called in, other than that who will know? But it is a big chance to take.

 

[EFLImpudence]

So 2x 6mm radials I think,

Why are you asking these questions?

ONE 32A 6mm² radial (installation method allowing) is adequate for any domestic cooking appliances you are likely to install.

That you want to install two or use even larger cable because you have it is irrelevant.

plus some 10mm (or maybe just a piece of rope) to provide for a future car charger, replace the two unprotected rcd's with rcbo's to suit the appliances.

Ok.

I presume 6mm will be ok for an average sized induction hob?

Yes it is oversized (installation method allowing); 4mm² would be sufficient.

I know when Wren kitchens did my brother-in-law's he could only use two rings at a time.
My nephew and his "associate" will sort the testing and paperwork.

That will not be related to the cable size.

 

[cdbe]

Thanks, so 6mm is adequate, the relevance of 10mm is that I have it and it would avoid extending the existing 6mm radial if I could use a continuous length of 10mm. 4mm vs 6mm - fine but I don't have any 4mm. I'm not an electrician so I can't just chuck it back on the van etc - I either use what I have or it goes on my scrap pile and I "waste" £40 on a roll of 4mm.

I don't know the details about the two ring hob, I think it was connected to the ring where the old gas ignitor had been plugged in, but it worked fine after electrician ran new cable in.

I've already been made aware of the need for new RCD's, but the ones I have are still only 80amp, main fuse is 100amp??

 

[EFLImpudence]

Thanks, so 6mm is adequate, the relevance of 10mm is that I have it and it would avoid extending the existing 6mm radial if I could use a continuous length of 10mm.

Yes, I know. Obviously you can use cable that is larger than required, but it is a waste.
You could use a continuous length of 6mm² - or 4mm² (if installation method allows).

4mm vs 6mm - fine but I don't have any 4mm.

Then buy some or use your 6mm².

I'm not an electrician so I can't just chuck it back on the van etc - I either use what I have or it goes on my scrap pile and I "waste" £40 on a roll of 4mm.

Ok.

I don't know the details about the two ring hob, I think it was connected to the ring where the old gas ignitor had been plugged in, but it worked fine after electrician ran new cable in.

Yes, but because he installed a proper circuit.

I've already been made aware of the need for new RCD's, but the ones I have are still only 80amp, main fuse is 100amp??

Why? There are two of them which is 160A.

 

[EFLImpudence]

Just seen your picture.

A different type of RCD; not because they are 80A.

Better do it quick before they change the rules again and you need something else.

 

[cdbe]

Thanks,

the 80amp? was with reference to Eric:

, they are type AC we now use type A, they are also only 80 amp, it depends on the DNO fuse as to if that is OK or not.

 

[ericmark]

A consumer unit can go up to 125 amp single phase, but only seen rated at 100 amp, the DNO fuse can be 60, 80 or 100 amp, if total of all MCB's under or equal to size of RCD protecting them it is OK, or the RCD is over or equal to DNO fuse OK.

However since a plastic CU, it would seem prudent to change it and go to all RCBO with SPD so really it does not matter.