Enough with the electrical questions ! What are the main uses of 4mm TWE, since it has a disproportionately small CPC ? If I decide to have a single kitchen ring with sockets and fixed appliances off it, any use running it in 4mm instead of 2.5mm ? Cheers, Simon.
The main use would be a 32A radial - either for general power circuits, or for fixed appliances like cookers.
Only if your cable will be subject to de-rating factors that will make the 2.5mm^2 inadequate. Given the choice, stick to the smaller cable - its far easier to work in confined spaces.
Good point about workability. I have 6mm down for my 32A radials (fixed appliances, oven/hub, outside sockets/shed). Thats probably a good idea for outside and oven, but not sure about the fixed appliances. I could do that in 4mm. Simon.
Kitchens...
32A Rings are done in 2.5mm FTE. 32A Radials are done in 4.0mm FTE (some kitchens are anti-ring re space).Each room...
20A Radials are done in 2.5mm FTE.If for derating reasons you need to go up a size, you can instead use
6242BH instead of 6242YH. The B means XLPE insulation which has a 90oC temperature limit in place of PVC's 70oC figure. For example 6242BH 1.5mm is used for lighting in some very large super insulated houses for this reason. It does NOT mean you can use the 90oC current figure at the wiring accessories (most are limited to 70oC), instead you use the 90oC higher current figure for grouping (*1) & insulation calculations (you have a higher starting point with which to end up at not less than 20A per ring leg or 6A for lighting).Originally our kitchen had a 6mm radial, and a pig to work with. The kitchen fitters extended it in 2.5mm to three double sockets carrying all the heavy appliances. Needless to say the PVC cable was stuffed. I broke Part P by using 4.0mm 6242BH - technically you should use the exact same cable size.
I just put a comment to that effect on the other thread. Indeed, you will have difficulty doing a socket circuit in 6mm^2. Its also overkill unless you have some pretty severe derating factors to take into account.
In a recent kitchen I did, with a new triple section CU
On RCD's section of CU:
2 32A radials in 6mm to an induction hob and double oven. 1 32A ring in 2.5mm 'above' counter for the usual kettle, toaster, microwave type applicances.On the non RCD'd section of the CU but with individual RCBO's:
1 32A ring in 2.5mm 'below' counter for DW, WM, FF & wine cooler. 1 6A for the lighting.Tim.
Yep. It it perhaps a choice between a 32A radial in 4mm of 32A ring in
2.5mm for the below counter. Simon.
One advantage of the 4mm radial is that you do not have to balance the load.
I would say a 4mm radial for the DW and WM would be ideal.
In the mentioned kitchen, the DW & WM turned out to be at opposite ends of the kitchen, and the 1st fix had to be done several weeks before the final kitchen design had materialised, so had to be as flexible as possible! :(
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