Is this "surrounded by insulation or on 100mm insulation in your opinion?

[Vortigern]

Just designing and taking into account the factors for insulation and can't decide on surrounded or on top of 100mm. What say you? Cables will be in metal banding inbetween the two layers as in pic. So to be clear it will be under the upper board in pic and above the lower board on top of the lower rockwool (accoustic)

 

[Vortigern]

I had not thought of that. A really good thought. Thanks @Pretty Mouth That gets me up to 26a.

 

[pc1966]

You've probably considered this already, but where the cables run through the insulation, running them in flexible conduit brings you to ref A. This will allow most of the standard circuits in standard sizes, eg 32A/6mm cooker, 32A/2.5mm ring etc.

Trouble is you would have to run each T&E in its own conduit or you are penalised by the grouping factor.

I'm not sure the effort of puting in conduit is going to make up for any savings in copper cost or termination effort in going 4mm!

Surprised that a 4mm ring can be run ref 103. They are very flexible circuits those rings.

Indeed, a very good solution for a typical flat/floor.

 

[loz2754]

There is a very informative efixx video that explains the balancing of loads on a ring circuit.

 

[Vortigern]

Thinking about it if I got out of the ceiling and went horizontal along the walls I would be Ref:102 which would assist me and get me up to 27a rating with 4mm.

 

[pc1966]

Thinking about it if I got out of the ceiling and went horizontal along the walls I would be Ref:102 which would assist me and get me up to 27a rating with 4mm.

If you can do that it would be the easiest/cheapest option.

 

[Vortigern]

Curious to know why you call spurs "the devils work" @pc1966. Is it because they like melting down when loaded with immersion elements and the like?

 

[pc1966]

Curious to know why you call spurs "the devils work" @pc1966. Is it because they like melting down when loaded with immersion elements and the like?

Two reasons really,:

• If you see 3 cables at a socket, you don't know for sure that the spur is just one socket (as it should be) or has been extended.
• It breaks the assumption that your end-end r1,r2,rN measurements are testing every socket on the RFC. If there is a spur, it has to be found and tested separately.

If you have a radial that is "pure" (i.e. end to end links, not a tree branching off in various directions) then you might know the end socket and can do similar CU-end tests to check that R1 = RN and R2 is in known ratio to R1 (for T&E) but you don't get as sensitive a test of socket/contact resistance as the figure-of-eight where in the RFC all should be identical.

 

[aankhka]

I'm seeing 32A radials as OK for 10mm in the OSG for method 103 so if they can all be run with a good spacing apart then cooker & 6kW heater are fine that way. Not sure if anywhere has a definition of how far apart is "good" but my own gut feeling is at least the 10cm or so of the insulation thickness.

 

[Vortigern]

Hi @aankhka as you can see above I can go 102 by horizontal wall installation and use 4mm. I don't think cost and practical wise 10mm is going to work on sockets especially two 10mm!

 

[brianmoooore]

There are thousands upon thousands of bungalows in the UK, where all the wiring was in the loft, sitting above the 4" or 6" insulation fitted. Much of this has since been covered up with at least another 6" of insulation, fitted under some free government scheme or other, leaving all the power cables nicely totally enclosed in thick insulation.