Which Reference method

[Blacktail]

Thanks Edd, I can feel the confidence seeping away by the minute!! Using the worst case approach it would be method 102 poss 103. 102 if laying it as Guitarist suggest which is starting to sound like the best idea. As far as i can see the OSG does not even list ring cicuits in 103 in its Final Circuits so im guessing they really dont like the idea and I dont fancy 6mm t+e in shallow backboxes.

If laying on top of insulation, 25 mm pvc conduit sufficient for mechanical protection. Really appreciate your input guys.

 

[Guitarist]

Just as a side (and I realise many don't agree with this), it's worth testing your cabling before the floor is actually laid. Just link your cables in choccy block and carry out cont and IR tests at the ends. This way, you know that nothing has been nipped and that the cabling is good to begin with.

 

[topquark]

Dumb question time, is the oak boarding to be floating or fixed? If it's floating then you could run the conduit within the ply layer (not if fixed though).

I don't think LABC will be happy with you channeling out the underfloor insulation TBH, unless it's been over specified (depth wise).

 

[sjm]

Reference method 100 to 103 are used for T+E with at least 1 side of cable in contact with insulation material. Therefore if the cables are in conduit they are not in contact with the insulation material so reference method A will apply to the cables. Use table 4D5 column 7 of appendix 4 for CCC of cable.

IMO I would fix my cables in conduit on top of the concrete pad under the insulation. Perhaps you could install a few radial circuits for sockets, instead of a ring, to cover the lower CCC of cable in insulation.

 

[Guitarist]

If you are going under the insulation, even in conduit, then agree method A, so radials may be a better solution. I can't really see an inch notch of insulation really affecting the insulation rating of the building tbh, but BC can be funny at times over negligible things. Maybe best to ring them up and ask what they would be happy to see.

 

[topquark]

I've had it once before Guitarist. They don't like the reflective foil being breached. If it's not spec'ed with aluminium foil for the joints then they prob won't be too worried, as you say though best to ask.

 

[Blacktail]

Sorry seem to be having problems posting and you have all got ahead of me!! , but reassuringly you seem to have come to same conclusion that ref method A is the way to go. And radials look like a better option. The insulation is over 100mm and so dont think there should be a problem but take on board what you are saying. Inspector is on site this pm so will get builder to ask.

Guitarist, sjm, topquark thanks for the input didn't think i would fall quite so heavily at the first fence in my design, hopefully not bother you all again!!

 

[pmcsparks]

Managed to get conduit laid in/under the concrete sub-floor at the last conservatory I did.
So method B60 worked for me. Ran two radials for sockets, tails run up in conduit to back-boxes.
Lighting was all in ceiling, clipped to joists and surrounded by insulation, so method 101 there.