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Hi, been looking at which reference method would be suitable in this case. The cable drops of a ring circuit to each socket are fixed direct to a concrete block wall (using capping) ; kingspan boards are to be dot&dabbed directly to the wall. Im thinking worst case would be ref method 102; however as any heat will be dissipated through the concrete wall its fixed to, would I get away with ref method C in this case ?
 
I would think that would be reference method A, the cable is not against the room side but should be able to dissipate heat to the concrete wall but will be constrained on the kingspan side.
 
I'm thinking it would be method 101, albeit its specific to ceilings, its for flat twin & earth cables covered by insulation with U value of minimum of 0.1.

What are the cables, what Kinspan insulation is it?
 
Its 2.5 t&e already been wired, the kingspan is expected to be 100mm or 50mm.
Method 101 is not really the same situation as it relys on cable clipped to a wooden joist or touching plasterboard ceiling, not a concrete wall which would dissipate heat better. Method 102 is virtually the same definition as 101 except that 102 its in a wall (vertical), not a ceiling (horizontal); are the ccc differences of 101 & 102 due to heat rising and dissipation. Then theres always ref method B, which in this situation is similar, but not exactly. Basically I dont want to downgrade ring to 20A !
 
I’d Consider going for 102 which is fine for your 2.5mm ring.
Tho it states for a stud wall with the cable touching the inner wall surface.
 
I’d Consider going for 102 which is fine for your 2.5mm ring.
Tho it states for a stud wall with the cable touching the inner wall surface.

My reasoning after some research suggests dense brick dissipates heat at a higher rate than plasterboard; with that in mind the ccc should not be any lower than for that of ref method 102 ! Unless im missing something
 
There is somewhere that table that quantifies de-rating factors for cables buried in thermal insulation, that de-rates the ccc by up to a half, if its covered fro more than 500mm. Can't find it in BS7671 at the mo?
 
Just look in the index listing the various tables at the back and you’ll find it.
Or look up thermal insulation and the table is next to the regulation regarding cables in thermal insulation
 
Just look in the index listing the various tables at the back and you’ll find it.
Or look up thermal insulation and the table is next to the regulation regarding cables in thermal insulation

Thanks, I have the same trouble finding my keys in the morning.
 
Ok that was a bad suggestion.

Looking at reference method A, that would be for multicore cable in a thermally insulated wall.......having a thermal inductance of not less than 10 W/m2K, Kingspan (I think) would give a lower figure than that.

But if we did use A, 2.5 sheathed flat ccc is 20a, whereas 102 is higher at 21a. So I'm not convinced 102 is the appropriate method, if you see my reasoning.
 
It could be argued that applying ref method A to t&e does not consider the extra surface area, spacing of cores, and absence of insulation in the earth (which may act as a heat sink); with that in mind it could bring it more on par with 102.
However, in this case as long as the rating is 20A then thats all I care about today; so will be applying ref method A. Thanks all
 

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