cables in loft with extra insulation

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I have put extra loft insualtion in my loft, now a total of 300mm.
At the sam time I have installed additional beams at 90 degreees to existing joists supportin flooring for storage.

There are 2.5mm cables for ring circuits on 32 amp mcb, 1.5 mm lighting circuits on 6 amp mcb and 10mm cooker circuit on 45amp mcb. 2.5mm immersion on 20 amp mcb.

Currently I have run the cable loose accross the insulation with the cooker and ring main cable passing vertically through the insulation. The lighting may have up to 30cm of cable under the insulation, pinned to joist or in contact with plaster board.

Based on other posts and advice from others I am confused as to weather it would be best to clip the cables against my new beams, which would be just above or close to the top of the insulation. Is there anything else I need to consider?

Any advice will be appreciated
 
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It doesn't matter about the lighting circuits as the MCB rating is much less than half of the cables' current carrying capacity.

However, you will have to separate the 2.5mm² and 10mm² cables from the insulation as traveling through it (for 300mm) and being enclosed by it will result in derating the CCC to below the MCB rating and therefore is not acceptable.
 
I have put extra loft insualtion in my loft, now a total of 300mm.

There are 2.5mm cables for ring circuits on 32 amp mcb and 10mm cooker circuit on 45amp mcb. 2.5mm immersion on 20 amp mcb.

Currently I have run the cable loose accross the insulation with the cooker and ring main cable passing vertically through the insulation.
Your lighting circuit will be okay as even 50% de-rating will only reduce the safe current capacity of 1.5mm t&e to 10A so okay on a 6A device.
What distances are the vertical lengths of the cable for power circuit passing through the insulation, is there any that run horizontally through it?
It is advisable to avoid routing cable through insulation unless the circuit has been designed to do that.
Based on other posts and advice from others I am confused as to weather it would be best to clip the cables against my new beams, which would be just above or close to the top of the insulation.
It would be best if you could clip cable above insulation levels.
Is there anything else I need to consider?
If you are boarding/panelling loft floor, avoid covering any junction boxes of joints made in the cables, as these are likely to be needed to be left accessible or install traps to access them.
Also if cables are run through joists where you are laying loft floors, make sure they will be free from mechanical damage from nails/screws, leave at least 50mm distance between top and bottom of joist.
//www.diynot.com/wiki/electrics:installation_techniques:route
 
What distances are the vertical lengths of the cable for power circuit passing through the insulation,
300mm, I reckon:
I have put extra loft insualtion in my loft, now a total of 300mm.

Alan - the current carrying capacity of the 2.5mm² will be reduced to about 15A, and the 10mm² to about 35A. You need either larger cables or an insulation-free route for them.
 
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Thanks for teh advice. As they are passing through the insulation to allow them to drop in to an internal wall it sounds like my best solution is to use some 32 mm drain pipe to keep the insulation away from them.

Will it be ok to just check the top of the plastic pipe is free of burrs or is there a god trick to create some sort of cable protection at the pipe entry? Mabe a few layers of caroet er gaffa tape?
 
There will still be a de-rating for running through conduit and a de-rating for running through conduit within thermal insulation. Ref Method A, would suggest:
1.5mm=14.5A
2.5mm=20A
10mm= 44A
 

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