Loft insulation away from electrical cables

[snrweb]

Hi, i am installing some loft insulation on top of the old vermiculite in between the rafters up in the loft.

I know the instructions tell me to move electrical cable above the new insulation but this is not really possible as

a. many cables are clipped to the sites of the rafters (other than where they go to a ceiling rose)

b. there is not enough slack in the cables above to move them.

How important is it to do this? There are no downlighters in the upstairs rooms, just simple ceiling light fittings with the bulbs well in the room space.

The single juction box in the loft is on the top of a rafter and well clear of any loft insulation.

The cables are for lights only and so surely these cannot get hot to a dangerous extent?

Most grateful for any advice.

 

[Chri5]

Have you changed the bulbs for energy saving ones ?

If so the total load of the lighting circuit (add up all light watts value) you intend to cover in 100/150/200mm (?? what size) insulation is ???

Light are mostly ok if es type, but cable size and age may come in to play.


Shower cable is the big risk, since the load always tends to be very close to the cable capacity in open air.

 

[snrweb]

Have you changed the bulbs for energy saving ones ?

If so the total load of the lighting circuit (add up all light watts value) you intend to cover in 100/150/200mm (?? what size) insulation is ???

Light are mostly ok if es type, but cable size and age may come in to play.


Shower cable is the big risk, since the load always tends to be very close to the cable capacity in open air.

Thanks for the reply. I think the total load is 300W and not energy saving.

It is the white (red/black) cable from the 90s and lighting only


The insulation depth will be 300-325mm

 

[flameport]

If the circuit has a 6A MCB, then it won't matter what insulation is placed over the cables, since even with the maximum derating, the cable is still suitable for carrying more than 6 amps.

 

[Chri5]

If the circuit has a 6A MCB, then it won't matter what insulation is placed over the cables, since even with the maximum derating, the cable is still suitable for carrying more than 6 amps.

Can you point me in the direction of a derating factor for 325mm of insulation ?

The ref method table seem to be fixed to 100mm only.

 

[holmslaw]

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