Derating cables laid on top of loft insulation

[briefcasedan]

Hi All, opinions please, just been to a property that has a 6mm cable ontop of 200mm of loft insulation so not buried. What de-rating factor would everyone apply to this
Would it help if i could get it in some big trunking?

 

[James]

Clipped direct?

 

[briefcasedan]

Clipped direct?

No the cable is just laid loose on insulation.
Dont think there is enough slack to clip it to joists

 

[James]

I would not be de rating cable being on top of insulation, but it should be adequately secured along its length.
If this is a loft, you might need to de rate for ambient temperature.

 

[Vortigern]

I imagine it must pass through the insulation at some point so 0.68 off the top of my head.

 

[Julie.]

I would not be de rating cable being on top of insulation, but it should be adequately secured along its length.
If this is a loft, you might need to de rate for ambient temperature.

I imagine it must pass through the insulation at some point so 0.68 off the top of my head.

These

Clipped direct, with adjustment for ambient, or through insulation (depends on thickness @ that point(s) ) or whatever the rest of the run is whichever is the largest de rating

 

[Dustydazzler]

Laid on top then I personally would not apply any correction factor

laid underneath for most of the run then its about 0.6 or something

 

[Ian1981]

Laid underneath would depend on the amount of insulation ie T&E above a plasterboard ceiling covered by thermal insulation not exceeding 100mm would be reference method 100, exceeding 100 mm would be 101, from there you would look at the appropriate table in appendix 4 for the ccc of the cable.
You may need to apply further correction factors where applicable.

 

[briefcasedan]

Laid underneath would depend on the amount of insulation ie T&E above a plasterboard ceiling covered by thermal insulation not exceeding 100mm would be reference method 100, exceeding 100 mm would be 101, from there you would look at the appropriate table in appendix 4 for the ccc of the cable.
You may need to apply further correction factors where applicable.

Thanks all for your thoughts.
As i said cable is on top of insulation and not underneath.
Very hard to clip to anything as there is no slack to move cable so basically just sits on top.
Wonder if there is any merit in placing in some big trunking, 50mm x 50mm, but again what reference method would this be classed as?

 

[Ian1981]

Thanks all for your thoughts.
As i said cable is on top of insulation and not underneath.
Very hard to clip to anything as there is no slack to move cable so basically just sits on top.
Wonder if there is any merit in placing in some big trunking, 50mm x 50mm, but again what reference method would this be classed as?

Just leave it clipped above, installing it in trunking would be reference method B and will reduce the ccc , further to any other factors.

 

[Vortigern]

The question is does it penetrate the insulation and thus become totally enclosed by insulation. If less than 0.5m then derating will have to be applied. Unless it goes past the insulation and down to (say) the shower.

 

[Dustydazzler]

Trunking in the loft not necessary

 

[Baddegg]

Sounds to me like it’s a problem for the donut who decides they needs another 100mm of insulation on top....be unusual if it doesn’t pass through the existing insulation at least somewhere though......