PV cables through cellulose?

[Stratman]

Hi there!

 

Getting ready for roofing and in roof PV panels on our MBC build. PV installer says he'll run cables from the PV panels through laps in the roof felt, through the 400mm blown cellulose void between rafters (going in after) then through the vapour barrier below the rafters.

 

Do you have any thoughts about this as I am a bit worried about cables overheating and causing a fire. Is this an accepted approach to cabling?

[SimonD]

I'm not an electrician but my electrician was always reluctant to run cable through insulation like that. Instead all cabling was run in ducting installed through the insulation so there's at least some air gap between the cable and duct.

[Onoff]

Have a look here at 4.3.6. Gives the gist.

 

https://www.tlc-direct.co.uk/Book/4.3.6.htm

[Dillsue]

13 hours ago, Stratman said:

Do you have any thoughts about this as I am a bit worried about cables overheating and causing a fire. Is this an accepted approach to cabling?

How is any other cabling being routed in and around the insulation??

[Stratman]

Thanks - the TLC guide explains the issue well and how to overcome it. Discussed with installer and he has already compensated for the derating by increasing cable sizes from the panels to a rotary isolator in the loft space.

[MikeSharp01]

10 hours ago, Stratman said:

Thanks - the TLC guide explains the issue well and how to overcome it. Discussed with installer and he has already compensated for the derating by increasing cable sizes from the panels to a rotary isolator in the loft space.

Then all will be well - except! You need to think about how the cables come through the airtight layer as you will need to make that interface airtight as well. I used some squares  of EPDM with hole punched through smaller than the cable then pushed the cable through and sealed the EPDM to the airtight membrane once it was installed - it does mean pushing the cable through the airtight membrane so you need the end free to do it.

[Alan Ambrose]

Btw dc isolators are frowned upon these days unless the inverter doesn’t have its own dc isolation.