Use milk bottle carton for conduit for PVC cable?

[lucky67]

Ok sure I'm going to be flamed for this but...
I'm using polystyrene sheet to insulate a wall in a room in the eaves...
I have a few PVC power cables that I will have to move (I've read that polystyrene causes the PVC to become brittle)...most of them are for the 2 lights in there but there are 2 that I have no idea what they are....

Now I was going to run them through some type of plastic conduit ...but then I read that that might cause problems too...so my next solution was to attach a piece of wood/plasterboard to the top of the polystyrene and then cable clip the cables to this...(so they run where they do now just 75 mm or so further off the wall)...
The only problem would be where the unidentified cables disappear through a hole into a plasterboard cavity - I'm looking for something to line this hole with to keep the cable from touching the polystyrene -plasterboard or wood would be a nightmare to cut and fit to line such a small gap so I was thinking that maybe I could use a piece of a milk carton (HDPE) or my other thought was a cut down piece of waste water pipe...
any thoughts???
Also if I do end up using plasterboard/wood to make a tunnel - would it be really bad to stick a little bit of mineral wool in there to stop the draughts?

 

[bugsy]

Is this a wind up!

 

[Marvo]

First I've heard of polystyrene insulation making PVC brittle....maybe insulation in general could make cables brittle if you don't derate their current capacities accordingly and they overheat.

Your idea of making a tunnel in the insulation then filling the tunnel with ....more insulation...kinda went over my head. Anyway there's a product around called 'spirawrap' which does as its name suggests and sounds like it might help you do whatever you're trying to do.

Edit; Here's a link for you.

 

[R1CH-G]

Flexible conduit - slit and slide over the cable, if you need to insulate, intumescent mastic will stop breezes. To make it look pretty, get those slip on ferules that plumbers use over the pipes!

EDIT: Presume that you can't shift the cable into conduit!

 

[Deleted member 26818]

It leaches the plasticiser out of the PVC insulation.
To be honest, it's more of a problem where Polystyrene pellets are used, where cables get too hot and where the cbles are subject ti movement or vibration.
As the cables you are installing are not completely surrounded by insulation, and are unlikely to be moved; unless they are subject to severe vibration or a seriously underated there should be no real cause for concern.

 

[Marvo]

It leaches the plasticiser out of the PVC insulation.

You mean on a molecular level? Do you have a link for info, I'm interested to read up on this, Thanks.

 

[Deleted member 26818]

http://www.generalcable.co.nz/Technical/10.1.1.1.pdf
I'm certain there are others, this is just he first one I googled, hint hint.

 

[R1CH-G]

I thought it was something to do with the plasticisers in PVC and migration?

 

[Marvo]

Thanks SpinLondon, and sorry, no hints needed I was just being bone idle lazy.
Do the 17th edition regs have anything to say about preventative measures?

 

[Deleted member 26818]

No they don't, other than in general terms, good workmanship, external influences etc etc.

 

[lucky67]

Thanks -it isn't a wind up...
As I understand it as long as the cable doesn't touch the polystyrene it is safe...just need some kind of barrier...even air is good enough (but not possible in this situation).
And read something about running cables along conduit can effect the rating or something - and may cause overheating) - you can't just stick cables in a conduit????
I'm happy with running along wood/plasterboard - basically that's what it does now - it is just this bit - only for the width of the polystyrene -about 10 cm.

I don't have access to the cables at the other side of the wall - so whatever I use I have to be able to wrap round the cables I can see and then push along through the hole to line it (hence my plastic milk carton - thought I could cut a strip and make a tube around the cable (fix it together with tape (insulation/duct/anything))...but then wondered if HDPE has a detrimental effect on cable too...
Will look at flexible conduit - think that will do the same job - but I only need 10cm!

 

[grantr37]

Polystyrene insulation is illegal now and has been since about 1988, its a danger in the event of a fire.....dont use it...use foil backed drywall/gyproc/plasterboard if neccesary

 

[Simlec]

Materials used

The three most common types of cavity wall insulation used are:

1. Blown mineral fibre
2. Polystyrene beads or granules
3. Urea formaldehyde foam

 

[grantr37]

Materials used

The three most common types of cavity wall insulation used are:

1. Blown mineral fibre
2. Polystyrene beads or granules
3. Urea formaldehyde foam

The cavity wall insulation "pellets" have an entirely different formulation as opposed to the sheet polystyrene.....you can use that stuff(sheet polystyrene) outside under roughcast coatings but not indoors where it will emit toxic chemicals into the air in the event of decomposition at high temperature (in a fire) and it was made illegal to use it in interior insulation and as the filler/padding for furniture many years ago.
You may remember (and sometimes still see in blocks of flats) the foam tiles that were glued to ceilings, as it was thought that they were visually pleasing and had good insulation properties.....I remember years ago they used to sell Polystyrene decorative surrounds for Light ceiling Roses that could be overpainted, these got banned as well....

 

[grantr37]

And I have a friend who is an insulation specialist and runs his own company doing it, he sprays insulation and Fire resistant insulation coatings at refineries and on oil rigs etc with machinery that I helped him import from the states....