Polystyrene and conduit.

[johnston1991]

Hi, I haven't posted in a while so here goes,

I have been asked to to wire a couple of circuits into a garage conversion,

The customer has polystyrene from top to bottom, stud work (there is a layer of fibreglass between the polystyrene and plasterboard on the stud work) flooring loft ect, just looking for some opinions on the best way to go about the first fix with the issue of the chemical reaction between cables and polystyrene is plastic conduit everywhere a bit of an over kill or just the only way through it?

thanks in advance

 

[Evans Electric]

OK you are obviously aware of the problem Johnston , for any others benefit , if cables are in contact with polystyrene the polymers in the PVC start to migrate to the polystyrene , a black icky sticky substance becomes evident .

I would hazzard a guess that PVC conduit would be unaffected , I would think its the same PVC as plumbing and building plastics .

To be sure you need to check with makers .

 

[Apache]

Deke I think it's to do with the plasticisers used. They are added to the cable insulation to make it flexible, but not to the rigid PVC - hence uPVC windows (the u=un-plasticised).

 

[Evans Electric]

Thanks Patch, but doesn't the u mean resistant to UV light ?

 

[Sidewinder]

No mate Patch is right, the u is for unplasticised.

The material for conduit is the same as that for plumbers 32/40mm (etc.) waste pipework.

 

[tom1]

http://www.talk.electricianforum.co.uk/attachment.php?attachmentid=352&d=1261093686

had a pic of some in worse condition but you can see how its reacting with the pvc

 

[johnston1991]

thanks for that lads shall go with the plastic conduit

cheers