Sealing around electric cable

[Stones]

I've got to seal around some electric cables where they go from insulated to uninsulated space.  IIRC the PVC sheathing around electric cables doesn't react well with XPS, or it may be EPS (can't remember).  It may also suffer when in contact with other materials / products.  Can somebody refresh my memory as to what products I need to avoid using to seal around cables - expanding foam, silicone, caulk?  If I wrap the cable at the relevant point with electrical tape, can I avoid the PVC degradation problem?

[Temp]

In a word, Yes.

 

PVC reacts with EPS and Polyurethane. That's why mains cables are frequently wrapped in plastic bags before they are put into the EPS packaging.

[Stones]

Managed to speak to the electrician this afternoon when he stopped by the site.  He confirmed the issue with EPS, and advised that where he had run cables down the face of ICF blocks, building paper would be fitted behind to prevent the cable coming into contact with EPS.  He did say that they used to put cables in conduit, but had moved away from this as it slowed down plasterboarding.  Interestingly, he said using expanding foam round cable penetrations was okay, as was using decorators caulk.

[Temp]

To be safe he should also wrap the cables if using expanding foam as most of that is polyurethane based...

 

http://www.generalcable.co.nz/getattachment/0ebda90b-b4f8-43ae-b622-c9280295116b/PVC-Cables-in-Contact-with-Polystyrene-or-Bitumen.aspx

 

Commonly used PVC plasticisers tend to exhibit solubility in polystyrene and polyurethane insulating materials, As a result of this there will be migration of plasticiser from the PVC compound where there is a direct contact between the two materials, this causes the PVC on the cable to become harder and more brittle.

 

When using cables without non migratory plasticiser it is recommended that there be no direct contact between the cable and the polystyrene, this can be achieved by installing in a suitable conduit, leaving an air gap or using a polyethylene or polypropylene tape between the cable and the insulation.

[Stones]

In a fixed position, i.e. one where there is no movement of the cable, does the fact that the cable may become harder and more brittle really matter?  

[Onoff]

1 hour ago, Stones said:

In a fixed position, i.e. one where there is no movement of the cable, does the fact that the cable may become harder and more brittle really matter?  

 

Under load cables heat up and expand. If you have cracked, brittle insulation then conceivably repeated expansion could cause migration of the copper cores. Taking it to the nth degree I know but why take the chance for the sake of a bit of protection. You could also leave the brittle, cracked cable vulnerable to say water ingress or other mechanical damage.