TPS/PVC cables in contact with polystyrene products

TPS/PVC cable insulation can be compromised by a chemical reaction if it contacts polystyrene. Make sure you check the insulation is undamaged before installing this cable and always follow the cable manufacturer’s instructions.

The plasticiser in cable insulation PVC to make it flexible and tough is not chemically bonded to the PVC and will slowly leach out of the cable over time. The process of cable losing plasticisers increases when the cable is in contact with other materials, such as polystyrene and polyurethane. The leaching of the plasticiser will cause the cable’s PVC material to become harder, brittle, and prone to cracking. This could mean live conductors are exposed, with the potential for electric shock or fire.

One significant factor that affects the rate of leaching is the size of the contact area between the cable and polystyrene. The larger the contact area, the quicker the rate of plasticiser leaching out. The rate of the cable’s deterioration will vary with the installation conditions.

It may mean that the cable becomes unsafe to work near during maintenance, repairs or building alterations, so the cable may need to be replaced sooner than expected.

Typical installations where cabling was used in conjunction with polystyrene products are:

• caravans
• cold rooms
• transportable buildings
• wall or roofing insulation material.

New installations

Select a cable with protective sheath material that the manufacturer confirms can be installed in contact with materials such as polystyrene and polyurethane. Alternatively, cables should be installed so there is no direct contact between the cable and polystyrene.

If you’re installing cables that haven’t been proven suitable for direct contact with polystyrene or polyurethane, either:

• install the cable in a suitable conduit
• leave an air gap between the cable and the polystyrene
• apply a suitable barrier between the cable and the polystyrene.

Existing installations

If you identify a cable in contact with materials such as polystyrene and polyurethane, check to see if the cable has become hard and brittle, and if it has, replace it. If it hasn’t become hard or brittle, consider actions to remove the contact.