Requirement to protect PVC cables from polymeric insulation materials
NT WorkSafe reminds the electrical industry, electrical contractors and electrical workers of the requirement to protect PVC cables from contact with polymeric insulating materials such as polystyrene and polyurethane as required by the wiring rules (AS/NZS3000).
What is the issue?
A chemical reaction can occur overtime when Polyvinyl chloride (PVC) contacts with polystyrene and polyurethane, which causes the PVC insulation to become hard and brittle.
When PVC cables are installed in contact with PVC insulation which may occur in demountable type buildings or in cool room type panelling the plasticiser of the cable may migrate out of the cable into the polymeric insulating material. Although this process usually happens over a long period of time, the cable insulation will become hard and brittle which may cause the failure of the PVC cable insulation and result in fire or energisation of metallic building elements.
What is required?
When installing, PVC type cables in contact with polymeric insulating materials, electrical contractors and workers must:
- Use a PVC cable that is manufactured and identified as being suitable for installation in contact with polymeric insulating materials. These cables usually have a purple sheath and are commonly known as non-migratory type cables, or
- Use conduit to prevent direct contact between the cable and polymeric insulating materials.
Some cable manufactures may allow the use of polyester or polypropylene separation tapes to prevent contact between the cable and the polymeric insulating material. Before doing so, get approval from the cable manufacturer and keep a record such approvals with the relevant certificate of compliance.
Both connectable and fixed electrical installations require one of the above control measures to prevent deterioration or hazardous degradation of PVC type cables.
Relevant Australian Standards
- AS/NZS 3000:2018 Electrical installations (3.3.2.5 Corrosive or polluting substances)
- AS/NZS 3001.2:2022 Electrical installations - Connectable electrical installations and supply arrangements, Part 2: Connectable electrical installations (3.7.4.2 Cables in contact with polystyrene or polyurethane)
Reminder
It is a requirement under the Regulation 85 of the Electrical Safety Regulations 2024 that all electrical work complies with the wiring rules. If you require further assistance, please contact the NT WorkSafe Electrical Safety Unit to discuss your concerns.