Thermoplastic-sheathed (TPS) cable underpins most low-voltage fire and data wiring in Australia. One product code on the purchase order hides three constructions tuned to different duties. Pick the wrong one and the inspector may order a complete re-pull. The notes below, prepared for sparkies and fire-system installers, explain why flat red, striped and twisted TPS exist, outline the relevant clauses in AS/NZS 5000.2, AS/CA S008 and AS 1670.1, and list site checks that keep projects on time.
What defines TPS?
AS/NZS 5000.2 describes TPS as 0.6/1 kV copper conductors insulated and sheathed in PVC or low-smoke zero-halogen (LSZH) thermoplastic, either flat or twisted. Core sizes of 1.0 mm² and 1.5 mm² dominate fire-alarm work; a pilot earth is optional under AS 1670.1 unless the circuit exits a fire-rated enclosure. When the pair is twisted, AS/CA S008 also applies because the cable behaves like a communications link.
Colour coding at a glance
- Flat red TPS cables — detection loops, local sounders, relay inputs.
- Flat red with white stripe TPS cables — EWIS speaker runs or intercom loops where visual separation from detection wiring helps with fault-finding.
- Twisted TPS cable — noise-sensitive balanced lines such as talkback microphones, digital speaker loops and panel data buses running past heavy mains.
When to stay with plain flat red
Flat red remains the cheapest and easiest to handle. A 100 m drum weighs about 10 kg, so one tech can lift it onto a ladder rack. Because the cores sit parallel, conduit fill stays low and loop resistance rarely causes trouble provided the run stays under 300 m. Check the print legend for “V-90HT” (or “LS0H” if low-smoke) and the manufacturing licence number before signing the delivery docket.
Adding the white stripe
A fused white stripe costs a few cents more per metre but saves hours in riser cabinets. Techs can trace detection, occupant-warning and talkback circuits quickly, and asset owners like the clear demarcation when future stages are added. Electrical specifications mirror the plain red product, yet stock levels are thinner—allow a three-day lead if the site needs LSZH.
Why choose a twisted lay?
Twisting equalises the electromagnetic field around each conductor so external noise is cancelled. On EWIS talkback, a stray 50 Hz hum will push a commissioning report straight back across the desk; twisted TPS almost always solves it. Expect a bulkier cable—around 8 mm across flats for a 2C 1.5 mm²—and a lower tensile rating (45 N per mm² of copper). As the twist must stay intact, joints are crimped rather than soldered, and installers leave slack to avoid unlaying.
Logistics: drums, copper clauses and storage
For any job larger than 1 km total run, lock the rate no earlier than two weeks out from delivery to avoid margin swings. Standard drums come in 100 m and 500 m lengths; twisted variants top 60 kg for the larger drum, so plan forklift access. Store drums upright and unspool with a payout stand to avoid kinks that violate the 8 × OD installed bend radius.
LSZH versus PVC
Hospitals, tunnels and rail stations often demand LSZH to cut acid smoke during an evacuation. Expect a 15–20 % premium and stiffer handling. Pull slowly, use wide-radius elbows, and specify LSZH fixings so the entire route shares the same smoke rating.
Mechanical limits
| Parameter | Flat & striped | Twisted |
| Maximum pull tension | 50 N / mm² of conductor | 45 N / mm² |
| Bend radius (installed) | 8 × OD | 8 × OD |
| Bend radius (during pull) | 6 × OD | 6 × OD |
Field tests before the certifier arrives
- Loop resistance: ≤0.4 Ω on detection loops, ≤0.2 Ω on speaker circuits if amplifier wattage demands tighter limits.
- Insulation resistance: ≥1 GΩ at 500 V DC for 60 s conductor-to-conductor and conductor-to-earth.
- Continuity: Confirm both cores and any pilot earth back to the panel.
Record the readings in the commissioning dossier along with drum numbers and test-instrument calibration certificates.
Quick-reference table
| Cable type | Typical application | Key standard clauses | Watch-outs |
| Flat red | Smoke loops, relay inputs, local sounders | AS/NZS 5000.2; AS 1670.1 §3.18 | Cap spare cores; respect bend radius |
| Flat red + white stripe | Speaker, intercom and staged-evacuation lines | AS/NZS 5000.2; AS 1670.1 §3.22 | Price premium; LSZH may be special-order |
| Twisted TPS | Talkback mic loops, balanced audio, data buses near EMI | AS/CA S008; AS 1670.1 §3.27 | Larger diameter; lower pull tension |
Final checklist
- Match sheath colour to drawings—striped means striped all the way.
- Lock copper pricing close to ship date.
- Choose LSZH when the building code or fire engineer mandates it.
- Stay within tension and bend limits.
- Save loop and insulation results for every circuit.
With those steps in place, the TPS installation will meet the standards and pass commissioning without drama.
