Rallison RS-485 Communication Cable is a 300/500 V grade twisted-pair data cable with a nominal 120 Ω characteristic impedance, purpose-built for Modbus, BACnet and other RS-485 field bus networks used in building automation risers. Its controlled twist and screening keep signal integrity high over the long point-to-point and daisy-chain runs typical of building management system networks.
Cable Construction
- Conductor: bare annealed electrolytic copper, stranded, Class 2 per IS 8130
- Insulation: PVC or polyethylene insulation on each core, closely twisted in a pair to a controlled lay length for 120 Ω nominal impedance
- Core identification: one pair colour-coded (typically white/blue), with drain wire where an overall screen is fitted
- Inner sheath: PVC inner sheath (bedding) over the twisted pair
- Armour: none; aluminium-mylar tape screen with drain wire
- Outer sheath: PVC outer sheath, FR/FRLS grade as ordered
- Cable colour: grey (standard); other colours on request
Cable Design Parameters
| Part Number | Nominal Cross Section (sq. mm) | No. of Strands (Cu) | Insulation Thickness (mm) | Inner Sheath Thickness (mm) | Outer Sheath Thickness (mm) | Approx. Overall Diameter (mm) | Approx. Weight (kg/km) |
|---|---|---|---|---|---|---|---|
| R-485-1P05 | 0.5 | 16/0.20 | 0.4 | 0.4 | 0.9 | 5.8 | 48 |
| R-485-1P075 | 0.75 | 24/0.20 | 0.5 | 0.5 | 1.0 | 6.6 | 62 |
[CONFIRM: Overall diameter and weight figures are nominal design values — verify against Rallison production data before publication.]
Electrical Parameters
| Part Number | Nominal Cross Section (sq. mm) | Conductor Resistance at 20°C (Ω/km, max) | Characteristic Impedance (Ω) | Insulation Resistance (MΩ.km, min) | Test Voltage (V, 5 min) |
|---|---|---|---|---|---|
| R-485-1P05 | 0.5 | 36.0 | 120 | 10 | 1500 |
| R-485-1P075 | 0.75 | 24.5 | 120 | 9 | 1500 |
Standards & Compliance
Conductor stranding follows IS 8130, and cable construction and testing follow TIA/EIA 568-B/C practice for twisted-pair data cabling adapted to a 120 Ω field bus design. Materials are RoHS and REACH compliant. [CONFIRM: compliance certificates]
Applications
Used for Modbus and BACnet field bus wiring linking building management system controllers, sensors and actuators along vertical risers and horizontal runs in commercial buildings, airports and process control installations, and generally for RS-485 data communication in automated plant networks.
Ordering Information
When ordering, alongside the part number please specify: conductor material and class, insulation type, sheath category (FR/FRLS/LSZH), armour preference, drum length.