How to choose KNX bus cable: certified, LSZH or PVC
Once the walls are closed, cable is the part you cannot easily change, so check these three things before the first run is pulled. For KNX bus cable, that means a certificate number on KNX Association's list of certified cables, a shielded construction with published test values, and a low smoke zero halogen (LSZH) or PVC jacket that matches the project's fire specification.
What makes a cable a KNX cable
KNX Association describes KNX as an open standard. A KNX-certified cable has been tested against the KNX cable specification (KNX Volume 9/1), the results reviewed by a KNX-accredited test lab, and a certificate issued by KNX Association. Only then may the cable carry the KNX mark.
Neither a green jacket nor the letters KNX printed on it show that a cable passed those tests; a certificate number you can find on the KNX list does. KNX Association publishes a list of certified cables: take the number from the datasheet and check it against that list before you order. The list includes Kordz's LSZH KNX control cable under certificate no. 579/17212/20.
Why KNX cable is green
The KNX cable specification says that standard KNX TP (twisted-pair) cable is green, and that a non-standard cable must not be that green. Colour still proves nothing on its own: KNX Association's list also includes certified cables with white and black jackets. Check the certificate number, not the colour. Both versions of the Kordz ONE KNX Control Cable are green.
Construction that matters on site
A datasheet should let you check the cable, not only its name. Kordz gives one specification for both versions of its ONE KNX Control Cable:
- Conductors: four solid cores (20AWG x 2P) of annealed oxygen-free copper, 0.80 ± 0.015 mm, with polyethylene insulation, twisted together and colour-coded white, red, yellow and black.
- Shield (screen): a nonwoven fabric layer and an aluminium foil layer (Kordz specifies "Al-Mylar") aluminium side outwards, each with 125% coverage, plus a 0.408 mm tinned copper drain wire.
- Tests and rating: voltage test 4 kV for 1 minute, dielectric test 500 V AC for 1 minute, voltage rating 300 V.
- Resistance and temperature: nominal DC resistance 36.7 Ω/km at 20 °C; −20 °C to 70 °C in operation, −30 °C to 70 °C during installation.
The KNX cable specification includes a high-voltage withstand test between all cores and the screen, connected together, and the outer sheath: 2 kV for 5 minutes, or 4 kV for 1 minute. In some countries the 4 kV test is required. Kordz lists a 4 kV / 1 min voltage test for this cable.
What these figures give you: values to compare line by line with the project specification, and a defined core colour code (white, red, yellow, black) to terminate against. What they do not give: 4 kV is a test voltage, not a working voltage, and Kordz rates the cable at 300 V.
Running KNX next to mains cables
Follow the KNX installation guidelines and your local wiring regulations on separation from mains cables. Agree the bus route with the designer or consultant before first fix, so that separation is planned rather than improvised on site. Neither the shield nor the 4 kV test is a substitute for those rules.
LSZH or PVC: which jacket for which project
Kordz makes the ONE KNX Control Cable in two jackets. Conductors and shield are the same; the jacket, its fire rating and the KNX listing differ.
| LSZH | PVC | |
|---|---|---|
| Kordz part number | K17502-305M-GN | K17505-305M-GN |
| Jacket | Low smoke zero halogen (LSZH) composite | Polyvinyl chloride (PVC) |
| Fire classification / test in the Kordz datasheet | Construction Products Regulation (CPR) Dca s2,d2,a1 | IEC 60332-1 |
| KNX certification | KNX-certified, certificate no. 579/17212/20 (on KNX Association's list) | Kordz lists it as KNX-certified |
| Choose it when | the project specification, consultant or authority calls for low-smoke, halogen-free cable | the specification does not require LSZH |
Order the jacket your specification names. If the documents are silent, ask the consultant before the cable is pulled, not after.
Kordz ONE KNX bus cable: the two versions
We sell KNX cable whose manufacturer publishes a KNX certificate number and test values in its datasheet: the Kordz ONE KNX Control Cable, which Kordz describes as designed for systems technicians.
- Kordz ONE KNX Control Cable, LSZH, 305 m (K17502-305M-GN)
- Kordz ONE KNX Control Cable, PVC, 305 m (K17505-305M-GN)
The reel box, Kordz says, keeps the cable from twisting and curling, so it minimises snags and saves time during installation. The jacket carries metre marks for measuring each run. The KNX bus cable and connectors collection also has KNX bus connectors and 8-conductor micro connectors for junction boxes.
Order online and collect from our Dubai office. On your written request we hand the order to a carrier in the UAE at your cost and risk, as our shipping policy explains; buyers elsewhere in the GCC send their own courier or freight forwarder to collect. Availability and lead time are confirmed after you order. Technical support covers equipment bought from KNX Mall: quote your order number.
Checklist before you order
- Certificate: the KNX certificate number from the datasheet is on KNX Association's list of certified cables.
- Construction: conductor size, shield, drain wire and test voltage are stated in the datasheet.
- Jacket: the LSZH or PVC jacket matches the project specification, or the consultant has confirmed it where the specification is silent.
- Route: separation from mains cables follows the KNX installation guidelines and local wiring regulations.
- Temperature: the hottest part of the route is within the operating range (Kordz: −20 °C to 70 °C).
- Quantity and terminations: the 305 m reel boxes cover every run, and the bus connectors are on the same order.
Specifying a KNX project in the UAE? Order KNX bus cable for collection in Dubai.
KNX bus cable FAQ
How do I check that a KNX cable is certified?
Look up the certificate number from the manufacturer's datasheet on KNX Association's list of certified cables; colour and print on the jacket are not proof.
When do I need LSZH KNX cable rather than PVC?
Choose LSZH where the project specification, consultant or authority calls for low-smoke, halogen-free cable. Where the specification does not require LSZH, the PVC version to IEC 60332-1 is the alternative.
What is the difference between the LSZH and PVC versions?
The LSZH version (K17502-305M-GN) has a low smoke zero halogen composite jacket, CPR Dca s2,d2,a1, and is KNX-certified under certificate no. 579/17212/20, on KNX Association's list. The PVC version (K17505-305M-GN) has a polyvinyl chloride jacket to IEC 60332-1, and Kordz lists it as KNX-certified.
