UL approval up to 600 Volts for data cables

Why users are increasingly demanding higher dielectric strength

Data cable users are increasingly demanding voltage specifications and approvals from the American testing and standardization organization Underwriter's Laboratory (UL). However, data cables are not designed for the transmission of heavy current and are not used for this purpose in practice. The reason for this trend lies elsewhere – and has its origins in the installation of so-called cable ducts.

Cable ducts are mainly used in the cabling of buildings, but also in mechanical engineering and industrial automation. They are supporting structures for cables and electrical wires and are usually made of steel or stainless steel sheet or plastic. The ducts often have multiple spaces in which installers can lay cables with different functions and voltages separately. There are shielding plates between them to prevent interference - for example from electromagnetic waves. Depending on the installation conditions, the cable tray can be part of the machine cabling or part of the building cabling – this is determined by the UL inspector.

When a new data cable is laid in a production hall with an existing support system, it may happen that a relevant space in the cable duct is not intended for this purpose or is already fully occupied. In that case, the installer must inevitably lay the cable in the next room - where there are often power cables with a dielectric strength of up to 600 volts, and in rare cases even 1,000 volts.

Same dielectric strength for cables laid together

This is where the UL standard comes in: it requires that all cables laid in a room have the same dielectric strength. Although a data, sensor or bus cable never operates at 600 volts, the dielectric strength must be stated on the label. Otherwise, the inspector may deny approval, or the installer may need to retrofit protective conduit or replace the cable to obtain approval from the certification company. However, the UL listing UL444, which usually applies to building cabling, expressly prohibits the printing of voltage information on communications cables – a fact that is contrary to the wishes of users, who are increasingly demanding this very information.

To meet the requirements of its customers, HELUKABEL has, for example, provided its Ethernet cables of the PROFInet series with additional UL certifications, so-called AWM styles (Appliance Wiring Material). These guidelines, which have their origins in the cabling of machines and equipment, ensure the desired higher dielectric strength of the cables and enable the corresponding printing required for successful approval. However, this does not allow the user to simply lay data cables together with power cables. The UL approval does include a dielectric strength test, but not an electromagnetic compatibility (EMC) test. Therefore, despite the extensive certification, data and power cables should be laid separately or remotely if possible. For example, if a joint installation is unavoidable for space reasons, the installer must perform an EMC test to avoid possible interference.

UL specifications also required for machine cabling

Whether a cabling system is intended for a machine or a building, the inspector determines which standards apply. In machine and plant construction, drag chains are often used for laying both power and data cables – in fact, here they are no more than a mobile form of a cable rack. However, UL does not have a set standard for drag chain configuration. Here much is left to the inspector's discretion.

However, in recent years, approximately 30 percent of UL inspectors have moved the requirement for the same voltage range from cable trays to machine cabling and drag chains. Increasingly, if cables are not laid separately or cannot be laid separately, the same dielectric strength is required for data and power cables. That is why the demand for cables with the associated UL approval is also increasing. With its extensive portfolio of data, network and bus cables, which are approved according to both UL444 and AWM, HELUKABEL offers the optimal solution for every application – including the dielectric strength required by the UL standard.