The experts at ECA explain more about the different types of control cables and why a new certification scheme should help to improve the quality of cables being sourced and used.
Control cables are found in a vast array of industrial and everyday applications. These products are flexible, interconnecting and used to measure, control or regulate equipment like assembly or production lines, and to provide support for their associated computer units and work processes.
Control cables are used when a direct connection to the controlled object is impossible. As such, control cables can occupy an intermediate position between communication cables and power cables.
A new BASEC certification scheme
Currently, these control cables are not governed by any specific standards, which can often confuse manufacturers, installers and users. In response to demands from the marketplace to help address this problem, BASEC has launched a certification scheme to encourage standardised and consistent levels of quality for control cable product ranges. Reflecting industry requirements, the new scheme refers to YY, SY and CY control cables.
What do YY, SY, and CY mean?
YY, SY and CY control cables are some of the most commonly used cables for applications such as industrial automation, railways infrastructure and more. The cables transmit information about the location, status and operating condition of an industrial component being controlled.
YY, SY and CY originate from the European Committee for Electrotechnical Standardisation (CENELEC) naming conventions, where the first characters refer to the following:
– ‘Y’ = unscreened
– ‘S’ = steel wire braid
– ‘C’ = copper braid
The second character, ‘Y’, in each group refers to the material types – usually PVC – but the cable sheathing may also be a low smoke type. SY control cable may also be referred to as flexible, braided, flex or instrumentation control cable.
Types of control cable
YY cables are unscreened, flexible control cables available in various cores and conductor sizes – suited to environments with light mechanical stress.
SY cables have a braid of galvanised steel wire (GSWB); these cables are suited to installations with medium to high mechanical stress.
CY cables are screened, flexible control cables with construction options similar to YY types but they include a tinned copper braid over the bedded, laid up cores – this extra braid adds protection against external electromagnetic influence.
All control cables are available as PVC or low smoke emission versions (LSHF), depending on their application. Low smoke cable variations should be installed for environments where safety is critical, to limit the danger to life or equipment.
Compliance with the Wiring Regulations
Under the IET Wiring Regulations (BS 7671), YY, SY and CY control cables are not recommended for use as part of a fixed installation. The IET’s supporting guidance states: “For the purposes of ensuring compliance with BS 7671, the installation and use of non-standard cables, such as SY, CY and YY cables is discouraged.”
This means that a deliberate decision not to fully comply with the Wiring Regulations by using control cables in a fixed installation, must be noted as a departure. Any use of a custom, non-standard, or partially compliant cable must be declared and assessed, and it must be ensured that the degree of safety isn’t compromised.
Some manufacturers claim that YY, SY and CY cables comply with the general requirements of the BS EN 50525 series (flexible cables) but these designs differ from the requirements of the mentioned standards. For example:
The BS EN 50525 series
BS EN 50525-2-11 is the British Standard for PVC flexible cables, but it has no provision for any braid. Therefore, braided cable, such as SY cable, can’t conform to this standard.
In 2017, it was reported that the insulation and sheath thicknesses of cables designated YY, SY and CY often have lower insulation and sheath thicknesses in comparison with the BS EN flexible cables. Therefore BS EN 50525-2-11 is not an appropriate standard for YY, SY and CY cables.
Some YY, SY, CY cables claim to be made to continental standards, though it is not clear what these standards are.
BASEC Standard and Certification Scheme
As an authority and preferred testing and certification partner to the worldwide cable industry, BASEC is regularly contacted to support and advise on control cable products’ comparability and application.
The BASEC scheme offers the cable industry and its users a way to improve and evidence the levels of quality and safety that the products manufactured, specified or sourced hold. There is presently no referenceable standard for this, hence the reason these cable products are often a debated hot topic.
The scheme comprises six BASEC specifications: BA 1411, BA 1413, BA 1415 for PVC design and BA 1412, BA 1414, BA 1416 for LSHF design.
The new certification scheme is relevant to cable products up to and including 300/500 V, with a maximum conductor operating temperature of 70°C. Where applicable, standards EN 50525-1 and EN 50565-2 will be referenced in conjunction with the control cable scheme document.
BASEC is known within the industry for rigorous certification, factory auditing and testing schemes, which work continuously to improve the quality and safety of cable products at manufacturing sources. With this in mind the new scheme has been developed, offering an all-inclusive testing programme for this widely used and barely regulated range of cable products.
Get more technical support and advice from the ECA here