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CABLING IN DATA CENTRES A guide for specifiers and installers

Cabling in data centres falls into three main categories – Data, Power and Building management. But they all have one thing in common: CPR. The Construcon Products Regulaon came into full force for cable in July 2017. Industry expert, FS Cables, explains what the new regulaon means in relaon to data centre cabling.

he Construction Products Regulation applies to almost all cables used within a civil structure (Buildings) and ranks them in one of seven classes, although only five are likely to be used (Class B2ca to Fca). Most cables sold in Europe for wiring buildings need to comply with the regulation. However, it is not a requirement for whoever is selecting the cables to choose a particular Class or even cables that are CPR compliant. It is up to the building designer, specifier, contractor, consultant or building owner as to whether they want to make it a contractual requirement. The new 18th edition of the wiring regulations also leaves it to individual choice to decide if CPR is even relevant and if so, which Class will be used.


Probably of more importance is to ensure the cables within a data centre emit minimal levels of toxic smoke and fumes when exposed to fire. In most cases, there are relatively few people in data centres but there is a vast amount of sensitive equipment with excellent air movement to aid cooling. This means that only cables classed as Low Smoke Halogen Free (LSHF) should be installed.

In conventional cables, PVC is widely used and when burnt gives off up to 28% of Hydrogen Chloride gas which combines with moisture in the air to create Hydrochloric Acid. This can be devastating to both people and equipment. With almost perfect air circulation through servers and other electronics, the acid coats everything including circuit boards and connectors. This risks random failures for years to come unless the equipment is replaced. However small the fire, even with good physical separation, the toxic fumes can still wreak havoc.

Taking the cables group by group, cables carrying data are probably the simplest and most straightforward. Whether the design incorporates fibre or stays with conventional copper almost all these cables are LSHF as standard and widely available on the market.

The classic Category cables are also offered from stock with CPR classifications including the highest Class B2ca level on Cat 6, Cat 6A, Cat 7 and Cat 7A. Fibre has for many years, used LSHF compounds and elements throughout their construction where the cables are intended for use in buildings so there should be no issues obtaining a suitable product.

Power cables can vary, with a lot of inappropriate cable being used, including flexible rubber cables, SY and standard PVC armoured cables, to provide power to the cabinets from a central PDU.

Power cables normally contain large volumes of insulation and sheathing materials so it is essential to make sure they do not present a hazard in the event of a fire. It is also important to recognise the potential effects of Electro Magnetic Interference (EMI) on the equipment and cables around. Shielding or screening the cables from the PDUs to the cabinets or servers can massively reduce the levels of Electro Magnetic Radiation. For low-frequency interference, copper braids work well whereas higher frequencies are better dealt with by using aluminium foils. That is why the dual-screened Niltox LF329 is so popular, Low Smoke Halogen Free throughout with foil and braid screening. Cables supplying the PDUs are often run in conventional LSHF armoured or SWA to BS6724. Building Management Systems are the final group and include lighting, security, HVAC, control and just about every other form of building wire.

Fortunately, the staple of most building wiring, Twin and Earth is now widely available in LSHF (6242B). Lighting and building control are also essential to maximise the efficiency of the building. As massive energy consumers, Data Centres need to be as “green” as possible so building control is a vital part. Many proprietary systems are available to help with this including systems from Honeywell, Simmtronic, Crestron, Control 4, Thorn, Mode and many more including open source systems such as KNX. FS Cables stock cables for all the above systems in LSHF and CPR-compliant versions.

Security systems, providing access control, CCTV and monitoring all need cabling back to central control points. The range is diverse to say the least with coax’s and Category or Lan cables for CCTV, Belden style twisted pairs and conventional alarm cable for access control or monitoring systems as well as proprietary systems including Cotag. All cables are available in LSHF and should be specified as such.

One point to consider is that a PVC cable over sheathed with an LSHF jacket will still emit toxic fumes when the jacket burns through, as will a cable with PVC insulation, so it is critical to specify the cable must be LSHF throughout. CPR does not cover the toxicity or smoke generated at the lower Class’s making LSHF even more critical in the specification.

A sentence or two of warnings about CPR. Due to the very high testing and ongoing inspection costs of the higher Classes (Class Cca and B2ca) it is not commercially viable to test many specialist or low volume cables. So, specifying CPR without a Class is meaningless and it is unwise to specify a class without first checking the availability of the product, or you could find that you have a very safe but completely unachievable design! Cables designed to survive or continue to operate in the event of a fire (Circuit Integratory Cables) are exempt from CPR. This includes conventional fire alarm cables such as FP200 and Draka FireTuf, Fire resistant data cables such as Draka FireTuf Data, Fire resistant fibre and fire-resistant power cables such as Prysmian’s FP600. FS Cables stocks more than 600 CPR compliant specialist cables many of which are also LSHF throughout. VISIT OUR WEBSITE: BUILDING SERVICES & ENVIRONMENTAL ENGINEER SEPTEMBER 2018 39

It is important

to ensure that cables within a data centre emit minimal levels of toxic smoke and fumes when exposed to fire. In most cases, there are relavely few people in data centres but there is a vast amount of sensive equipment with excellent air movement to aid cooling. This means that only cables classed as Low Smoke Halogen Free (LSHF) should be installed.

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