BASEC News

Cables in the Cold

12/10/09
With winter fast approaching it is worth reviewing the special types of cable that are designed especially for cold environments, and remembering that special measures should be taken when handling ordinary cables in cold conditions.

Just as plastic materials get softer when they are used in a warm environment or heated, they become less flexible when subjected to cold conditions.  Under extreme cold, cable insulation and sheathing can crack or even disintegrate, resulting in a short circuit or electric shock.  In these circumstances it is important that the correct type of cable is used.

When laying cable in unheated surroundings, it is important to check the cable’s minimum installation temperature.  As a rule of thumb, it is safe to handle most installation cable types down to about 0 °C, or the freezing point of water.  Below this temperature damage could occur during installation.  However, once installed, most fixed installation cables may be energised and used at temperatures below zero, because they self-heat due to residual conductor resistance.

Where cables need to remain flexible at temperatures below 0 °C, special polymers are used.  The best known example of this is “arctic grade flex”, made to BS 7919, commonly used on construction sites and in other cold-related applications such as cold stores.  Yellow-sheathed cable is conventionally used for centre-tapped 110V applications, with blue sheathed for 240V use.  BASEC conducts tests such as cold bend at -40 °C on these cables to demonstrate acceptable performance.

In parts of Europe where the temperature is below zero for much of the wintertime, special cable types are recommended for outdoor installations, including lighting and for ice removal.  These include the H07V3 types and certain rubber cable types such as H05RR-F.  Again, it is important that the specifications and compliance are checked if these cables are to be used below zero.

Some cable that does not comply with BS 7919 can be found on the market, often labelled as ‘arctic grade’, but with inadequate cold temperature performance.  If installing such cable it is wise to check the specification is to the correct British or European standard.

Further information and assistance is available at www.basec.org.uk, technical@basec.org.uk, or contact BASEC directly on 01908 267300.

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