SPARKS!: On this site, you will find useful Industry contacts, electrical gadgets, how to guides, a wide range of electrical tips and tricks and much more to help you make your career a success!

by Mark Coles, IET

The IET has a busy technical helpline and a number of calls were taken on the following topic.

Question: Can bluesheathed cable, made to BS 6500, be used for 230 V a.c. single-phase supplies to equipment in temporary use?

Answer: Yes, but not at temperatures lower than +5°C. The following is intended to clarify. 

Introduction

It is common to see bluesheathed flexible cables, sometimes referred to as ‘Arctic’ cable, used on temporary low-voltage installations, such as construction sites, fairgrounds and musical events. In addition to blue, this type of cable is available in many different colours, such as yellow and orange and some cables even have the word ARCTIC embossed throughout the length. Not all cables are suitable for all applications. It is, therefore, important to establish the suitability of the cable in question prior to selection by referencing the standard to which the cable is manufactured. Two standards for flexible cable will be considered here - BS 7919 and BS 6500.

Cables to BS 7919

Electric cables — Flexible cables rated up to 450/750 V, for use with appliances and equipment intended for industrial and similar environments

Ordinary duty low temperature PVC insulated and sheath 300/500 V flexible cable, manufactured to BS 7919 Table 44 (not harmonised), commonly referred to as 3183A (Arctic Grade Flex), was specifically designed and, hence, included in the British Standard, for use at 110 V a.c. from centre tapped transformers (55 V - 0 - 55 V).

The cable is suitable for installation and handling down to a temperature of -25°C, e.g. suitable for construction site installations and is often seen in use on temporary road works for supplies to traffic lights; Table 7B from BS 7450, refers. Note that cables to BS 7919 Table 44 have not been harmonised to European HDs. This is because the use of 110 V a.c. supplies from centre tapped transformers (55 V - 0 - 55 V) is a UK only practice and is not recognised or practised elsewhere.

BS 6500

Electric cables - Flexible cords rated up to 300/500 V, for use with appliances and equipment intended for domestic, office and similar environments

Ordinary duty PVC insulated and sheath 300/500 V flexible cable to BS 6500, commonly referred to as 3183Y (harmonised number H05VVF), is suitable for use at 230 V a.c. The cable is suitable for installation and handling down to a temperature of +5°C.

Neither BS 6500 nor BS 7919 requires the cable to be marked with the word Arctic. Should any cable be marked as Arctic, it is solely the responsibility of the manufacture to justify any such claim. The only PVC flexible cable that could be classified as being suitable for low temperature use is a cable to BS 7919 Table 44 as it can be installed and handled down to a temperature of -25°C; it would seem logical that only this cable would/should have the term ‘ARCTIC’ marked on it.

For more info on wiring regulations visit www.theiet.org/wiringregs