Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This Question of the Day, concerning potentially hazardous use of SY braided extension cables with 16A plugs outdoors, is answered by BASEC:
Answer: Don't use standard plugs - you are correct in identifying the hazard!
Standard indoor 13A plugs are not designed to be used with braided cables, but only with three core (brown, blue, green/yellow) flex. Standard industrial plugs and sockets are, likewise, not generally designed to accommodate a steel braid.
If it is felt that a steel braided flexible cable should be used because of the greater physical protection offered (such as SY type), then an appropriate plug / socket system must be used, with the appropriate gland and termination for the braid. These plugs are available from specialist suppliers. The braid needs to be bonded to earth.
If the braid is cut off and taped outside the plug, then there will be an additional mechanical bending strain on the inner cable at this point, because the rest of the cable is stiffer, potentially leading to cable failure where it enters the plug. There is also the potential for a loose un-bonded braid to come into contact with live terminals inside the plug.
In most cases, a standard heavy-duty un-braided flex should be sufficient (assuming it is a normal centre-tapped 110V application). Cables should be regularly checked for damage and replaced if necessary.
Individuals or employers supplying or condoning the use of inappropriate installations should be warned of these hazards.
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