extension reel
An extension lead that rolls up, usually into the socket end, which in some cases has more than one socket on it (often 2 or 4).
extension reel: portable cable storage that unwinds to length
An extension reel is a motorized or manually wound drum that holds electrical cable coiled under tension, allowing you to deploy exactly the length of cord you need for a job. The cable feeds from the center of the reel through a guide, and the socket block (carrying one or more outlets) sits either at the reel's hub or at the cable's working end. Most common models in industrial and construction use store between 25 and 50 metres of cable, though domestic versions run shorter. The reel itself is usually plastic or light steel, sized to fit through doorways and down stairs.
The socket block mounted on the reel end typically has two or four sockets rated between 13 amps and 16 amps in UK and European standards. Some reels feature a thermal cut-out built into the socket block to protect against overload; others rely on the building's main circuit breaker. Automatic reels wind the cable back in by spring or electric motor when you release the cable; manual reels require you to turn a handle. Automatic types are faster to pack away but cost more and can jam if the cable tangles during operation.
Reel cable is usually PVC-sheathed 1.25 mm or 1.5 mm twin-and-earth or three-core flex, rated for flexing. The cable must be properly graded for outdoor or damp use if you are working on site; standard indoor PVC will degrade quickly in wet conditions or direct sunlight. Heat is the primary failure mode: coiled cable loses its ability to dissipate current, so overloading a reel carrying a live load causes the copper to overheat, melting the insulation from inside out. Never run power tools continuously at full load through a fully wound reel.
Why reels matter on site
A reel eliminates trip hazards and cable damage that loose coiled cable creates, and the socket block gives you outlet access without a separate adaptor board. On construction sites and in warehouses, reels take up minimal floor space when wound, and they move easily. The disadvantage is that automatic reels cost two to three times what a basic extension lead costs, and the motor and gearing add failure points if subjected to dust or impact.
Extension reels sit between cheap disposable leads and fixed site wiring. They are standard on hire fleets and in mobile workshops, and they appear in regulations for temporary electrical installations on building sites. Choosing one requires matching cable length to your site layout, socket count to your tool count, and amp rating to your peak simultaneous load. A reel wound fully under load will always present lower electrical efficiency and higher thermal risk than the same cable fed out loose.