Extension Leads and Cable Reels for Trade: Selecting the Right One for Site Use

Extension leads and cable reels are site essentials. Every electrician, plumber, and builder uses them daily. But pick the wrong one — wrong length, wrong load rating, or wrong type for the environment — and you're either tripping breakers or, worse, creating a fire risk. This guide cuts through the options so you know what you're buying and why.

Extension Leads and Cable Reels: What's the Difference?

Both do the same basic job — they extend the reach of a 13A mains supply — but they're built for different use cases.

Gang extension leads are flat, fixed-length leads with multiple sockets. They're the right choice when you're working in one spot: a workshop, a kitchen fit-out, a bathroom first-fix. You plug in, you work, you pack up. Options like the Daewoo 6 Gang Individually Switched Extension Lead 2m give you six outlets with independent switches — useful when you've got multiple tools plugged in and don't want to be crawling behind a unit every time you need to kill power to one tool.

Cable reels are for mobility. A 15m, 20m, or 25m drum that unwinds as you move around the site. They're standard kit on any job where you're moving between rooms or up and down a ladder. The SMJ 4 Gang Extension Reel 13A 15m and the Faithfull Open Drum Cable Reel 240V 13A 20M are the kind of drums you'll see on the back of most tradesmen's vans.

Load Ratings: Wound vs. Unwound — This Is Critical

This is the bit that most people get wrong, and it's a genuine fire hazard. Cable reels have two load ratings:

• Fully unwound: 13A maximum — that's 3,120W. You can run a power tool, a site light, or a power drill on this.
• Wound (coiled on the drum): typically 4A maximum — around 1,000W. When cable is coiled, heat builds up in the drum and can't dissipate. Running a high-draw load on a coiled reel is how you start a fire.

The rule is simple: always fully unwind a cable reel before powering heavy loads. A heater, a compressor, a wet vac, a large site light — all need the reel fully unwound. Most modern reels have a thermal cutout that trips the circuit if the drum overheats, but thermal cutouts are a last line of defence, not a substitute for correct use.

The Faithfull Open Drum Cable Reel shown here uses an open drum design specifically to aid heat dissipation — one reason open drum reels are preferred for heavy use over enclosed drum designs.

How Many Outlets Do You Actually Need?

Two sockets is rarely enough on site. Four is the minimum for a working setup: one for a tool, one for a charger, one spare, and one in reserve. Six-gang leads with individual switches — like the Daewoo unit above — are popular in workshop settings where you might have a bench grinder, a drill press, a light, and a phone charger all running simultaneously and want to switch individual items without unplugging.

For cable reels specifically, four outlets is the practical standard. Fewer than that and you'll find yourself daisy-chaining extension leads, which is both a trip hazard and a fire risk — never daisy-chain extension reels.

Length: Choosing Between 10m, 15m, 20m, and 25m

Short leads (2m–5m) are for static workstations. Anything less than 10m is rarely worth having on a mobile job. Here's how the lengths break down in practice:

• 10m: Fine for a single room. Limited reach if you're moving between floors or in a large footprint.
• 15m: The sweet spot for most domestic jobs — enough to reach from a ring main socket in one room to the work area in the next, or from ground to first floor.
• 20m–25m: For larger properties, commercial premises, or outdoor work. The Axiom 25m Extension Cable Reel 10A is a solid choice when you need maximum reach. Note the 10A rating on this unit — adequate for standard power tools but check your tool draw before loading it heavily.

Don't buy more length than you need. Every extra metre is dead weight to carry and coil up at the end of the day.

IP Ratings: Indoor vs. Outdoor Use

Standard extension leads are rated for indoor, dry use only. Take a standard 13A gang lead outside in the rain and you've got a live hazard.

For outdoor or damp-area use, you need at minimum IP44 protection (splash proof), and ideally IP54 or higher for exposed outdoor conditions. Check the lead's IP rating before you take it outside. Some cable reels have weatherproof socket covers for outdoor use — but the plug connection to the wall socket still needs to be under cover or in a weatherproof enclosure.

If you're regularly wiring in outdoor sockets, our full extension leads and cable reels range is a good starting point for sourcing the right products for the job.

RCD Protection and Site Safety

BS 7671 requires RCD protection for socket outlets that are likely to supply portable equipment used outdoors. On most domestic jobs, 30mA RCD protection is already built into the consumer unit. On site, you can't always guarantee the circuit feeding your temporary power is RCD-protected.

The practical solution: use an inline RCD adapter plug — it fits between your extension lead and the wall socket and provides 30mA trip protection. It's cheap insurance. Some cable reels come with RCDs built into the drum, which is a cleaner option if you're buying new.

110V vs. 240V: Know the Rules

The HSE recommends 110V CTE (Centre Tapped Earth) distribution for construction sites — the distinctive yellow leads and transformers. At 55V to earth, a shock from 110V CTE equipment is far less likely to be fatal than one from 240V.

The 240V extension leads in this guide are appropriate for:

• Domestic properties during fit-out (low-risk environment, owner occupied)
• Workshops and trade premises with established permanent wiring
• Light commercial work where 110V distribution isn't in use

If you're on a new-build or demolition site, expect 110V to be the rule. Check with the principal contractor before using 240V tools on site.

What to Check Before You Buy

Quick checklist before purchasing:

• ✓ Load rating (13A or 10A?) and wound vs. unwound capacity
• ✓ Thermal cutout fitted (essential on cable reels)
• ✓ Number of outlets (4-gang minimum for site use)
• ✓ Cable length suits the job
• ✓ IP rating matches the environment
• ✓ BS 61242 compliance marked on the label
• ✓ Built-in RCD if RCD protection isn't already at the board

In Stock at APM Electricals, Acton

We stock a full range of extension leads and cable reels at APM Electricals in Acton — 2-gang leads, 4-gang reels, 6-gang switched leads, and heavy-duty 20m and 25m cable drums from Faithfull, SMJ, Axiom, Knightsbridge, and Daewoo. Same-day collection at 24 Western Avenue, Acton, London W3 7TZ. Call us on 020 8702 8080 or order online at apmi.uk.