How to use a 50m cable reel: unwind before you load
Updated: 22 October 2026
You already own a 50 m drum and the thermal cut-out tripped last weekend. How to use a cable reel is the unwind, the watt sum, and the point where you stop instead of pressing reset again. The same rules apply to every reel in the [50m cable reel comparison](/hub/sockets-and-extension-leads/50m-cable-reel). The figure on your drum, or in its manual, beats anything written here. If you have not bought yet, start with the [50m cable reel buying guide](/hub/sockets-and-extension-leads/50m-cable-reel/sub/50m-cable-reel-buying-guide). A qualifying purchase can earn a commission at no extra cost to you.
You already own a 50 m drum and the thermal cut-out tripped last weekend. How to use a cable reel is the unwind, the watt sum, and the point where you stop instead of pressing reset again.
You already own a 50 m drum and the thermal cut-out tripped last weekend. How to use a cable reel is the unwind, the watt sum, and the point where you stop instead of pressing reset again. The same rules apply to every reel in the 50m cable reel comparison. The figure on your drum, or in its manual, beats anything written here. If you have not bought yet, start with the 50m cable reel buying guide. A qualifying purchase can earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Wound figure | Reset | Sockets | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  SLx SLx 90071PI | 960 W wound, 3,120 W extended | Red button in the guide | 4 | 8.4 | about £59.99 | View offer |
 Masterplug Masterplug Pro-XT OLU50134SL | Not printed on this listing | Manual reset | 4 shuttered | 8.6 | about £60.99 | View offer | |
| Alternative |  Brennenstuhl Brennenstuhl Standard 1098413 | Not printed on this listing | Push button | 3 | 7.8 | about £69.99 | View offer |
On this page
Unwind the drum before you switch on
A cable left on the drum acts like a coil heater. Electrical Safety First warns that wound cable can overheat, and HSE guidance says only a fully extended lead carries the cable’s full current. Needing ten metres still means you take every turn off the drum before you load it. Run the cable where people will not trip, and keep the sockets out of puddles. Do not cover a loaded drum. Switch the tool off before you unplug, and never pull the plug out by the flex. Disconnect the loads first, then rewind. Dew and an RCD are on the 50m cable reel for the garden page.
Add the watts, then stay inside one 13 A plug
Four sockets still share one BS 1363 plug and one 13 A fuse. The full rating applies only when the cable is fully unwound. Coiled, general guidance often cites about 3 A or 4 A, which is not a measurement of your reel. The SLx guide prints 960 W wound and 3,120 W extended at 240 V. Use another brand’s wound watts only if your own manual prints them. Add everything that will run at once, and stay under the unwound rating only with the cable off the drum. If the cable is still coiled, you are still in the wound zone. Do not plug a second reel into the first, and do not charge an electric vehicle from the drum. Cable codes are on the indoor or outdoor cable reel page.
If the cut-out trips, cool it, then reset once
When the cut-out trips, unplug from the wall, disconnect every load, and let the reel cool. Reset only after the body is cool to the touch. The SLx guide describes a red button, Brennenstuhl a push button, and the Masterplug in this set a manual reset. Unwind any cable still on the drum, check the load against the extended rating, and try once. Do not reset a reel that still feels hot.
Stop instead of resetting again
Hot plastic, scorch marks, a burning smell, or a damaged cable are reasons to replace the lead, not to reset again. A second trip on the same job, after a cool-down and a full unwind, means the reel is wrong for that load or faulty. An RCD that trips at once needs an electrician. Dorset and Wiltshire Fire and Rescue have warned about fires from partly wound extension cables: lay the cable out, and switch off when you finish. A permanent shed supply is fixed wiring, not a drum.
The sequence to follow
Unwind fully, add the watts against the extended rating, and reset only after the reel has cooled. If it trips again, or the plug is hot or smells of burning, stop. A year-round shed supply is an electrician’s job.
Common questions
Do I have to unwind the whole 50 m if I only need 10 m?
For the full 13 A rating, yes. The cable should be fully off the drum. A short job still needs the coil unwound so heat can escape. Leaving most of the length wound is how cut-outs trip on warm days. Electrical Safety First warns that wound cable can overheat. If your manual prints a lower wound figure, that figure applies while any cable remains on the drum.
What load is safe while the cable is still on the drum?
Use the wound figure printed on your reel or in its manual. General guidance often cites about 3 A or 4 A while the cable is coiled. The SLx family guide cites 960 W at 240 V wound and 3,120 W extended. If nothing is printed, assume the wound limit is far below 13 A. Do not borrow another brand’s wound watts for a drum that does not print them.
What do I do when the thermal cut-out trips?
Unplug from the wall, switch off and remove every load, and let the reel cool until the body is cool to the touch. Fully unwind any cable still on the drum, check the combined wattage against the extended rating, then reset once using the control on your reel. The SLx guide uses a red button. Do not reset a reel that still feels hot.
Is it safe to plug a second reel into this one?
No. Electrical Safety First advises one extension device per wall socket. Daisy-chaining reels adds resistance and makes it unclear which cut-out should trip first. Four sockets on one drum already share one 13 A plug. A second reel does not add a second 13 A supply.
Which signs mean I should stop and not reset?
Stop for a burning smell, scorch marks, a cracked or warm plug, a damaged sheath, a second trip after one proper cool-down and full unwind, or an RCD that trips the moment you plug in. Those are reasons to replace the lead or call an electrician. They are not a reason to press reset again.
When do I call an electrician instead of pressing the button again?
Call an electrician for burn marks, a damaged cable, a second trip on the same setup, or any plan for a permanent outdoor supply. Also call if you are unsure the reel matches the load after a full unwind. A domestic drum is not a year-round shed feed and it is not a charger for an electric vehicle.
Related pages
Sources
Sources taken from the research digest. Listings were scored from the stored amazon.co.uk pages. This page did not run a lab test.
- Electrical Safety First — Extension leads and cable reels (retrieved 22.10.2026)
- Electrical Safety First — Overloading sockets (retrieved 22.10.2026)
- Electrical Safety First — Garden (retrieved 22.10.2026)
- BSI — BS EN 61242 cable reels (retrieved 22.10.2026)
- SLx — 30 m and 50 m reel user guide (retrieved 22.10.2026)
- Brennenstuhl — Cable types (retrieved 22.10.2026)
- BEAMA — Extension lead safety checklist (retrieved 22.10.2026)
- HSE — INDG247 Maintaining portable electrical equipment (retrieved 22.10.2026)