Every UK three-pin plug contains a small cartridge fuse, and fitting the right one matters. Too high a rating and the fuse may not blow when the appliance lead overheats; too low and it will keep blowing for no good reason. This guide explains what plug fuses do, how 3A, 5A and 13A fuses differ and how to choose and change one safely.
What Does A Plug Fuse Do?
A plug fuse contains a thin wire that melts and breaks the circuit if too much current flows. Its job is to protect the appliance’s flexible lead and the appliance from overheating if there is a fault. It is not designed to protect people from electric shock – that is the job of the RCD protection in your consumer unit – so a plug fuse is never a substitute for a properly installed and tested circuit.
Plug fuses for UK plugs are made to BS 1362, and the plugs themselves to BS 1363. Both standards are normally marked on the product, so check for them when you buy replacements.
3A vs 5A vs 13A: What Is The Difference?
The number is the current the fuse is rated to carry. Most appliance manufacturers now fit either a 3A or a 13A fuse, and 5A fuses are still found in some older equipment.
| Rating | Typical Use |
|---|---|
| 3A | Low-power appliances up to about 700 watts, such as lamps, televisions, computers and chargers |
| 5A | Some older equipment where the manufacturer specifies it |
| 13A | Appliances from about 700 to 3,000 watts, such as kettles, washing machines, microwaves and heaters |
Fuse bodies are often colour coded – 13A fuses are usually brown and 3A fuses red – but colours vary between makers, so always read the rating printed on the fuse itself.
How To Work Out Which Fuse An Appliance Needs
- Check the manufacturer’s instructions first. The instruction book or rating plate often states the fuse to use, and that always takes priority.
- Find the wattage. It is printed on the rating plate on the appliance, the charger or the plug.
- Apply the rule of thumb. Up to about 700 watts, a 3A fuse is usual. From about 700 watts up to 3,000 watts – the most a standard socket should supply – use a 13A fuse.
The rule comes from a simple sum: current (amps) = power (watts) ÷ voltage. On UK mains, 700W works out at roughly 3A and 3,000W at roughly 13A.
How To Change A Plug Fuse Safely
- Switch off at the socket and unplug the appliance. Never open a plug that is still plugged in.
- Open the fuse carrier – on most moulded plugs it is a small drawer on the pin side that you prise out with a flat screwdriver. On rewireable plugs, undo the cover screw.
- Remove the old fuse and fit a new one of the same rating, unless the manufacturer says otherwise.
- Check the fuse is clipped in securely and not loose, close the carrier or cover fully, then plug in and test.
When A Fuse Keeps Blowing
A fuse that blows again straight away is telling you something is wrong. Do not fit a higher rated fuse, and never bridge a fuse with foil or wire. Stop using the appliance and have it checked by the manufacturer, the retailer or a qualified repairer. Also stop using a plug or socket that is hot to the touch, has scorch marks or crackles, and get it looked at by a registered electrician.
Plug Fuses vs Fuses In The Consumer Unit
Plug fuses are the only fuses a householder should normally replace. Circuit breakers, RCDs, RCBOs and rewireable fuses in the consumer unit protect whole circuits. If one of those keeps tripping or blowing, or you want to change anything in the consumer unit, call a registered electrician.
Keep Spares To Hand
Our plug fuses come in packs from 10 to 500, and the Plug Fuse Assortment Pack gives you 10 each of 3A, 5A and 13A – handy for the kitchen drawer, the van or rental properties. Browse the full range in our Fuses and Electrical Installation collections.
Frequently Asked Questions
What Is The Difference Between A 3A And 13A Fuse?
A 3A fuse is for low-power appliances up to about 700 watts, such as lamps and televisions. A 13A fuse is for appliances from about 700 to 3,000 watts, such as kettles and washing machines. Always use the rating the manufacturer specifies.
Are 5A Plug Fuses Still Used?
Most manufacturers now fit 3A or 13A fuses, but 5A fuses are still used in some older equipment. Fit a 5A fuse only where the manufacturer specifies it.
Can I Use A 13A Fuse Instead Of A 3A Fuse?
No. A higher rated fuse may not blow quickly enough to protect a thin appliance lead. Replace a fuse with one of the same rating unless the manufacturer says otherwise.
Why Does My Plug Fuse Keep Blowing?
Repeated blowing usually means a fault in the appliance or its lead. Stop using it and have it checked by the manufacturer or a qualified repairer rather than fitting a bigger fuse.
What Does BS 1362 Mean On A Fuse?
BS 1362 is the British Standard for cartridge fuses used in UK three-pin plugs made to BS 1363. Check for it when buying replacement plug fuses.