Wiring a fused spur socket: a step-by-step guide
In the world of electrical installations, a fused spur socket plays a vital role in providing an extra electrical outlet while ensuring safety. Whether you’re looking to power an additional appliance or create a new circuit, knowing how to install a fused spur socket is a valuable skill. Fused spurs are also commonly known as fused connection units (FCUs).
Let’s dive in and explore the ins and outs of fitting a fused spur socket.
Understanding fused spur sockets
Before we go into installation, it’s important to understand the purpose and function of a fused spur socket. A fused spur is a single electrical outlet with its own designated circuit, typically used for high-voltage and high-power appliances like washing machines, dishwashers or ovens. It features a fuse that protects the circuit from overload or short-circuits, reducing the potential risk of electrical accidents.
They are frequently used to connect outdoor circuitry, such as in a garage, shed or greenhouse, or for a pond pump. You can also have multiple wall sockets running via a single fused spur socket. It provides an extra layer of safety, and if switched, it means all relevant sockets can be temporarily isolated. However, if you’re working on the sockets, do not use that switch to “isolate” them – you should always switch the relevant circuit off at the consumer unit (often known as the fuse box).
As opposed to regular sockets, they are not designed to have a plug inserted into them, so have a blank face. This makes sense as they are only ever meant to have one appliance attached to them.
Fused spur sockets can come with a switch or without. A switched socket should be chosen if the appliance will regularly be used but will also spend a lot of time idle. It might also be useful if it is for seasonal use, for example a heater that is only used in the winter. A fridge might have a fused spur socket with a switch so it can easily be defrosted.
Switchless sockets are useful for appliances that need to be on constantly, especially where accidentally switching off could be damaging or dangerous, such as a medical refrigeration unit. It can still be isolated at the consumer unit, of course.
Safety first
As with any electrical work, you should only attempt this installation if you are competent and understand the principles of electrical safety. If you are replacing one fused spur socket with another, any competent householder should be able to carry out the work. If it’s a brand new installation, however, you should use an electrical contractor to carry it out, as the consequences of errors could be grave. If you’re in any doubt at all, call an electrician.
Materials and tools
To get started, gather the following materials and tools:
- Fused spur socket
- Back box suitable for the type of wall surface you’ll be installing on
- Screws and wall plugs
- Electrical tester
- Screwdriver (suitable for the screws used on your chosen fused spur unit)
- Wire strippers
- Terminal screwdriver
- Wire cutters
Step-by-step installation guide
Note: Before beginning any electrical work, always switch off the relevant circuit at the consumer unit and confirm there is no power flowing to the area you’ll be working on.
1. Prepare the installation area
Select a suitable location for the fused spur socket, ensuring it is easily accessible and in proximity to the intended appliance. Once chosen, mark the position on the wall and turn off the main power supply. If you have to run new cables to the location, make sure you have the appropriate tools to run them through the relevant material or install conduit. Do not attempt this even if you are a competent amateur – you are legally obliged to have such work done by a qualified electrician.
2. Install the back box
Using the appropriate size of back box for your chosen fused spur unit, secure it to the wall using screws and wall plugs. Ensure it is positioned securely and level. You may be able to re-use the old socket box if it’s the same specification.
3. Connect the wiring
Begin by removing the front plate of the fused spur unit. Inside, you’ll find two sets of terminals labelled L, N, and E or ⏚ (Live, Neutral and Earth). One side will be indicated as “supply”, “feed” or “in” (so these wires connect to the mains circuit); the other is marked “load” or “out” (so this connects to the appliance). Strip the end of the existing cable to expose the core wires and connect them to the corresponding terminals: L (brown) to Live, N (blue) to Neutral, and E (green and yellow) to Earth.
4. Secure the wires
After connecting the wires, tighten the terminal screws firmly, ensuring there is no loose wiring. Double-check that the cable grip is secure, preventing any strain on the wires. Do not over-tighten the screws, however, as that can damage the wire. Also make sure that you have not accidentally gripped the plastic insulation, as that will prevent the circuit from completing.
5. Insert the fuse
Insert the correct fuse rating for your fused spur unit (typically 13A, but potentially less depending on the intended appliance). Ensure it is securely in place, as this is your safeguard against electrical damage, or the circuit might simply not work if incorrect.
6. Test the circuit
Before restoring power, use an electrical tester to ensure all connections are secure and the circuit has been correctly installed. If the tester indicates any issues, double-check your connections and seek professional assistance if necessary.
7. Reassemble and test
Once confident in your installation, carefully reassemble the fused spur unit’s front plate. Turn the power back on at the consumer unit, and test the newly installed socket to ensure it provides power to the connected appliance. If the appliance doesn’t work, and you’re sure it is in good working order, switch off the power, undo all the wires and follow Step 3 onwards again. If it’s still not working, call a professional.
Replacing the fuse
If the fuse does blow, you’ll need to isolate the whole property’s electrics at the consumer unit, and access the fuse. This is usually achieved through a pop-out panel on the face plate, which allows you to change the fuse. Slip a screwdriver into the slot, then twist or lever the panel out. Sometimes, the panel has a retaining screw that needs to be undone.
Although fuses do sometimes just burn out, or a power surge can occur that blows it, it’s always worth investigating underlying causes. After all, any power surges should have tripped at the consumer unit, not the fuse. If the fuse of your fused spur socket blows more than once over a short period of time, have your circuitry, consumer unit and appliance checked by an electrician.