Helpful video reference. We use Warren Nash's UK tutorial "How to fit a USB Plug Socket in the UK — Old and New Wiring Colours" as the video reference here. Warren is a UK-based DIY presenter and his walkthrough covers both the old red-black and new brown-blue wiring colour conventions, which is genuinely useful if your house was wired before 2006.
1. Choose the right socket
USB sockets come in several flavours: USB-A only, USB-A plus USB-C, and USB-C only. For most households a dual USB-A and USB-C socket gives the widest compatibility. Check the charging wattage, especially if you want to fast-charge modern phones (look for 20W or higher on the USB-C port).
Before you buy, measure your back box depth. Standard single sockets sit in a 25 mm back box. Most USB combination sockets need 35 mm because the charging module takes up room behind the faceplate. This is the single most common mistake — buying the socket, then finding it will not fold into the existing box.
2. Isolate at the consumer unit
Find the circuit breaker or fuse for the ring or radial circuit supplying that socket and switch it off. In a modern board the circuit will be labelled; in an older board you may need to test each fuse in turn. Confirm the socket is dead with a voltage tester at both the top and bottom outlet before you do anything else.
3. Photograph the existing wiring
Unscrew the faceplate, ease it forward on its cables, and take a clear photo. You want to see which conductor is at which terminal before you disconnect a single wire. This is your reference if anything looks odd when you transfer to the new socket.
4. Check the back box depth
With the old faceplate removed, measure the back box recess. If it is only 25 mm and your new socket needs 35 mm, you have two options: swap the back box for a deeper one (a plaster-depth steel box), or buy a slimline USB socket specifically designed for 25 mm boxes. Both solutions exist; just do not force a deep socket into a shallow box.
5. Transfer the conductors one at a time
Loosen the terminal on the old socket, pull the conductor out, and connect it immediately to the corresponding terminal on the new socket. Brown to L (line), blue to N (neutral), green-yellow to E (earth). Tighten each terminal firmly. Working one conductor at a time avoids any confusion between live and neutral.
Older wiring uses red for live and black for neutral. These are the same conductors — just different colours. Red goes to L, black goes to N.
6. Check the earth
If the back box is plastic, the earth conductor at the socket terminal is sufficient. If the back box is metal, there must also be an earth link from the box to the socket's earth terminal — a short green-yellow conductor. Some sockets come with this; others do not, so buy one if needed. A metal back box without an earth path is a fault waiting to happen.
7. Refit and test
Fold the cables carefully into the back box. No conductor should be kinked sharply or trapped under the edge of the faceplate. Tighten both faceplate screws evenly so the socket sits flush. Restore power at the consumer unit, then test the mains outlet with a plug-in socket tester and the USB ports with a phone or tablet.
When to call us
A like-for-like socket swap is one of the jobs a competent homeowner can handle without calling anyone. The moment it turns into "I want three new USB sockets and none of them are there yet" it becomes a new circuit run, which is Part P notifiable work. That is when you need Richard.
Need sockets changed or added in Sandwich?
Richard fits USB sockets, replaces outdated faceplates and adds new socket positions across east Kent. Small jobs at the £10 per 10-minute rate, larger additions quoted fixed price.
Contact Richard