You walk into the boiler cupboard of a village cottage you have just bought. There is a grey plastic box on the wall with plug-in switches and a big red main switch to the left. Is it fine, or is it a rewire waiting to happen? Six signs to look for.
1. Rewireable BS 3036 fuses
If the fusebox has removable ceramic or bakelite fuse holders with visible wire inside, that is a rewireable board. Legal to keep, not legal to modify. Anything more than a lamp change should trigger a board replacement. Most Wingham cottages we quote for rewires still had one of these until recently.
2. Single 63A RCD upfront
If everything downstream of the main switch sits behind one RCD, one earth fault trips the whole house. Modern boards use one RCBO per circuit. If the freezer and the boiler and the alarm all live on the same RCD as a sixty-year-old outdoor socket, you have a bad day waiting.
3. No SPD (surge protection device)
Since March 2022, BS 7671:2018 Amdt 2 requires SPDs on most new domestic installs. If the board went in before that and you have a rural overhead supply, you are one summer lightning strike away from replacing the television, the router, the smart meter, the boiler PCB and the oven. An SPD retrofit is a £100 part.
4. Undersized main earth
Look at the earth conductor coming out of the meter cupboard into the consumer unit. If it looks about the same thickness as the meter tails, good. If it looks noticeably thinner, or is not there at all and there is a spike in the corner, you have TT earthing and probably an undersized main earth. On any new board install we upgrade this to 16mm as standard.
5. Warm-to-touch on the outside
Under load the outside of the board should feel room temperature. Warm means loose connections inside, and loose connections mean overheating and eventual failure. On any board where you have added an electric shower or oven since it was installed, get the terminal tightness checked.
6. Plastic board older than 2016
BS 7671 tightened rules on non-combustible enclosures for domestic consumer units in Amendment 3 of the 17th edition (Jan 2016). Plastic boards installed before that are legal to keep, but a plastic board in a Grade II thatched cottage should be a metal-clad on the next replacement cycle regardless of legality.
What to do
If any two of these apply, book an EICR. The report will tell you whether you need a board change now or in the next couple of years, and we can quote the replacement off the same visit.