Replace a rewireable fuse in an old fuse box

Learn to safely isolate power, identify the right fuse wire rating, and rewire a blown fuse in an old consumer unit.

RF-01Get your tools together firstThe power will be off while you work, so get everything ready before you start: a torch, a voltage tester, a small screwdriver, and fuse wire in the right ratings. Old fuse boxes are often in a dark cupboard or under the stairs, so good light matters. Check you know where your consumer unit is and that the main switch moves freely.

1 each · Torch

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1 each · Small flathead screwdriver

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RF-02Find the blown fuseLook along the row of fuse carriers for one with a blackened window or a wire that's visibly snapped or melted. Each carrier is usually marked with its amp rating and sometimes the circuit it feeds, such as 'lighting' or 'cooker'. Note the rating printed on the carrier before you touch anything — you'll need to match it exactly.

RF-03Isolate the supply and prove it's deadSwitch off the main switch on the consumer unit before you pull any fuse carrier out. Use your voltage tester across the carrier's terminals to confirm there's no power, not just the switch position — switches can fail. If you have any doubt at all about whether the unit is dead, stop and call a qualified electrician rather than guess.

1 each · Voltage tester

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RF-04Remove the old wire and fit the correct ratingLoosen the terminal screws and pull out the old wire fragments completely. Fit new fuse wire of the same amp rating as the blown one — never a heavier one, even if it's all you have to hand. Colour coding helps: white is 5A for lighting, blue is 15A for immersion heaters, red or yellow is 30A for sockets and ring mains, green is 45A for cookers and showers. Loop the wire around each terminal two or three times, tighten firmly, and trim the ends close so no loose strands touch the sides of the carrier.

1 each · Fuse wire assortment (5A/15A/30A/45A)

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1 each · Wire cutters

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RF-05Refit the carrier and restore powerPush the fuse carrier firmly back into its slot, making sure it seats properly. Switch the main switch back on and check the circuit you repaired now works, for example by turning on the light or socket that lost power.

RF-06Tidy up and know when to stopDispose of the old wire scraps and wipe down the consumer unit. If the same fuse blows again quickly, don't fit thicker wire to make it stop — that's a fire risk and usually means there's a fault on the circuit that needs finding. Replacing fuse wire like-for-like is basic maintenance and isn't notifiable under Part P of the Building Regulations, but repeated blowing, a damaged fuse box, or any rewiring beyond this should go to a registered electrician.

RULES

KNOW THE RULES

Like-for-like fuse wire replacement is routine maintenance and not notifiable under Part P. Any fault-finding, rewiring, or consumer unit replacement is different and should be done by a registered electrician, with Building Control notification if required.

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