How To: Change Fuse in Fusebox

Many modern homes come with a fusebox (or “consumer unit”) that can be repaired at the flick of a switch – but if you live in an older property with a traditional fusebox, the process is a little more complicated. Knowing how to change fuse in a fusebox is useful, but if you are at all uncertain about carrying out the work (or if you need a new fusebox), contact a trained electrician.

Safety Measures

When carrying out any electrical work in the home – however minor – it’s important to exercise caution, as electricity can be very dangerous and can cause shocks or fires that can be fatal.

Some Precautions:

1. Some electrical work must be compliant with Part P building control and carried out in accordance with BS7671 wiring regulations and may require a qualified electrician.
2. Wear rubber-soled shoes.
3. Ensure the floor under the fusebox is dry.
4. To avoid another overload, always replace the fuse with one that has the same amperage.
5. In the case of a short circuit it’s best to leave the work to a trained expert as these can be especially dangerous.

What You’ll Need:

1. An insulated screwdriver or an electrician’s screwdriver to avoid getting a shock through the metal of the driver itself. They are plastic coated and valid up to 1000v.
2. A tray or something else to keep hold of any screws.
3. A cartridge fuse tester, if you are replacing a cartridge fuse.
4. A replacement fusewire, if you are replacing this (your local hardware store can advise on finding an exact match).

How Do I Change A Fuse?

1.   Unplug Everything

To change fuse in fusebox, it’s first important to identify the source of the outage as this will also help you to find which fuse is the issue.

To test this:

• Flip the light switches in each room to see which one has lost power.
• Keeping the lights turned off in the affected areas, unplug some of the appliances in these rooms. Bear in mind that if you keep everything turned on and then replace the new fuse, you risk another blow-out or tripping the electrical panel.

2.   Turn Off The Power

The next step is especially important to stay safe.  To switch off the main source of power to the fusebox. You can do this via your electrical panel.

3.   Locate The Fusebox

It’s important to know where your fusebox is in the home in case of an event such as a blown fuse. Older homes tend to have a fusebox, while those built after 1965 or remodelled and rewired properties will have a circuit breaker box. These both do the same thing and can often be found in utility rooms, cellars or the garage.

4.   Open The Fusebox

Remove the fusebox cover by unscrewing the corners with a screwdriver, or remove the plastic cover.

5.   Find The Broken Fuse

Next, you need to identify which fuse has blown by looking for a fuse where the glass covering is discoloured, foggy – or where the metal filament has melted.

6.   Check For Current

1. If you haven’t already done so, switch off the damaged fuse and set your multimeter to “Volt AC”.
2.  Rest one pin on the terminal screw of the faulty fuse and the other on the ground screw situated opposite in a bar or row to one side of the box.
3.  The reading should show no voltage.  If it doesn’t, stop work immediately and call an electrician for support.

7.   Remove The Faulty Fuse

To do this, you’ll either need to pull or lever it from the socket or unscrew it.  The fuse will stay connected to either one or two wires, so detach these by loosening the terminal screws, taking note of which colour wire attached to which end of the fuse for reference later.

8.   Replace The Fuse

Unscrew the broken fuse and screw the new one into the socket. Depending on the type of fuse, you may need to do one of the following:

Replace The Fuse Wire

1. Set the new Fuse to the “off” position.
2. Insert each of the individual wires one by one into the terminal of the new fuse, tightening the retaining screws with your screwdriver. 
3. Push the new fuse back into its socket.
4. If it has them, tighten any retaining screws before flipping the lever switch back on.

Replace A Cartridge Fuse

1. Switch off the main fuse in the fusebox.
2. Carefully remove one of the cartridges (there may be a screw in the cartridge carriers that you can remove).
3. Test the fuse in the cartridge fuse tester.
4. If it works, put it back in the cartridge, replace it in the fusebox and continue to the next one.
5. Once you’ve identified the blown fuse, replace this with a new one, making sure the new fuse has the same amp rating as per the fuse carrier requirements.
6. Turn on the main switch again.

For Circuit Breakers

If you have a new-style circuit breaker, turn off all appliances on the affected circuit and flip the switch to turn the miniature circuit breaker back on before checking the circuit.

9.   Check The Circuit

1. Look at all the items on the circuit to make sure they are operating correctly.
2. Check for signs of breakdowns or damage to appliances, lights and fittings.
3. If you find any damage, do not plug this item back in, as the fuse may blow again.
4. If you are unsure which appliance is faulty, you may have to sacrifice a fuse to find out by turning on your items individually until the fuse blows again (the item you turn on just before the fuse blows will be the likely source of the problem.)
5. Make sure you are not overloading any sockets (overloaded extension cords are a common reason for this).
6. If the blown fuse has affected the entire power circuit, turn off and unplug every device that uses the circuit. For lighting circuits, turn off all the light switches, so that when you fix the circuit and switch the mains back on the fuse will not blow again.

10.   Reconnect The Supply

Turn the fusebox back on, replacing the box cover and re-inserting the screws and tightening them.

11.    Test Everything

Once you’ve finished, turn the main power back on to ensure the new circuit is working. Switch on the lights and start plugging in essential appliances, taking care not to overload the circuit that was the original source of the problem.

When Might I Need Help?

If the fuse blows again (or blows repeatedly), it may be time to contact a professional, as this suggests a larger electrical issue that needs addressing. They can also install a new fusebox if your existing one needs replacing. Contact your local electrician Wigan, electrician Southport or any of our other locations more details.