What Happens When a Fuse Blows
What is a Blown Fuse?
A fuse is a safety device that protects electrical circuits from overcurrent and short circuits. When too much current flows through a fuse, the thin metal ribbon inside the fuse melts, breaking the circuit and preventing damage to the electrical system.
Types of Fuses
There are two main types of fuses:
- Screw-in fuses: These fuses are typically used in older homes and are screwed into a fuse panel.
- Cartridge fuses: These fuses are used in newer homes and are inserted into a fuse block.
Sizing of Fuses
Fuses are sized to match the gauge of the circuit wires. This prevents the circuit wires from drawing more power than they can handle. The correct fuse size for a given circuit wire gauge is:
- 14-gauge or larger: 15-amp fuse
- 12-gauge or larger: 20-amp fuse
- 10-gauge or larger: 30-amp fuse
Common Causes of Blown Fuses
- Overload: An overload occurs when too many lights or appliances are drawing power from the same circuit.
- Short circuit: A short circuit occurs when a hot wire touches a neutral wire or a ground wire, creating a low-resistance path for current to flow.
Other Causes of Blown Fuses
- Ground faults: A ground fault occurs when electrical current flows directly to the ground or a grounded part of the system.
- Arc faults: Arc faults occur when wires and terminals don’t make good contact, causing an electrical arc.
- Circuit issue: A blown fuse or tripped circuit breaker can also be caused by a problem with the circuit itself, such as a surge or a loose connection.
- Damaged outlet or wiring: Faulty wiring or a damaged outlet can create a power surge that can blow a fuse.
How to Identify a Blown Fuse
- Visual inspection: Examine the fuse for a melted metal ribbon or a metallic smear on the inside of the glass tube.
- Multimeter: Use a multimeter to measure the resistance of the fuse. A reading of near 0 indicates a good fuse, while a reading of OL (over-limit) indicates a blown fuse.
How to Replace a Blown Fuse
- Turn off the power at the fuse box.
- Pull the main fuse block out of the panel to disconnect the power.
- Twist the blown fuse out of the socket or use a fuse puller to remove it.
- Screw or push in a new fuse of the same size, amperage, and type.
- Insert the main fuse block into the designated socket and apply firm pressure to fit securely.
- Close the panel door and check if this has restored power to the problem area.
When to Call a Professional
If a fuse blows repeatedly, it is important to call a licensed electrician to identify the underlying issue. This could indicate a problem with the electrical system that requires professional repair.
Tips for Preventing Blown Fuses
- Avoid overloading circuits by plugging too many appliances into the same outlet.
- Use surge protectors to protect sensitive electronics from power surges.
- Inspect electrical cords and outlets regularly for damage.
- Have your electrical system inspected by a licensed electrician every few years.
Additional Information
- What are the benefits of using circuit breakers instead of fuses? Circuit breakers can be reset, while fuses must be replaced. Circuit breakers also provide better protection against overloads and short circuits.
- How can you troubleshoot a blown fuse without calling an electrician? Unplug all appliances and fixtures on the affected circuit. Turn off the power to the fuse box and identify the blown fuse. Replace the blown fuse and turn the power back on. If the fuse blows again, there is likely a problem with the circuit wiring and you should call an electrician.
- What are the different types of fuses and which one is right for my home? Screw-in fuses are used in older homes, while cartridge fuses are used in newer homes. The type of fuse you need depends on the type of fuse panel you have.