What is a Fuse - Function, Selection, and Troubleshooting Tips (2024)

What is a Fuse?

A fuse is an electrical safety device that protects electrical circuits and electronics devices from damage caused by excessive current. It does so by melting and breaking the circuit when the current surpasses the safe limits. Fuses are available in various types and ratings, making choosing the appropriate fuse for the specific application crucial. In addition, proper electrical engineering selection and maintenance of fuses can help prevent electrical fires and ensure the safety and longevity of your electrical systems.

What is a Fuse - Function, Selection, and Troubleshooting Tips (1)

Various fuses are available, each designed for specific applications and environments. Some common fuse types include cartridge fuses, which are cylindrical and used in electrical panels or appliances; automotive fuses, typically found in vehicles' electrical systems; and high voltage fuses, which protect electrical equipment in power transmission and distribution systems.

Fuse ratings are essential when selecting a fuse for a particular application. The rating indicates the maximum current the fuse can safely carry before thefuse blows. Choosing a fuse with a suitable rating for the electrical device or circuit it is meant to protect is crucial. Overrating or underrating a fuse can lead to inadequate protection or nuisance tripping, respectively.

A blown fuse is a common indicator of an issue within an electrical system, such as an overload or a short circuit. Symptoms of a blown fuse can include loss of power to a specific device, circuit, or area of the building. First, replace a blown fuse, turn off the power to the circuit, remove the faulty fuse, and install a new fuse with the same rating. It is essential to identify and address the cause of the blown fuse to prevent further issues.

Fuse boxes and circuit breakers are protective devices that safeguard electrical systems but function differently. A fuse box contains fuses that melt and break the circuit when excessive current flows through them, while a circuit breaker is a reusable switch that trips and interrupts the flow of current when it detects an overload or short circuit. Circuit breakers are generally more convenient and safer as they can be reset, unlike fuses that need replacement after blow.

To identify a fuse in an electrical panel, look for small, cylindrical or rectangular devices with metal caps on either end or a transparent window that reveals the element. Fuses are typically labelled with their ratings, making it easier to select the appropriate replacement if needed.

How is a fuse different from a circuit breaker?

A fuse and a circuit breaker are electrical safety devices designed to protect electrical circuits and devices from damage due to excessive current caused by overloads or short circuits. However, they function differently and have distinct features that set them apart:

  • Functioning mechanism: A fuse consists of a metal wire or strip that melts and breaks the circuit when too much current flows through it. Once it has blown, it must be replaced with a new fuse. On the other hand, a circuit breaker is an electromechanical switch that trips and interrupts the flow of current when it detects an overload or short circuit. Unlike a fuse, a circuit breaker can be reset after it trips, restoring the electrical circuit without needing replacement.
  • Reusability: Fuses are single-use devices that must be replaced after a blow. However, circuit breakers are reusable and can be reset after tripping, making them more convenient and cost-effective in the long run.
  • Responsiveness: Circuit breakers generally trip faster than fuses in response to overloads or short circuits. This quicker response can be advantageous when rapid protection is crucial to minimize damage to electrical components.
  • Selectivity: Circuit breakers offer a wider range of current ratings and can provide more precise protection for various electrical loads. Some advanced circuit breakers also have adjustable settings, allowing for better customization of the protection level.
  • Cost: Fuses are generally less expensive than circuit breakers upfront. However, since circuit breakers can be reset and reused, they may be more cost-effective, especially when electrical faults occur frequently.
  • Size and form factor: Fuses are typically smaller and available in various shapes and sizes, such as cylindrical or blade-type designs. Circuit breakers are generally larger and housed in a box or panel, often with a switch-like appearance.
  • Indicator: Some circuit breakers have a visual indicator, such as a trip flag, to show when they have tripped. On the other hand, fuses may require inspection or testing to determine if they are blown, although some designs have a transparent window to check the element visually.

What is a fuse?

While both fuses and circuit breakers serve the same purpose of protecting electrical circuits from excessive current, they differ in their functioning mechanisms, reusability, responsiveness, selectivity, cost, size, and visual indication. Therefore, choosing between a fuse and a circuit breaker depends on the specific application, budget, and preferences for convenience and maintenance.

What is a Fuse - Function, Selection, and Troubleshooting Tips (2024)

FAQs

What is a fuse and its function? ›

An electric fuse is a safety device which limits the current flowing in an electric circuit. When the current in the circuit increased beyond the limit, fuse burns and it saves different electrical appliances.

What is fuse selection? ›

Properly selected fuses prevent accidents by breaking abnormal currents when they flow through electric circuits. Improper selection, however, can result in nuisance operations, continued flow of abnormal currents, generation of smoke and/or fire, and other dangers.

How to troubleshoot a fuse? ›

Remove the fuse from its holder. In some cases you may need a small screwdriver to unscrew the fuse holder cap. Look at the fuse wire. If there is a visible gap in the wire or a dark or metallic smear inside the glass then the fuse is blown and needs to be replaced.

What is the rule for choosing a fuse? ›

As a general rule of thumb, it is important to pick an amperage rating for the fuse slightly larger than the value of the steady state current,” Ford said. “It is also important to verify that the fuses being considered meet the voltage requirements of the application.

What is the primary function of a fuse? ›

The fuse breaks the circuit if a fault in an appliance causes too much current to flow. This protects the wiring and the appliance if something goes wrong. The fuse contains a piece of wire that melts easily. If the current going through the fuse is too great, the wire heats up until it melts and breaks the circuit.

How does a fuse work in short answer? ›

A fuse consists of a piece of wire made of a metal or an alloy of an appropriate melting point, for example, aluminum, copper, iron, lead etc. If a current larger than the specified value flows through the circuit, the temperature of the fuse wire increases. This melts the fuse wire and breaks the circuit.

What typically causes a fuse to fail? ›

The most common reason for a blown electrical fuse is an overwhelmed circuit. A fuse can blow when a high-wattage appliance or too many appliances are plugged in and run on a single circuit, drawing more power than the circuit's capacity.

How to select fuse current? ›

First, you will need to determine the maximum fuse rating in amperages by applying this formula for calculation: P (Watts) ÷ V (Voltage) = I (Amps). Next, you will need to calculate the minimum fuse rating or amperage by multiplying that total (the maximum amperage rating) by 125%.

What are two ways to test a fuse? ›

Multimeters measure AC and DC voltage, electrical resistance, and the flow of current. For testing a fuse, you can either use it to measure the continuity (which tests if the circuit is complete) or the ohms (which tests resistance).

What is the rule of thumb for fuse selection? ›

The basic rule of thumb is that the voltage rating of the fuse must always higher than the voltage rating of the circuit that it is protecting. For example, if the circuit voltage is 24V, then the fuse voltage rating must be higher than 24V (yes… it can be 250V… just so long as it's higher than the circuit voltage).

What happens if you use a 13 amp fuse instead of a 5? ›

The 5A fuse protects the cable and/or the device which is connected via the plug to the mains. If you replace it with a 13A fuse, it may work if cable and device are in OK condition. But the protection effect is gone. If the device or the cable are defect or short circuited or similar, there may be a fire hazard.

What is the 80 rule for fuses? ›

The 80% rule says that no individual load shall exceed 80% of the branch circuit current rating. That reduces the probability of nuisance circuit breaker tripping.

What is a fuse in simple terms? ›

A fuse is a safety device in an electric plug or circuit. It contains a piece of wire which melts when there is a fault so that the flow of electricity stops. The fuse blew as he pressed the button to start the motor.

How do fuses differ from circuit breakers? ›

While a fuse prevents devices and homes against power overloads only, circuit breakers protect homes and devices against power overloads and short-circuiting.

What is the main purpose of using a fuse in an electric circuit? ›

PURPOSE OF FUSE IN HOUSEHOLD CIRCUIT: It safeguards the circuit and the appliances connected in the circuit from being damaged if the current in the circuit exceeds the specified value due to voltage fluctuation or short-circuiting. Q. How is a fuse put in an electric circuit?

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