WAZIPOINT Engineering Science & Technology: Fuse Rating Selection Chart

Saturday, June 17, 2023

Fuse Rating Selection Chart

Fuse Rating Selection
Fig- A Fuse

When selecting a fuse rating, it's important to consider the current rating of the circuit and the maximum current that the circuit can safely handle. The fuse rating should be chosen to protect the circuit by blowing when the current exceeds safe limits. Here is a general fuse rating selection chart that can serve as a guideline:

Basic Guideline for Fuse Rating Selection Chart

Circuit Current (Amperes)Fuse Rating (Amperes)
0 - 0.50.5
0.5 - 11
1 - 33
3 - 65
6 - 1010
10 - 1515
15 - 2020
20 - 3030
30 - 4040
40 - 5050

Please note that this is just a general reference chart, and you should always consult the specific requirements and guidelines provided by the manufacturer of the equipment or the electrical code applicable to your region. It's also recommended to seek assistance from a qualified electrician or an expert in electrical systems for accurate fuse rating selection in specific applications.

Standard fuse sizes chart

Here is a chart showing standard fuse sizes:
use Size (Diameter x Length)Common Applications
5 x 20 mmSmall electronic devices, appliances
6 x 32 mmIndustrial equipment, power tools
8.5 x 31.5 mmIndustrial equipment, power distribution panels
10 x 38 mmHigh-current industrial applications, motor protection
14 x 51 mmHeavy-duty industrial applications, motor protection
22 x 58 mmHigh-current industrial applications, power distribution
Please note that these are general standard sizes, and there may be variations depending on the region and specific applications. It's always recommended to consult the manufacturer's documentation or electrical code guidelines for accurate fuse size selection.

Amp fuse size chart

Here is a chart showing common ampere (A) fuse sizes:
Fuse Size (Diameter x Length)Maximum Ampere Rating
5 x 20 mmUp to 10A
6 x 32 mmUp to 30A
8.5 x 31.5 mmUp to 63A
10 x 38 mmUp to 125A
14 x 51 mmUp to 200A
22 x 58 mmUp to 400A
These maximum ampere ratings are approximate and can vary depending on the specific fuse model and manufacturer. It's important to consult the manufacturer's documentation or electrical code guidelines to determine the appropriate fuse size and ampere rating for your specific application.

Automotive fuse size chart

Here is a chart showing common automotive fuse sizes:

Fuse Size (Blade Type)Maximum Ampere RatingCommon Applications
ATO / ATCUp to 40ALighting, accessories, smaller circuits
MiniUp to 30ALighting, accessories, smaller circuits
MicroUp to 15ASmall electronics, sensors, control circuits
MaxiUp to 60AHigher power applications, such as cooling fans, power seats
JCASEUp to 60AHigher power applications, such as fuel pumps, high-current accessories
These are common fuse sizes used in automotive applications, but it's important to note that the specific fuse sizes and ratings can vary depending on the vehicle manufacturer and model. Always consult your vehicle's owner's manual or the fuse box diagram to determine the correct fuse size and ampere rating for your specific automotive fuse needs.

What is the Formula to Calculate Fuse Rating?

The formula to calculate the fuse rating is as follows:

Fuse Rating (Amps) = Load Current (Amps) × Overload Factor

The Load Current refers to the normal operating current of the circuit or the equipment you want to protect with the fuse. The Overload Factor is a safety margin that takes into account any expected or potential current surges or inrush currents that may occur during startup or normal operation. In our other episode, we discussed How to Calculate Fuse Ratings for Electrical Appliances.

It's important to note that the Overload Factor can vary depending on the specific application and the industry standards or regulations applicable to your region. The factor is typically specified by the equipment manufacturer or can be determined through engineering analysis.

Additionally, it's essential to select a standard fuse rating that is equal to or greater than the calculated value. Fuse ratings are usually available in standard sizes, so you may need to choose the next higher available rating to ensure proper protection.

Keep in mind, fuse ratings should always be chosen in accordance with applicable codes, standards, and manufacturer recommendations. If you have any doubts or specific requirements, it's recommended to consult with a qualified electrician or an expert in electrical systems.

Can We Use a Modern Circuit Breaker to Instate a Fuse?

Yes, it is possible to use a modern circuit breaker instead of a fuse. In fact, circuit breakers are commonly used as a more convenient and versatile alternative to fuses in modern electrical systems.

Here are some reasons why circuit breakers are preferred over fuses in many applications:

  • Resettable: Unlike fuses, which need to be replaced once they trip, circuit breakers can be reset after they trip, which makes them more convenient to use. This eliminates the need to carry spare fuses and reduces downtime.

  • Overcurrent Protection: Circuit breakers provide not only short-circuit protection but also overcurrent protection. They can detect both overloads and short circuits and can be set to trip at specific current thresholds. This helps prevent damage to the electrical system and equipment.

  • Different Trip Characteristics: Circuit breakers can be designed with different trip characteristics, such as instantaneous or time-delayed tripping, to accommodate specific application requirements. This flexibility is not possible with fuses, which have fixed trip characteristics.

  • Better Coordination: In a complex electrical system with multiple circuits, circuit breakers can be coordinated to ensure that only the faulty circuit is isolated during a fault, while other circuits remain operational. This selective coordination is important for minimizing disruptions and improving safety.

  • Monitoring and Diagnostic Features: Some modern circuit breakers are equipped with additional features, such as built-in sensors, communication capabilities, and diagnostic tools. These features enable remote monitoring, fault diagnosis, and preventive maintenance, enhancing the overall reliability and efficiency of the electrical system.

Despite these advantages, fuses still have some specific applications where they may be preferred, such as in certain industrial settings or for protection against extreme fault conditions. However, in most residential, commercial, and industrial installations, circuit breakers are the more common choice due to their convenience, flexibility, and additional protective features.

Where We Cannot Use a Modern Circuit Breaker Instate of a Fuse?

While circuit breakers are widely used and offer numerous advantages over fuses, there are a few specific scenarios where fuses might still be preferred or required:

  • High-Fault Current Environments: In applications with extremely high fault currents, such as some industrial settings or utility distribution systems, fuses may be preferred due to their ability to quickly interrupt fault currents. Fuses are often rated for higher fault currents than circuit breakers, making them suitable for these high-power applications.

  • Selective Coordination: In certain critical systems, where precise coordination of protective devices is crucial, fuses may be used to achieve selective coordination. Selective coordination ensures that only the faulted circuit is isolated while maintaining power to other circuits. Fuses can provide more precise coordination in some cases, although advanced circuit breaker designs now offer improved coordination capabilities as well.

  • Cost Considerations: In some cases, particularly in low-cost or budget-sensitive applications, fuses may be preferred due to their lower initial cost compared to circuit breakers. Fuses are generally less expensive to purchase and install, making them an economical choice for certain situations.

  • Environmental Considerations: Fuses can be more robust in certain harsh or hazardous environments. For example, in areas with high levels of moisture, dust, or chemicals, fuses might be preferred due to their sealed construction and better resistance to environmental factors.

  • Safety Regulations or Standards: In certain industries or regions, specific safety regulations or standards may require the use of fuses in certain applications. It is important to consult applicable codes and standards to ensure compliance with legal requirements.

While these scenarios represent some situations where fuses may still be preferred, it's worth noting that circuit breakers are suitable for the majority of electrical applications and offer numerous advantages in terms of convenience, flexibility, and added features.

Where to Use 5A & 13A Fuse?

The selection of a 5A or 13A fuse depends on the specific electrical equipment or circuit being protected. Here are some common applications for both:

5A Fuse:

Lighting Circuits: In residential or commercial buildings, lighting circuits typically use 5A fuses. These fuses are designed to protect the wiring and lighting fixtures from excessive current that could lead to overheating or damage.

Small Appliances: Some small household appliances, such as table lamps, radios, or smaller kitchen appliances, may be designed to operate with a 5A fuse. The fuse helps protect the internal wiring and components of these devices.

Electronics: Certain electronic devices or low-power equipment, such as televisions, audio systems, or computer peripherals, may incorporate a 5A fuse for overcurrent protection.

13A Fuse:

Power Outlets and Sockets: The most common use of a 13A fuse is in power outlets and sockets. These fuses protect the wiring in the electrical system and prevent excessive current from flowing through devices connected to the outlet. It is the standard fuse rating for general-purpose power outlets in residential and commercial buildings.

Kitchen Appliances: Many kitchen appliances that draw higher power, such as electric kettles, toasters, microwave ovens, or electric cookers, typically require a 13A fuse. This higher rating allows for the higher current demands of these appliances.

High-Power Tools: Power tools, such as drills, saws, or high-power garden equipment, may require a 13A fuse to handle the larger electrical currents they draw during operation.

It is important to note that these are general guidelines, and the appropriate fuse rating may vary depending on the specific equipment, its power requirements, and any manufacturer recommendations. Always refer to the manufacturer's instructions or consult a qualified electrician for proper fuse selection and installation.

Does Fuse Rating Depend on Frequency?

No, the fuse rating does not depend on the frequency of the electrical circuit. The fuse rating is primarily determined by the current-carrying capacity of the circuit and the maximum current that the circuit can safely handle.

Fuses are designed to protect circuits from the excessive current by blowing and breaking the circuit when the current exceeds the fuse's rated value. This is independent of the frequency of the electrical signal flowing through the circuit.

However, it's worth noting that in some cases, the heating effects of high-frequency currents may have an impact on the overall temperature rise in the circuit. This can potentially affect the fuse's performance or the circuit's overall current-carrying capacity. In such cases, it's advisable to consult the manufacturer's recommendations or consult with an expert in electrical systems to ensure proper fuse selection for specific high-frequency applications.

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