How to Choose The Right Circuit Breaker

Circuit breakers play a crucial role in safety precautions. They regulate the quantity of electricity that passes through the electrical power supply system of a place. A properly functioning circuit breaker will identify and switch off the electrical supply if your place experiences an electric overload or short circuit. This will safeguard your cables and electrical equipment until the issue is solved and the power is restored. 


A spring is wrapped over a little bit of solder within each circuit breaker. Each circuit breaker is connected to a wire that travels throughout your home. The solder conducts the energy that runs through your home. The solder melts when the associated wiring is at risk of overheating, causing the spring to stretch through the solder, pulling the switch off and shutting down a particular circuit. It is possible to reset the alloy once it has cooled down.


In order for a circuit breaker to perform successfully, you must fit the circuit breaker meet to your specific demands. After reading the following straightforward explanations, you’ll be equipped to select the proper circuit breaker for your property.

Voltage Rating

vacuum Circuit breaker

There are three voltage capacities for circuit breakers. Each one is designed to hold a specified amount of power.

Interruption Medium


Interruption medium is basically the fluid that is used to break the passing of electric current in the circuit breaker. The fluid is usually oil, vacuum, gas or maybe no material at all.


Oil circuit breakers were widely used in utility industries in the past. However, owing to the popularity of the vacuum circuit breakers, and the ease of maintenance, vacuum circuit breakers are more widely used now.



Circuit breakers with a capacity of up to 600 amps can be used at frequencies ranging from 50 Hz to 120 Hz. The high voltage vacuum circuit breaker will have to cut power if the frequency is higher than 120 Hz. Eddy currents and iron losses generate more heating within the thermal trip components during higher frequency applications, necessitating the breaker to be derated. The overall amount of duration is determined by ampere rating, frame size, and current frequency. As a general rule, the higher the ampere rating is in the given frame size, the more derating is required.


All breakers with a greater rate than 600 amps have a transformer-heated bimetal and are only appropriate for 60 Hz AC. Special calibration is commonly offered for 50 Hz AC minimum applications. Pre-calibrated breakers are available for 50 Hz and 60 Hz applications. The frequency of a diesel generator project will be either 50 Hz or 60 Hz. Before beginning a 50 Hz project, verify with an electrical contractor to ensure that all necessary calibration methods are in place.

Continuous Current Rating

current chopping

An industrial circuit breaker is rated in amperes at a specified ambient temperature when it comes to the continuous current rating. The continuous current that the breaker carries at the room temperature where it was calibrated is specified by this ampere rating. Manufacturers of circuit breakers should calibrate their standard breakers at 104° F as a basic rule.


The kind of load and duty cycle determine the ampere rating for every conventional application. The National Electrical Code (NEC) governs ampere rating and is the principal information source on load cycles in the electrical contracting sector. Electrical and feeder circuits, for example, typically require a circuit breaker rated for the wire current carrying capacity. Consult NEC table 210.24 for varied standard breaker current ratings for various size conductors and acceptable loads.

Trip Curve

trip curve

Simply described, a trip curve is a graphical representation of a circuit protection device’s intended behavior. Manufacturers of circuit safety devices give them to help customers choose devices that provide adequate equipment safety and efficiency while reducing nuisance tripping.


Circuit breakers must trip quickly enough to prevent equipment or wire failure, but not so quickly that they cause false or unnecessary trips.  Circuit breakers must be sized adequately to account for inrush current to prevent nuisance trips. The transitory current transient that happens quickly (within half an AC cycle) following contact closure is defined by NEMA as instantaneous peak inrush.


When a machine, such as a clothes washer or vacuum cleaner, starts up, inrush current causes the lights in a house to decrease.

Maximum Interrupting Capacity

MCB circuit breaker

The interrupting rating is the maximum amount of fault current that the breaker Control Panel can handle. Circuit breakers have the ability to interrupt without triggering power failure. At any given time, the maximum amount of fault current delivered by a system can be estimated. 

When selecting the right indoor circuit breaker, one unbreakable rule to remember is that the breaker’s interrupting capacity must be equal to or more than the quantity of fault current that can be supplied at the point in the system where the breaker is installed. The breaker will be damaged if the necessary quantity of interrupting capacity is not applied.

Atypical Operating Conditions

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It’s critical to consider the end user’s location while choosing a medium voltage vacuum circuit breaker. Each breaker is unique, and some are better adapted to harsher situations than others. Consider the following possibilities when deciding which circuit breaker to use:

Shock Probability

A particular anti-shock device should be fitted if a circuit breaker is intended to be installed in a location where there is a serious risk of mechanical shock. Under normal shock situations, anti-shock devices consist of an inertia counterweight over the center pole that keeps the trip bar fastened. This weight should be installed so that it does not interfere with the operation of heat or magnetic trip units in overloading or short circuit situations.

High Temperature

Standard circuit breakers must be derated or recalibrated to the environment if used in temperatures above 104° F. All breakers were calibrated for 77 degrees Fahrenheit for several years, which meant that any breakers that exceeded that temperature had to be derated. Most enclosures were around 104° F in reality, and a universal special breaker was utilized in these instances. In the mid-1960s, industry standards were updated to require that all standard breakers be calibrated for a temperature of 104 degrees Fahrenheit.


A draw out breaker must be derated for current carrying capacity, polarity, and interrupting capacity in regions where the elevation is greater than 6,000 feet. Thinner air at higher altitudes does not transfer heat away from current-carrying components and thicker air at lower altitudes. Aside from overheating, the thinner air inhibits the insulating charge from forming quickly enough to tolerate the same voltage levels as at normal pressure.

Most commonly used generators and other power-producing equipment can be harmed by altitude difficulties. Before making a purchase, it is advisable to consult with a power generation expert.

Moisture and Corrosion

A withdrawable circuit breaker should be treated with a particular moisture treatment in locations where moisture is present all of the time. This treatment protects the device from mold and fungus, which can erode it. The use of space heaters in the enclosure is the ideal solution in environments where excessive humidity is frequent. Breakers should be relocated from corrosive locations if at all possible. If this isn’t possible, corrosion-resistant breakers can be purchased separately.

Resting Position

Circuit breakers can be installed vertically or horizontally in most cases without impacting the triggering mechanisms or disrupting capacity. It is critical to put the breaker in an enclosure on a platform that sways somewhat with the air in high-wind zones. When a circuit breaker is affixed to an inflexible surface and exposed to heavy winds, the circuit may be disrupted.

Number of Poles


The number of poles refers to the number of entirely different circuits that can be protected by a circuit breaker at the same time. Single-pole circuit breakers can be developed into multi-unit or multi-pole assemblies, or single-pole circuit breakers can be formed into multi-unit or multi-pole assemblies.


A single-pole circuit breaker has three wire terminals for 20 amp 120VAC circuits. A 240VAC circuit with two hot wires can withstand up to 60 amps. Each wire requires its own breaker, but if one is turned on, the other must be turned off as well, or one wire will continue to carry current. A twin pole breaker does this function. A double pole breaker has twice the diameter of a single-pole breaker and has 4 terminals.


A three-phase electrical supply is used in industries, workshops, and office properties. Three hot wires give 480VAC to three-pole circuit breakers. As a result, the breaker requires three distinct switches that will cooperate when necessary. It’s basically three single-pole breakers tethered together. It’s three times the length of a single-pole breaker, with connectors for five wires.

Application of Circuit Breakers

Industrial Circuit Breaker Application

Circuit breakers are automatic switches designed to safeguard electrical circuits from harm. They accomplish this by actively halting current flow if they identify an overload, a short circuit, or another malfunctioning situation. Circuit breakers merely require a manual or automatic resetting to return to service after a circuit breaker has been engaged.

Circuit breakers are essential for an industrial power network’s longevity. These breakers, as part of the power control system apparatus, must be maintained in separate enclosures from other equipment.

The best strategy to ensure nominal operation and worker safety are to carefully design a layout for the complete variety of parts, with high-power and low-power parts separated. It’s critical to consider any electromagnetic field produced by a component that could interfere with another. This is especially true with high-voltage circuit breakers, which can cause low-voltage electronic components to malfunction.

House Circuit Breaker Application

Home circuit breakers are designed to safeguard a home’s wiring from overheating as a result of a rise in temperature caused by high current flow in a wire that isn’t designed for it. Too many appliances functioning from the same wire or output at the same time causes high current flow in the wires at home. The home circuit breaker, by tripping, effectively works as a safety measure to prevent any more damage to the appliances, or worse, the entire house.

Things To Consider While Selecting A Location of Installing The Circuit Breaker


Evaluate the wire size indicated on the cable that will be attached to the circuit breaker to determine the optimum size circuit breaker for your specific domestic purposes. There are two metrics listed: The first number represents the wire gauge, followed by a dash, and a second number indicating the number of wires within the cable. After you’ve determined the wire gauge, use the chart below to select the appropriate circuit breaker:

A 40-amp circuit breaker is made of 8-gauge wire.
A 30-amp circuit breaker with 10-gauge wire
A 20-amp circuit breaker with 12-gauge wire
A 15-amp circuit breaker with 14-gauge wire

Ambient Temperature

A temperature of more than 104°F necessitates calibration. The functioning of the circuit breaker might be affected by high ambient temperatures. Almost all domestic circuit breakers use this calibration because most enclosures are around 104°F.

If the temperature is below or over 104°F, you may need to calibrate upward or downward.


Different circuit breakers are appropriate at various different altitudes. High elevations exceeding 6000 feet, for example, have thinner air that does not transport away the heat from current-carrying components. This necessitates calibrating the circuit breaker for voltage, carrying capacity, and interrupting capability.

The build-up of electrical charge that is able to withstand voltage levels is prevented by thinner air. Altitude can also reduce the efficiency of power-producing equipment. Before choosing circuit breakers for high attitudes, consult a power generation professional.

Moisture And Corrosion

For humid situations, a special moisture solution for the circuit breakers is advised. Fungus and mold, which are renowned for ruining systems, can be helped by treating circuit breakers. Space heaters are frequently utilized in enclosures in high-humidity situations.

Corrosion wreaks havoc on circuit breaker components, resulting in malfunctioning systems. If they must be utilized in corrosive environments, specialized corrosion-resistant versions should be employed.

High Shock Probability

Electrical shocks are a common occurrence in several workplaces. Anti-shock mechanisms should be put in this scenario to avoid any disasters.

Anti-shock devices are made up of inertia counterweights that are attached to the poles that support the trip bar. The thermal or magnetic trip units, on the other hand, should not be affected by this weight.

Maintenance Difficulty

When selecting a circuit breaker, it’s also important to examine the circuit breaker’s maintenance needs. Circuit breakers with low maintenance requirements should be considered. If you need to perform circuit breaker maintenance, it should be simple and inexpensive.

Because the closed device is protected from dust, mildew, moisture, and filth, molded circuit breakers are dependable. In comparison to open models, enclosed models require less upkeep. To avoid overheating and breakage, some circuit breakers must be cleaned on a regular basis; as a result, the breakers should be able to open freely for maintenance.


Indoor circuit breakers are intended for use in secure enclosures. Buildings should have these breakers installed to protect them from the elements. Medium-voltage circuit breakers are controlled by metal-clad switchgear enclosures.

Outdoor circuit breakers, on the other hand, do not need any shielding or roofing. In comparison to their indoor counterparts, they have more robust enclosure structures. They are employed in more complicated power systems since they are not impacted by wear and tear.

Every electrical circuit requires circuit breakers. Always exercise caution when working with electricity and remember to turn off the breaker before beginning any electrical work. Also, make sure you’re using the right sort of breaker for the circuit.

Table of Contents


We can all agree that circuit breakers are an integral aspect of any electrical system and that their appropriate use is critical. An engineer must understand the fundamentals and functioning concepts of circuit breakers, as well as the proper choice of circuit breakers based on the application.


Finally, even if you’re a do-it-yourselfer, you should leave electrical work to the professionals. Your circuit breaker box isn’t as straightforward as the rest of your household appliances. If you try to meddle with the multiple cables, breakers, and voltage offerings in your panel, you could end up causing serious damage, especially if you’re trying to find a solution for often tripping breakers. Simply said, you should get your circuit breaker box examined by a professional if you suspect a problem and get circuit breakers from reliable circuit breaker brands.

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