In almost every home, business, or factory is a critical element of safety that most people take for granted; the Electrical Panel contains our emotions (both the good and the bad) as well as a few switches that have probably never been utilized until something has happened like a surge or someone tripped over their vacuum cleaner. This happens to be the same location where an appliance becomes “popped” and results in the entire room including all electrical items losing power — this switch is known as Circuit Breakers. In fact, even though they may not get a lot of use on a day-to-day basis, Circuit Breakers are the most important piece of equipment in your electrical system.
In conclusion, circuit breakers prevent excessive amounts of electricity from being conveyed by cutting off the supply of electrical energy if there is an overcurrent because of excessive load or if a user has created a situation in which an electrical circuit is defective. The mechanisms used in circuit breakers allow users to trip out excessive energy without having to purchase new fuses; however, once a circuit breaker has been tripped it must be reset before being reused. The types of ratings for circuit breakers are: the amount of current the breaker can handle, the voltage ratings, the rating for interrupting, the rated number of poles in a circuit breaker and the rating for tripping characteristics.
What exactly is a circuit breaker?
The Circuit Breaker is an electrical component that connects to both the electrical distribution system (Power Supply) and as well as the distribution of electricity through the electrical wiring to electrical devices throughout the building (Lights, Outlets). The main functions of the Circuit Breaker includes monitoring the electrical system and disconnecting the electrical supply to that electrical circuit when it detects an unsafe amount of current. The Circuit Breaker also provides protection to the surrounding wire from overheating, protects electrical devices connected to the circuit from becoming damaged, and finally protects individuals who may come into contact with the circuit from being shocked or burned.
One way to visualize the Circuit Breaker is to think of how a security guard would operate in front of a nightclub. During a normal night, the security guard would “let” normal, everyday guests through without any issues. If, however, there were to be an unexpected crowd of people who surged into the doorway (an unwanted surge in current), or if someone attempted to force their way into the nightclub (in the case of a short), the security guard would immediately slam the door shut. The guard continues to be available to perform his/her function of keeping the guests out of harm’s way (the whole purpose of using a Circuit Breaker versus using a fuse). Once the situation has stabilized, the security guard can allow another guest back into the club just as the Circuit Breaker can be reset to allow the electrical supply to flow again.
The Circuit Breaker has been around for a very long time. Thomas Edison patented his first Automatic Circuit Interrupting System in 1879 to use as part of the lighting systems he developed. The first Knife Blade and Cartridge types began appearing around 1900. In 1924, Hugo Stotz designed and built the first true Thermal-Magnetic Miniature Circuit Breaker combining both trip mechanisms into one small device. The design from 1924 is still being used today and the Miniature Circuit Breakers available for purchase today are using exactly the same two functions as the original Circuit Breakers.
How does a circuit breaker work?
The two sensors detect overcurrent and instantaneous short circuit conditions, respectively. The thermal sensor detects excessive current through temperature-sensitive devices (thermistors) which become unusable when they exceed their allowable rated temperature. The magnetic sensor detects the presence of a large amount of current (like that found in short circuits). In addition to detecting overcurrent conditions, the thermal sensor protects against equipment damage caused by excessive heating due to prolonged overload situations, while the magnetic sensor protects against equipment damage due to rapidly rising current levels in short-circuit conditions.
The thermal-magnetic breaker design is the most widely used. The trip mechanism on many electrical switches operates on the same principle as this breaker design; when the current exceeds a certain level, it triggers an electronic circuit that opens the switch. Some electronic trip mechanisms will allow the user to manually open or close the circuit by using a toggle switch. In contrast, most electrical breakers use mechanical trip mechanisms that open and close the circuit automatically.
| Fault type | What happens | Detection element | Время реакции |
|---|---|---|---|
| Overload (e.g., too many appliances on one circuit) | Current modestly exceeds rating; heat builds up over seconds or minutes | Bimetallic strip that bends as it heats, releasing the latch | Seconds to minutes — slow and heat-dependent, which is deliberate |
| Short circuit (hot wire touches neutral or ground) | Current spikes to hundreds or thousands of amps almost instantly | Electromagnetic solenoid that yanks the latch open | One half-cycle or less (about 8-16 milliseconds) |
The delay in the thermal characteristic of a breaker is a desirable feature, not a flaw. When a motor starts, it will momentarily pull a current several times greater than its normal operating current; therefore, the bimetallic strip must have been subjected to extended periods of heat before it will trip (open the contacts) so that the current surging at start-up doesn’t cause nuisance tripping. However, the electromagnetic force generated by a dead short is so strong that it will cause a breaker to trip within one AC cycle before the wiring can wire can overheat and/or cause a fire.
Opening the contacts of a breaker is only one part of stopping heavy current flow. When a circuit breaker interrupts heavy current flow, the electrical arcing process will ionize the air between the contacts as they open and create an electrical arc that will continue to conduct unless interrupted. This is the reason breakers are designed with arc control so they can stretch, cool and separate electrical arcs from the points of interruption. Circuit breakers are rated with an interrupting rating (measured in kA) that help to determine the maximum fault current that can be safely interrupted by the circuit breaker. A residential circuit breaker typically has an interrupting rating of 5-10 kA whereas an industrial molded case circuit breaker will have a rating of 25-100 kA. Selecting a circuit breaker with a lower interrupting rating than the available fault current is a serious safety violation and will not clear faults, but could instead explode.
Trip curves: what the B, C, and D letters mean
Miniature Circuit Breakers (MCBs) have a letter in front of the current rating (B16,B32 etc.) to indicate the trip curve. The trip curve determines how much overload (instant trip) the magnetic (instant trip) will tolerate before it makes contact. Using the correct trip curve is important when selecting the correct MCB for the load because:
| Кривая | Instant trip threshold | Typical loads | Примечания |
|---|---|---|---|
| Тип B | 3-5 × rated current | Resistive loads: lighting, heaters, sockets in residential settings | Most sensitive; not for motors or transformers |
| Тип C | 5-10 × rated current | Small motors, fluorescent and LED drivers, general commercial loads | The most common general-purpose choice |
| Тип D | 10-20 × rated current | Transformers, large motors, welding equipment, high-inrush machinery | Tolerates large starting surges without nuisance trips |
| Type K / Z | Specialized | Semiconductor protection (Z), motor protection (K) | Niche industrial applications |
Using the correct trip curve for a load can be the deciding factor in whether you will receive usable protection when using an MCB or be frustrated at the number of times you are shut off by an MCB. If a large motor circuit uses a Type B MCB, it may continuously trip if you need to start your large motor; if a lighting circuit used a Type D MCB, and you experience a fault, it may take too long to trip and protect the wiring. Be careful to ensure that the MCB is the proper trip curve for the load that it is protecting; if you are unsure, it is usually safer to use the next higher trip curve rather than to use a higher current rating on the same trip curve.
The main types of circuit breakers
Breakers can be split into different categories based on how they were made (type of construction), function (how they work), voltage rating, and number of poles. The following are the different types of breakers that you will see in use.
| Тип | Full name | Typical rating | Where you find it |
|---|---|---|---|
| МCB | Miniature Circuit Breaker | 0.5-125 A | Residential consumer units, small commercial distribution boards |
| MCCB | Molded Case Circuit Breaker | 16-1,600 A | Commercial panels, industrial feeders, large HVAC and machinery |
| ACB | Воздушный автоматический выключатель | 400-6,300 A | Industrial switchgear, generator and main incomers, data centers |
| VCB | Vacuum Circuit Breaker | Up to 40 kV class | Medium-voltage distribution, substations, motor switching |
| RCCB / ELCB | Residual Current Circuit Breaker / Earth Leakage | 25-100 A, 30-300 mA sensitivity | Shock protection on sockets and wet areas |
| RCBO | Residual Current Breaker with Overcurrent | 6-63 A | Combines MCB + RCCB in one module |
| GFCI / AFCI | Ground-Fault / Arc-Fault Circuit Interrupter | 15-50 A | US kitchens, baths, outdoors (GFCI); bedrooms, living areas (AFCI) |
| SF6 / Oil | Gas- or oil-insulated breaker | Высокое напряжение | Transmission networks, high-voltage substations |
There are two major points of confusion: First, RCCBs and RCBOs are not overcurrent protective devices as most people think of them; rather, they are devices that detect leakage current to ground (through either a person or the insulation), so they will interrupt the circuit within approximately thirty milliseconds after the leakage has occurred. Therefore, under current codes, all sockets should have RCCBs or RCBOs installed. Secondly, in U.S. residential wiring, the functions of AFCI’s and GFCI’s are often combined within the same device when required in bedrooms/living spaces under current code provisions.The relationship between these residual-current and overcurrent devices is explained in more depth in our RCCB vs RCBO guide.
Breakers can have a single-pole (one 120V leg), double-pole (two legs for 240V appliances/mains in North America) or three- or four-pole (three phases of industrial/commercial power) configurations. Single-pole breakers provide overcurrent protection for 120 Volt branch circuits; Double-pole breakers provide overcurrent protection for 240 Volt loads such as clothes dryers, ranges, water heaters and Electric Vehicle chargers and will trip both legs at the same time. Many of the most common mistakes made by DIY homeowners are due to improper selection of the number of poles, hence it is recommended that you have an experienced professional perform panel installations/housing upgrades as they have completed this process hundreds of times before.
Circuit breaker vs fuse: what is the difference?
Apart from serving the same purpose to provide protection for wiring and equipment, each type has a unique method of operation. A fuse’s ability to protect against an overload condition is through a metal conductor that melts at an amperage above its capacity, creating a physical break in the electrical circuit. In a breaker, this process is completed through mechanical movement of the switch. This difference creates the foundation for the comparisons between these two types of protective devices.
| Property | Предохранитель | Автоматический выключатель |
|---|---|---|
| After a trip | Element destroyed — must be replaced | Reset by flipping the handle — reusable |
| Response speed | Extremely fast (good current limiting) | Fast, but slightly slower than an equivalent fuse on very high faults |
| Tamper protection | Easy to defeat by fitting a larger fuse or a coin behind one | Harder to defeat; trips recur visibly |
| Resettable remotely? | No — physical replacement | Some industrial types can be reclosed electrically |
| Cost per event | Cheap part, but every fault costs a new fuse | Higher first cost, near-zero cost per trip |
| Discrimination/selectivity | Good; fuses coordinate well in series | Needs careful grading between upstream and downstream units |
| Where preferred | Semiconductor protection, high-fault-capacity industrial spots, some automotive/marine | Everywhere else — homes, commercial, industrial distribution |
Most users would conclude that an upgrade from a fuse box to a circuit breaker panel is the best return on their investment. A fuse does not provide any indication of repetitive overloading of the circuit and therefore provides opportunities for unsafe and/or hazardous repairs; on the other hand, with a circuit breaker, the user can clearly identify the circuit that tripped and can simply reset it. Circuit breakers also offer ground fault and arc fault protection, features that cannot be offered by any type of fuse. In some instances, a fuse will out-perform a circuit breaker, such as when dealing with very high fault currents or the need for rapid current limitation while protecting sensitive electrical equipment; however, in buildings, circuit breakers have been the best choice for many years.
Circuit breaker vs switch: what is the difference?
A breaker handle is often mistaken for a switch because they are similar, but they are different types of devices. A switch (e.g., light switch, isolator, contactor) is intended to be regularly used or operated (you will turn it on/off many times), and it does not have any ability to sense. A circuit breaker, on the other hand, is intended for infrequent service and is specifically designed to automatically trip when it detects a fault by automatically shutting off the current.
As a result of these differences, there are two basic rules. First, a switch does not protect you from faults; it can only control your circuit, and therefore the circuit that comes from a switch must be protected by other devices upstream of the switch. Second, a circuit breaker is not intended for daily switching; its contacts are not designed for thousands of operates, and each time you manually trip it, the life expectancy of that breaker is decreased. If you want to have a switching device and also provide some form of protection, the ideal product would be a switch disconnector with a fuse or circuit breaker, or a motor protective circuit breaker (for machine circuits). On the high-voltage side, this difference is also found in substations, where they use separate disconnectors for switching (they will only switch when there is no current) and circuit breakers for interrupting fault currents.
Main breaker vs branch circuit breaker: what is the difference?
People frequently confuse the two types of breakers in a breaker panel (the main and the branch) because they both disconnect electricity from a panel; however, they serve entirely different functions. The main breaker disconnects power to the entire panel from the electrical utility, while branch breakers (the long rows of 15- and 20-amp handles) protect each individual circuit (e.g., kitchen, bedrooms, AC unit, dryer). Depending on the size of a person’s home and how much electricity is used each day, many people will find that the main breaker will be rated between 100-200 amps in a home.
Understanding the distinction between these two breakers is vital because of how they help protect against electrical shock and fire. The main breaker protects the service conductors, giving firefighters and/or electricians a single safe way to disconnect power from a building, whereas branch breakers protect the smaller wires located within walls that run to each particular room; therefore, when an electrical short or failure occurs within a branch breaker, it can potentially only take one room out of service instead of the entire house. When an individual hears “the main breaker tripped,” it usually indicates that either the total electricity usage exceeded the service capacity or that a significant electrical fault occurred between the main and branch breakers. Therefore, before an individual resets the main breaker, they should unplug enough appliances or electronic devices to bring the total electricity consumption below the maximum rating of the breaker panel.
Which brands make circuit breakers?
There are two distinct categories of manufacturers in the circuit breaker industry: global players with an extensive presence in North America and Europe, and companies focused on niche products where their certified products can be found across the globe.
| Бренд | Home market | Known for |
|---|---|---|
| Square D (Schneider Electric) | US / France | QO and Homeline panels — the most widely installed residential breakers in North America |
| Eaton (incl. Cutler-Hammer) | US / Ireland | BR and CH series, strong commercial and industrial line |
| Сименс | Germany | Huge industrial and residential portfolio, MP/QP residential line |
| ABB | Switzerland / Sweden | Tmax MCCB range, global industrial standard, SACE breakers |
| Eaton CH | US | Residential breakers plus a growing smart/connected breaker line |
| General Electric (now part of ABB/Smart Breaker brands) | US | Legacy THQL/THQB panels still common in older homes |
| Legrand / Hager / Chint / HUYU and similar certified global manufacturers | Europe / China | Full MCB/MCCB/RCBO ranges certified to IEC 60898 and IEC 60947, supplying OEM and project markets worldwide |
When purchasing circuit breakers, the most important rule regarding product compatibility is that, in North America, circuit breakers are panel-specific. As an example, a Square D breaker will not fit an Eaton panel, and trying to install one in a panel that it is not intended for creates not only a code violation, but also a legitimate fire hazard. To avoid this issue, simply match the replacement circuit breaker to the manufacturer’s name and series of the existing panel (see our Eaton vs. Cutler-Hammer Reference Guide for product compatibility) or, if you choose to switch brands, you can simply replace the entire panel. Circuit breakers from different manufacturers are compatible and can be mounted on DIN-rail tracks in markets outside of North America (i.e., IEC markets), and therefore companies like HUYU can distribute their certified miniature circuit breakers (MCBs) in over 100 countries. For industrial and project clients, the certification is much more important than the product logo; the certification for North America is UL 489 for circuit breakers, IEC 60898 for MCBs, IEC 60947-2 for molded case circuit breakers (MCCBs) and air circuit breakers (ACBs), and the certified test reports for those certifications.
How much do circuit breakers cost?
Pricing for Breaker varies more than many other types of electrical components because circuit breakers can range from $6 (residential spare) to over $100,000 (transmission). Therefore, when creating a budget for a project, it helps to have a breakdown of the possible price ranges in each category for each year leading up to 2026:
| Тип выключателя | Part cost (typical) | Installed cost (electrician) |
|---|---|---|
| Standard single-pole thermal-magnetic (15-30 A) | $6-18 | $130-250 including service call |
| Double-pole (30-100 A) | $10-40 | $150-300 |
| GFCI breaker | $40-100 | $200-350 |
| AFCI or combination AFCI/GFCI | $30-100 | $175-350 |
| Smart breaker with energy monitoring | $50-300+ | $250-500 |
| MCB (IEC, 6-63 A, DIN-rail) | $3-25 | Varies by market |
| MCCB (100-1,600 A) | $45-1,600+ | Project-priced |
| ACB (630-6,300 A) | $800-5,000+ | Project-priced |
| Medium/high-voltage breaker | $5,000-100,000+ | Substation projects |
The big price drivers are amperage, interrupting rating, protection features, and brand. A basic 20 A thermal-magnetic breaker at $6-12 versus a combination AFCI/GFCI unit at $50-100 is roughly a five-to-eight-times multiplier — justified by the microprocessors and sensors inside the smart unit. The full cost picture — including panel replacement and when a $200 breaker swap turns into a $2,000-4,000 panel upgrade — is detailed in our руководство по стоимости замены автоматических выключателей.
How to choose the right circuit breaker
To select a new circuit breaker, follow these five steps IN ORDER: Each step limits and restricts your options for the next step.
- Wire ampacity = Breaker amperage, NOT appliance amperage! The Industry Standards state that the breaker is there to protect the wire, so the breaker should NEVER exceed the ampacity of that wire. Therefore, a 15 amp breaker protects a 14 AWG copper wire, a 20 amp breaker protects a 12 AWG wire, and a 30 amp breaker protects a 10 AWG wire. NEVER upgrade a breaker to eliminate nuisance trips until you have verified the wire size; this is one of the leading causes of houses burning down.
- 80% of Breaker’s Rating is Maximum Continuous Load: The National Electrical Code requires circuit breakers to be rated for continuous (3-hour or more) loads at no more than 80% of the breaker’s capacity. A continuous 12 amps (1,440 watts at 120 volts) on a 15 amp breaker are fine, and 16 amps (1,920 watts) on a 20 amp breaker are fine. For an explanation of how to perform the calculation converting watts-to-amps for continuous loads, please see our 15-Amp Circuit Capacity Guide.
- Type Matches Hazard: A Ground Fault Circuit Interrupter (GFCI) circuit breaker must be used on receptacles located in kitchens, bathrooms, garages, and outside. An Arc Fault Circuit Interrupter (AFCI) breaker must be used in bedrooms and living areas under current code. Lastly, a motor or transformer circuit must use the proper trip curve (usually C or D) to minimize nuisance trips during startup.
- Number of Poles = Voltage: A single pole breaker is used on 120-volt branch circuits; a double pole breaker is used on 240-volt loads and on disconnects from the service panel; a breaker for a three-phase system must be either a three- or four-pole breaker.
- Interrupting Rating and Certifications: The interrupting or breaking capacity (kA) of a circuit breaker must be adequate for the available fault current at the main panel, and ONLY certified devices (in North America, the certification mark is UL 489; in the rest of the world, the certification marks are IEC 60898/60947) should be purchased from authorized dealers. Counterfeit breakers are an increasing problem. When counterfeit breakers fail, it is usually during a fire.
Installation, resetting, and replacement
Resetting a tripped circuit breaker is something every homeowner ought to be aware of. When a circuit breaker trips, it will revert to the middle or OFF position on its handle. To reset the circuit breaker, turn the handle completely to the OFF position, and then fully back to the ON position. If after you have reset the circuit breaker it does not trip again, it is likely that the overload causing the circuit breaker to trip was an isolated event. If the circuit breaker trips again immediately after being reset, you most likely have a larger electrical issue, and you should stop attempting to reset the breaker and investigate the problem further.
Circuit breakers do eventually wear out, and the wear will usually result from a mechanical failure in the latching mechanism or the electrical contacts rather than a failure of the sensing mechanism (the electronic part). A circuit breaker that is very hot, buzzing or humming, has a burnt smell, and/or has tripped many more times than it previously did, or has failed to trip completely, is likely going to need to be replaced. Testing a faulty breaker is fairly easy if you have access to a multimeter; you’ll need to check that the breaker will hold the correct amount of current load and trip when it is supposed to. But if a circuit breaker begins showing any of the above warning signs, it will be in your best interest to replace it instead of trying to continue using it until it finally does fail on you.
Replacing a circuit breaker in a panel that is live has some inherent risk involved. Depending on the configuration of your panel and where the service lugs (terminals) on your circuit breaker panel are mounted, the service lugs remain energized even when the main has been turned OFF. In the vast majority of cases in the United States, it is against the law to rewire or replace a circuit breaker while working on the live side of the service because there is a high likelihood that an arc flash will occur if you come into contact with the energized lugs while doing so. The cost of hiring an electrician to replace a circuit breaker is typically between $130-$250 to provide you with peace of mind and protection against the risk of an arc flash. The same professional judgment should be applied on the panel level: whether or not your aging 100 A service is capable of handling the entire electrical load of a modern home, and whether or not the current code requires you to have a panel rated at 200 A, is a question that you should be able to have answered by a licensed electrician after a load calculation has been performed, not a guess.
Why does a circuit breaker keep tripping?
A repeatedly tripping breaker is not the source of the problem; it is an indication of a problem. A tripped breaker indicates that there is something wrong with the electrical circuit or with what is connected to it. Identifying the cause of the problem means understanding the following four major categories of electrical faults or problems.
- Overloaded circuit – Too many appliances or devices drawing power from a single circuit are causing an overload of electrical current. The solution to this is to balance the load on the circuit or to install a new circuit for the additional high-wattage electrical devices, and not to use a higher-rated circuit breaker.
- Короткое замыкание – An electrical short happens when an energized wire touches either a neutral or ground wire. This condition can happen inside an appliance or in an extension cord when either the cord or the appliance is damaged. A short circuit will usually trip instantly, and there may be a burnt smell associated with it.
- Ground Fault – A ground fault occurs when current leaks to ground (earth) through a person, water, or damaged insulation on an electric wire. Ground fault protection devices (GFCIs and RCCBs) are critically important to ensure the safety of people using electricity.
- A Breaker Failure – After decades and thousands of operations, a breaker eventually will wear out and will no longer trip and will fail to hold on to its rated current.
Diagnosing which family you are in — and why a breaker that “trips for no reason” almost always has a reason — is exactly what our circuit breaker tripping guide walks through step by step. It is important to note: If a breaker trips when an appliance is plugged in, the appliance is most likely the cause. If a breaker trips when nothing is connected, suspect either the wiring or the breaker and call a licensed electrician to investigate further; do not experiment with either the wire or the breaker.
Часто задаваемые вопросы
How do I reset a circuit breaker?
To reset the circuit breaker(s), locate the circuit breaker that tripped (the lever/circuit breaker will be in between the OFF/ON position) Move the lever fully to the OFF position, and then move it firmly to the ON position. If the circuit breaker(s) remains in the ON position, then the trip was probably a temporary overload. However, if the circuit breaker(s) immediately or shortly thereafter trips again, do not reset the circuit breaker(s) again and contact a professional to determine why the circuit breaker(s) keep tripping.
What’s the difference between a circuit breaker and a fuse?
Fuses protect electrical circuits by melting a wire (metal element), and therefore, when a fuse is blown it has to be replaced every time. Circuit breakers protect electrical circuits by using a mechanical switch to open the circuit. This allows circuit breakers to be reset and reused many times. Additionally, circuit breakers have the ability to provide both ground fault protection and arc fault protection which fuses cannot; therefore, circuit breakers have replaced fuses in virtually all modern buildings.
What is the difference between a main breaker and a circuit breaker?
The term circuit breaker refers to all circuit breakers. The main breaker is a circuit breaker that is larger than the others (typically 100-200 amps) that disconnects the entire electrical service from the utility company. Branch circuit breakers are the smaller circuit breakers that are used to protect individual circuits in the building. All circuit breakers will trip automatically in response to electrical faults, however, the main circuit breaker protects the conductors that carry the electrical service, while branch circuit breakers protect single circuits.
What is the difference between a circuit breaker and a switch?
A switch is a manual control device that is intended for frequent operation, without providing any protective function. A circuit breaker is a protective device that will automatically open the circuit if there is an overload condition or short circuit and is not intended to be used thousands of times a day. A switch does not provide protection for a circuit; a circuit breaker is not intended for daily use. Some devices are designed to have both functions; therefore, these products are referred to as switch-disconnectors or motor-protective devices.
Ссылки
- Schneider Electric — What Is a Circuit Breaker?
- Eaton — Circuit Breaker Fundamentals
- RealPars — Circuit Breakers Explained
- Family Handyman — How Circuit Breakers Work
- NFPA — National Electrical Code (NEC)
Заключение
A circuit breaker protects every electrical system from excessive voltage and current. It is a switch that automatically responds to excessive voltage and/or current (i.e. thermal and magnetic overload) and opens the circuit as fast or faster than a fused circuit. If you are new to circuit breakers, it is important to understand the thermal/magnetic trip mechanism that opens the breaker, the trip characteristics of breakers of types B, C, and D according to their rated load and type of electrical load, how do MCBs, MCCBs, RCBOs differ; when and why you should use circuit breakers instead of fuses; and to what extent you should use the main breaker with regard to branch circuit breakers; how to determine the correct certification for the circuit breaker and the manufacturer of the circuit breaker to ensure compatibility with your circuit breaker panel; and how to use the ratings of circuit breakers to size correctly the circuit breaker for your installation. All of the above may be obtained from the circuit breaker manufacturer or an electrical contractor, and if not, you must refer to a qualified electrical contractor to obtain such information to ensure your equipment remains protected by the circuit breakers. Assuming that you have taken advantage of the above information, you can expect your circuit breaker(s) to continue protecting all of your equipment for many years to come until such time as the circuit breakers have reached their rated life (which they do not use) and have provided the necessary protection for each piece of your equipment.
