Circuit Breaker Markings: Specificity of Alphanumeric Designations

Automatic devices installed in apartment electrical panels are intended for emergency power outages in the event of a short circuit or overload on the circuit. They can be controlled manually when the switch needs to be changed.

What parameters the device possesses will be indicated by the labeling of the circuit breakers presented in the form of names, alphanumeric designations and diagrams. Agree, the ability to “read” the inscription will be useful to the home master if you need to replace the device, repair the breakdowns or connect an additional machine gun.

We will help you figure out what's what. The article describes the detailed interpretation of the marking unit on the switches, and also gives recommendations on the choice of the machine with regard to its characteristics.

The content of the article:

  • What labeling is needed
  • What do the labels on the switch mean?
    • Manufacturer and model of the machine
    • Determination of time-current characteristics
    • Rated current and its designation
    • Marking of rated voltage and frequency
    • Trip Current Limit
    • What is the current limit class
    • Wiring diagram
  • Tips for choosing a circuit breaker
  • Conclusions and useful video on the topic

What labeling is needed

For a qualified electrician, the front panel of the machine is like an open book - in a couple of minutes he can learn everything about the device, from the manufacturer to the rated current value. An experienced installer easily distinguishes between devices that are absolutely identical from the point of view of the average person.

A homeowner who is unfamiliar with the intricacies of electrical installation craft can also sort out the information provided by the manufacturer.

With the help of special symbols located on the front panel, you can distinguish the machine from the RCD, find out its main technical characteristics and find out in which sequence the wires are connected.

Marked machines on din-rail

To clarify the data on a specific device, it is enough to open the door of a metal cabinet in which metering and protection devices are installed: all symbols are visible

Information on a separate circuit breaker may be required if:

  • it is necessary to replace the device;
  • follows pick a new machine in connection with the appearance of an additional circuit;
  • it is required to compare the rated current load of the line and the switch;
  • need to find the cause of the emergency shutdown, etc.

Some characters are understood intuitively, to decipher others need some knowledge. If you want to replace the wiring yourself or connect a circuit breaker, information about the devices better to learn in advance.

What do the labels on the switch mean?

Symbols, numbers, letters, schemes are applied on technical plastic with a special indelible paint. Even the old models, they remain readable. It is assumed that the user or electrician, barely glancing at the machine, should quickly determine its current characteristics and voltage.

Manufacturer and model of the machine

The topmost line of the marking box is the brand name. For printing, a certain color was chosen, often bright, and sometimes even by shade it is possible to determine which manufacturer’s products are in front of you.

Color marking devices

The color of the inscription is usually repeated in the design of the control element - the lever with which the device is forcibly turned on or off. However, sometimes the pen is colored neutral gray or black.

Experienced electricians offer not to skimp on the purchase of machines and to purchase devices only proven European brands: Schrack technik, Schneider electric, ABB, Schaltbau, Moeller, Hager, Legrand. There are several Russian brands that can also be trusted: Electrician, TDM ELECTRIC, Ecf.

The line below indicates the device model. All other inscriptions, except the manufacturer's name, are usually printed in gray, so the series can be easily confused with the technical characteristics.

Not to be mistaken, we look at the second line. The designation of a ruler or model can be as follows: BA63, SH200, Acti9.

You can try to decipher the series, but not always the technical characteristics are hidden behind the letters and numbers, more often it is just the name of a particular model.

Model series BA47-29

Models from the series BA47-29 have more than two hundred standard executions, while they are not tied to certain nominal currents - they can be 0.5 a, and 5 A, and 63 A

The designation of a ruler can be printed both on a general gray background and on a color line, which is directly under the brand.

Determination of time-current characteristics

The next line is a combination of a Latin letter and a number. The letter that stands first, just denotes the time-current characteristic. It indicates how quickly the switch is triggered at a certain current strength flowing through it. In total there are five different types: “B”, “C”, “D”, “K”, “Z”; however, in everyday life, automata B, C, D are used.

Dependence of quantities is often presented in the form of graphs that can be found on the Internet. They have the following form:

Graph with the characteristics of machines

The graph shows how the speed of the automaton depends on the ratio of the effective current to its nominal value. Calculations obey the formula k = I / In (+)

Thus, if the value of k is between 3 and 5, this is category B, between 5 and 10 is C, between 10 and 20 is D.

Sample designation BTX on the body

Sample designation BTX on the instrument case. In the combination of "B16" B - this is the time-current characteristic, and 16 - rated current

If you take two switches with the same nominal current value, but with different actuation properties, they will also react differently. For comparison, consider C16 and B16. If we use the formula, then as a result we get for C16 - 80-160 A, and for B16 - 46-80 A.

How does it look in practice? Suppose the current has increased dramatically to 100 A. B16 will turn off instantly, since 80 A is enough for it, and in order for C16 to work, it takes some time to heat the plate. Then the thermal protection starts to act, and the machine turns off. The time difference usually takes a split second.

Rated current and its designation

The number to the right of the Latin letter (BTH) means automatic rating. The rated current indicates at which max value the machine will be in the active state, that is, the current will freely flow through it without emergency shutdown.

Important point: the specified data are relevant only at a certain temperature, namely + 30ºС. If the temperature is higher, the switch may operate at a lower current value.

Machine with a nominal 32A

The specified denomination is 32A. Therefore, under favorable conditions, the machine will not turn off until the current exceeds this value. But if the temperature rises, it can work at 25... 30A

Consider what happens during the operation inside the device. The automatic machine is turned off due to the operation of two types of trip units - thermal and magnetic.

The first is included in the work, if overload occurred in the mains. The value of the current above the nominal heats the bimetallic plate, it bends and breaks the circuit - the machine turns off. It is estimated that the load current must exceed the nominal by 15-55% for a break to occur.

But besides overload in the network, such a phenomenon as overcurrent occurs. The cause of its occurrence is a short circuit. It is not the thermal but the electromagnetic release that reacts to the overcurrent.

If the device is in working condition, then the operation occurs instantly, a maximum of 0.02 seconds. Delay in emergency shutdown leads to cable failure. The insulating layer melts first, then a fire may occur.

To protect the wiring and your own life from overloads and short circuits, and it is recommended to purchase only high-quality protection devices.

Marking of rated voltage and frequency

The line below shows the value of the rated voltage. It also must be observed when choosing a device on a mandatory basis. Marking can be determined by the unit of measurement - Volts, which are denoted by the letters V or B. For accuracy, the following icons are also used: “-” - constant voltage, “~” - alternating.

Nominal voltage designation

Option designation of rated voltage. If two digits are indicated, then the device can be used to protect 1-phase and 3-phase networks: 230V - for single-phase, 400V - for three-phase

Frequency is defined in Hertz and is designated as - 50 Hz. But it can not be found on the case, because almost all household appliances work in the same mode.

If you need to know exactly some characteristics of the machine, and their designations are not on the panel, you should look at the instruction, which lists all the technical data on the device.

Trip Current Limit

The next value, indicated on the case of the automaton, is the cut-off current, which is differently called the breaking capacity of the device.

If a short circuit suddenly occurs and an overcurrent appears in the circuit, the machine will operate in emergency mode, but it will fully retain its functionality. You may notice that the tripping current is several times higher than the nominal.

It is also possible that the value of the overcurrent will be higher than that indicated on the machine. Then there are no guarantees that the device will work correctly and will not suffer itself. Most likely, the magnetic release just will not cope with the load.

Break current designation

A sample of the current deactivation is the figure 4500 in a black frame, located directly below the values ​​of voltage and frequency. This option is not specified on some models.

In addition to the value of 4500 A, which is typical of many domestic-class machines, you can find 6000 A and 10,000 A.

What is the current limit class

Immediately under the cut-off current limit is the current-limiting class. It is easy to find on the panel - it is the number 1,2 or 3, enclosed in a black square. During a short circuit and an overcurrent in the network, the system may suffer.

The faster the automaton operates, the earlier the effect of thermal energy, which is a consequence of the occurrence of an overcurrent, ceases, and the sooner the stability comes.

Thus, the class of current limit shows the time interval to which the machine can limit the short circuit time.

Designation of current limiting class

Under the number 6000, the class of current limiting is clearly visible - 3. If there is no marking (and this is found in many models), then its value is 1

Division by class:

  • 1 class - restriction> 10 ms;
  • 2 class - from 6 to 10 ms;
  • 3 class - from 2.5 to 6 ms.

The third class is the most "fast" and preferred when choosing a machine.

Wiring diagram

On some circuit breakers, in addition to the basic characteristics, a wiring diagram can be detected. Usually it is located on the right side of the front panel.

Wiring diagram

The diagram shows the electrical circuit, including the releases and contacts, to which the wiring will be connected. To indicate contacts, use numbers.

Circuits for 1-pole and 2-pole devices are different. On the second, in addition to the circuit with contacts, there is a terminal marking, as well as on some models, the N symbol, indicating the connection of the zero core.

Tips for choosing a circuit breaker

The machine is selected based on certain characteristics, many of which can be recognized by marking on the front panel.

Marker layout

Cheat sheet for reading the notation. Not all manufacturers provide technical information in full, so you must first examine the device documentation (+)

In addition to the disassembled characteristics, you should know other nuances of choice. For example, before buying a machine, its power must be calculated and the necessary number of poles selected.

More information about the calculation and selection of the circuit breaker is written in this article.

Brand is important as well as the condition of the posting.

Image Gallery

A photo of

How to calculate the power of the device

Usually the decisive value is the rated current. To calculate it, the power of all household appliances is transferred from kW to W, added and divided into voltage (standard - 220V)

The number of poles of the domestic machine

A 1-pole model is suitable for lighting and outlet circuits, for high-power household appliances and units - 2-pole, for generator pumps - 3-pole, and 4-pole is used less often, for a network of 4 wires

Required availability of the second switch - RCD

In order for the protection to be complete, along with the automatic switches, an RCD is installed in the electrical panel. The device protects against leakage currents, that is, compensates for the shortcomings of the machine

Features of the connection of aluminum wires

Aluminum wiring is a rarity, but it is found in old houses. To connect it, use switches not higher than 16A. But it is better to modify the network and change the aluminum to copper.

How to calculate the power of the device

How to calculate the power of the device

The number of poles of the domestic machine

The number of poles of the domestic machine

Required availability of the second switch - RCD

Required availability of the second switch - RCD

Features of the connection of aluminum wires

Features of the connection of aluminum wires

Make a purchase is recommended in a specialized store. But recently, it has become common practice to purchase technical devices on commercial Internet sites, many of which are located in China.

When choosing, pay attention to the integrity and strength of the case. The slightest chipping or cracking can cause breakage, besides mechanical damage are signs of poor-quality material.

Conclusions and useful video on the topic

General information about the machines is disclosed above, and from interesting videos you can learn about the intricacies known only to professionals.

How the machine works and works:

More information about thermal ratings - analysis of the table:

We read the marking with a specialist:

Correctly select and connect the home mains protection device helps labeling directly on the body of the device. The ability to decipher the characters and correctly determine the characteristics will help in the future when installing a new circuit on your own.

Is there anything to add, or have any questions on deciphering the labeling of circuit breakers? You can leave comments on the publication and participate in discussions. The form for communication is in the lower block.

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