Marking circuit breakers: how to choose the right machine for wiring

Automatic machines installed in apartment electrical panels are designed for emergency power outages in the event of a short circuit or excess load on the circuit. They can also be controlled manually when it is necessary to change the switch.

What parameters the device has will tell you the marking of circuit breakers, presented in the form of names, alphanumeric designations and schemes. Agree, the ability to “read” the inscription will be useful to the home master if it is necessary to replace the device, eliminate breakdowns or connect an additional machine.

We will help you figure out what's what. The article describes the detailed decoding of the marking block on the switches, as well as provides recommendations for choosing a machine, taking into account its characteristics.

Why marking is necessary

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 value of the rated current. An experienced installer easily distinguishes between devices that are exactly the same from the point of view of the layman.

The homeowner, unfamiliar with the intricacies of the electrical installation craft, can also figure out the information provided by the manufacturer.

Using the special symbols located on the front panel, you can to distinguish a machine from an RCD, find out its main technical characteristics and find out in what sequence the wires are connected.

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

Information on a separate circuit breaker may be required if:

• it is necessary to replace the device;
• should pick up 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 circuit breaker;
• need to find the cause of the emergency shutdown, etc.

Some characters become intuitive, and some knowledge is needed to decrypt others. If you plan to independently replace the wiring or connect circuit breaker, instrument information is best studied in advance.

What do the inscriptions on the switch mean

Symbols, numbers, letters, schemes are applied to technical plastic with a special indelible paint. Even with older models, they remain readable. It is assumed that the user or electrician, having hardly glanced at the machine, must quickly determine its current characteristics and voltage.

Manufacturer and model of the machine

The top line of the marking block is the brand name. For printing, a certain color is selected, often bright, and sometimes even by shade you can determine which manufacturer’s products are in front of you.

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

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

The line below indicates the model of the device. All other labels, except for the name of the manufacturer, are usually printed in gray, so the series can be easily confused with the technical specifications.

In order not to be mistaken, we look precisely at the second line. The designation of a ruler or model may have the following form: BA63, SH200, Acti9.

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

Models from the VA47-29 series have more than two hundred standard designs, while they are not tied to specific rated currents - they can be 0.5 A, 5 A, and 63 A

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

Definition of time-current characteristic

The next line is a combination of a Latin letter and a number. The letter, standing first, just indicates the time-current characteristic. It indicates how quickly the circuit breaker trips with a certain current flowing through it. There are five different types in total: "B", "C", "D", "K", "Z", however, machines B, C, D are used in everyday life.

The dependence of values ​​is often presented in the form of graphs that can be found on the Internet. They have the following form:

The graph shows how the speed of the machine depends on the multiplicity of the current to its rated value. The 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 - C, between 10 and 20 - D.

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

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

What does it look like in practice? Suppose the current increased sharply to 100 A. B16 will turn off instantly, since 80 A is enough for it, and for C16 to work, it takes some time to heat the plate. Then thermal protection starts to operate, 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 (BTX) indicates machine rating. The rated current indicates at which max value the machine will be in operating condition, that is, the current will freely pass through it without an emergency shutdown.

An important point: these data are relevant only at a certain temperature, namely + 30ºС. If the temperature is higher, the circuit breaker may trip at a lower current value.

The indicated value 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 operation inside the device. The machine switches off due to the operation of two types of circuit breakers - thermal and magnetic.

The first is included in the work if an overload has occurred in the power supply network. A current value 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% so that a break occurs.

But in addition to network congestion, a phenomenon such as overcurrent also occurs. The reason for its appearance is a short circuit. Already not thermal, but an electromagnetic release reacts to overcurrents.

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

To protect wiring and your own life from overload and short circuits, it is recommended that you purchase only high-quality protection devices.

Marking of rated voltage and frequency

The line below shows the value of the rated voltage. It also needs to be observed when choosing a device without fail. The marking can be determined by the unit of measurement - Volts, which are indicated by the letters V or B. For accuracy, the following icons are also used: “-” - constant voltage, “~” - variable.

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

The frequency is determined 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 in the manual, which lists all the technical data about the device.

Tripping Current Limit

The next value indicated on the machine case is the tripping current, which is also called the breaking capacity of the device.

If suddenly a short circuit occurs and an overcurrent appears in the circuit, the machine will operate in emergency mode, but at the same time fully retain its functionality. You can notice that the trip current is several times higher than the nominal value.

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

The example of the designation of the trip current is the number 4500 in a black frame, located directly below the voltage and frequency values. On some models, this parameter is not specified.

In addition to the value of 4500 A, which is typical for many machines of the household class, you can find 6000 A and 10000 A.

What is current limiting class?

Immediately below the breaking current, there is a current limiting class. It is easy to find on the panel - this is the number 1.2 or 3, enclosed in a black square. During a short circuit and the appearance of an overcurrent in the network, the system may be damaged.

The faster the machine operates, the sooner the exposure to thermal energy, which is a consequence of the occurrence of overcurrent, ceases, the faster stability comes.

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

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

Grades:

• 1 class - limitation> 10 ms;
• 2nd grade - from 6 to 10 ms;
• 3rd grade - 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 main characteristics, you can find a connection diagram. Usually it is located on the right side of the front panel.

The circuit diagram shows the circuitry, including trip units and contacts, to which the wiring is connected. Use numbers to indicate contacts

The circuits on 1-pole and 2-pole devices are different. On the second, in addition to the circuit with the contacts, there is a marking of the terminals, as well as on some models, the N icon denotes 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 the markings on the front panel.

Designation cheat sheet. Not all manufacturers provide technical information in full, so you must first study the documentation for the device (+)

In addition to the disassembled characteristics, you should know other nuances of choice. For example, before buying an automatic machine, its power is necessarily calculated and the required number of poles is selected.

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

The brand is important, as well as the condition of the wiring.

Recommended to make a purchase in a specialized store. But recently, it has become common practice to acquire 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 chip or crack can cause damage, and mechanical damage is also a sign 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 find out about the intricacies known only to professionals.

How is the machine arranged and working:

More about thermal values ​​- analysis of the table:

We read the marking with a specialist:

Correctly choosing and connecting a home electrical protection device helps marking directly on the device. The ability to decipher symbols and correctly determine the characteristics will help in the future with the self-assembly of a new circuit.

Is there anything to supplement, or have questions about decoding the marking of circuit breakers? You can leave comments on the publication and participate in discussions. The contact form is located in the lower block.