How to connect a differential circuit breaker

An automatic differential switch is required to protect the power line from overvoltage and short circuit. An electromechanical device also protects a person from electric shock in the presence of a leak. The connection diagram of the difavtomat is selected taking into account the number of phases of the network and the specifics of the device (functions of the RCD and the circuit breaker).

Features of the design of differential machines

The combined instrument consists of two main units:

• A circuit breaker with two releases. The electromagnetic coil provides power off in the line in case of short circuits. A thermal release in the form of a bimetallic plate is needed to de-energize the network in case of an increase in the load limit. The devices have 2 (single-phase network) or 4 poles (three-phase network);
• RCD. The protective shutdown element does not allow the line to be disconnected due to the relay. Under normal conditions, the node generates magnetic fluxes of equal strength. In the presence of a leakage current, the relay switches, de-energizing the network.

In addition to the RCD and AV, the difavtomat includes a differential transformer and an electronic amplifier.

Advantages and disadvantages of devices

Differential automatic devices under conditions of correct installation provide reliable protection of the power line. When buying a device with a nominal current of 16, 20, 25, 32 Amperes, you do not need an additional RCD.

The disadvantages include the lack of a flag marker for models of some manufacturers. Without this designation, it is difficult to establish the reason for the power off.

Current parameters for household networks

According to the parameters of the current for the operation of the protection, the devices are divided into classes:

• B - permissible load 5 times;
• C - permissible load 10 times;
• D - permissible load 20 times.

With a minimum equipment capacity, B-class devices are suitable, for an apartment or private house - C-class.

For household power lines, C16 difavtomats are mainly used. When organizing lighting, models with a current leakage rating of up to 30 mA are used. Single lines are equipped with 10 mA devices. Devices with a leakage current of up to 300 mA can be placed on the input.

Installation of a difavtomat in a three- and single-phase network

The installation of the device begins by checking the leak response. The user will need to press the Test key, creating an artificial leak. The device must react, i.e. turn off. If he continued to work in test mode, the machine cannot be used.

For a single-phase network with a voltage of 220 V, a two-pole RCBO is used:

• the neutral wire from the load is connected from below;
• the neutral from the supply is thrown from above.

The three-phase type of network with an operating voltage of 380 V provides for a four-pole device connected according to a similar principle. During installation work, it must be borne in mind that a bulky differential protection unit will take place in the shield.

Devices marked 230 / 400V may be connected to a single- and three-phase network.In the latter case - for separate equipment or outlet group.

Rules for choosing a connection diagram

When connecting a difavtomat, you need to focus on the network parameters, type of premises and financial capabilities.

Easy connection

A house in a rural area or a summer cottage does not need a lot of devices. In a suburban building, it is enough to put one device at the input and bring out separate lines for the lighting system and sockets. In the presence of a leakage current on any line, the common RCBO will operate, de-energizing all lines.

Until the end of the elimination of the breakdown, there will be no electricity in the house.

Reliable connection

In an apartment or a country cottage for risk groups, you will need to connect separate devices. Bathroom, kitchen, appliances that use water need increased security. For "wet groups", a separate wiring with an individual diaphatomat is organized. At the moment of triggering, the device de-energizes only the problem segment, the rest of the network section works as usual.

Branched network protection

For a complex power line, you will need class S or G diphatomat. They have a linear connection principle:

• a separate machine for a group of consumers;
• individual machine for high-power consumer.

At the moment of operation of one linear device, the others will function normally. The reason lies in the delay in the response time of the machine to the entrance.

Connection diagrams

Regardless of the circuit, the circuit breakers are connected to the phase or neutral of only the circuit for which they are needed to protect.

RCBO at the input

The device is installed in the shield and protects the branches of the wiring and the groups to which it is thrown. An introductory machine must be selected taking into account the power and operating characteristics of the network. First, the counter is put, and then the apparatus. All electrical circuits are connected to the output of the RCBO. An individual limit switch is installed for each circuit.

The current load must be selected taking into account the power of the household appliances switched on at the same time and the parameters of the electric meter. The machine must be triggered earlier than the metering device fuse.

This connection has several advantages:

• saving money on the purchase of one device;
• compactness of the shield - the machine does not take up much space.

Disadvantages of connection - a long search for a faulty branch, the reasons for the failure and a complete de-energization of the premises in case of problems.

Two-level connection

The machine must be connected to the extensive network in stages. At the first level, after the counter, a RCBO is placed - the main load passes through it. Output cables are thrown onto the machines according to the number of room contours.

At the second level, low-power devices with a minimum leakage current threshold can be connected. A separate circuit will need to be allocated for a washing appliance, a jacuzzi, an electrically heated shower stall.

The two-tier system has several advantages:

• safety - the network is protected from voltage surges and short circuits;
• reliability - the device of the first level duplicates the work of subsequent RCDs and turns off the energy simultaneously with them;
• fast detection of a faulty area;
• de-energizing only one room during the repair;
• the possibility of implementation with a multi-circuit branched line.

The disadvantage of the scheme is the cost of purchasing difavtomats and finding a place for their installation.

Single-tier connection type

The connection is similar to a single-level connection with the difference that a common device is not installed. A patch bus is used for cable management and ease of installation. The disadvantage of this method is the absence of a backup device with additional protection.

A single-level scheme is suitable for a branched network with several circuits.

Installation of difavtomats without grounding

Grounding was not provided for in old buildings, so today there are risks of electric shock to residents and equipment breakdowns.

The peculiarity of connecting a protective difavtomat to an ungrounded single-phase or three-phase network is the functional replacement of the ground wire by the device. After detecting a leakage current, the circuit is quickly broken. The device provides additional protection for household appliances from the effects of voltage surges or short circuits.

Features of the circuit for a three-phase line

A three-phase network with a voltage of 380 V is organized in shops, garages, industrial premises. In order to correctly and quickly connect a protective difavtomat, it is necessary to take into account the algorithm for the 220 V line.

The wires are connected by clamping terminals according to the markings on the device case:

• phase wire is designated with the letter L;
• neutral cable is marked as N;
• the number 1 is used to designate the lead-in conductor;
• the outlet wire is designated by number 2.

The electrical circuit of the circuit for a three-phase line must have an earth conductor.

The nuances of installing selective models

The use of a selective difavtomat as the main device is permissible only in a two-level scheme. The device marked S has a longer response time and deactivates the second level devices without disconnecting the line.

Selective devices can be connected as follows:

• the leakage current is fixed by automatic devices of two levels, triggered by the principle of randomness;
• if the response time of the main RCBO is longer, the device of the second level works first;
• in the event of a breakdown, one circuit is de-energized, the rest of the line is energized.

The selectivity principle allows the use of difavtomats with a similar leakage current threshold.

Memo for connecting a differential machine

Regardless of the number of network phases, you need to know how to properly connect the machine:

• Power cables are thrown at the top, wires to consumers are at the bottom. In order not to get confused, you can see the type of connector and the diagram on the AB case.
• Long cables should be replaced or lengthened to prevent burnout.
• Observing the polarity of the contacts ensures that the machine responds correctly to network failures.
• Zero contacts are not connected to a common jumper. The neutral should only feed its own branch.
• The operating temperature range of the machines is 6-34 degrees. For outdoor installations, models with a moisture resistant housing are used.
• Modifications with a breaking capacity of 6000 amperes are installed in an apartment or house, remote from the substation, next to the substations - for 1000 A. If the place of residence is a village with an overhead power line, a device for 4500 A will suffice.

The device can be turned over on a din rail and photographed so as not to get confused in the future.

Connection algorithm

Step-by-step process for connecting circuit breakers in an apartment switchboard:

1. Visual inspection of the device body for defects.
2. De-energizing the apartment switchboard by pressing the main switch down.
3. Checking the absence of voltage of all contacts with an indicator screwdriver.
4. Fixing the machine on the mounting rail with a latch on the back of the case.
5. Removing the conductor insulation with side cutters.
6. Pressing open ends with sleeves.
7. Phase and neutral connection - from the supply wire to the upper terminals and from the selected network to the lower terminals.

At the end of the work, you will need to turn on the voltage and test the machine.

Popular RCBO connection errors

After installation, the difavtomat may not turn on or immediately knock out. Errors of novice masters lead to similar phenomena:

1. Combining protective zero (ground) and working zero (neutral) in a separate area. The device does not turn on, the handle at the top is not fixed.
2. The use of zero load for low-level automata not from the output, but from the zero bus. The switches are brought into the operating position, but they are turned off when the load is applied.
3. The zero at the output is not brought to the load, but is returned to the bus. Zero load is taken from the bus. The switches are in the working position, after pressing the test key, the difavtomat turns off.
4. The cable from the zero bus goes to the bottom terminal with the letter N, the wire does not go to the load. With active circuit breakers, the "Test" button does not work, operation is possible when voltage is applied.
5. The neutrals of the two devices are reversed. Both are activated, the test button works. When the load is applied, both difavtomats are turned off.
6. Connection of zeros from two machines at any site. The circuit breakers go up, but when you press the test key of one device or when the load is applied, both are turned off.

To fix the failures, you will need to reconnect.

Self-connection of a protective differential circuit breaker will not be difficult for a person with skills who follows the scheme. A memo and a list of basic connection errors will help you avoid device malfunctions.