Types and technical characteristics of junction boxes

Junction boxes on the wall are electrical structures designed to protect communication electrical networks at their connection points from harmful environmental factors. Devices are mounted almost everywhere where cables or electrical wiring with a voltage of no more than 1000 V are switched.

Purpose and application

Junction box KF 0202 B, Hensel

There are many types of junction boxes. They may differ in shape, size, material of manufacture. However, they have the same task - to hide the content from destructive environmental factors. Each model is equipped with a cover.

The electrical installation design is used not only at home, but also in industry for fixing and branching wires when installing hidden wiring. There is a practice of installing such structures when conducting open wiring, but the appearance leaves much to be desired.

The main tasks facing the device:

  • Protection against mechanical, thermal and chemical influences.
  • Aesthetic design of electrical installation of cables at the junction of conductive conductors.

Tap-off boxes are most often used for lighting and power electrical lines of direct and alternating current with a voltage of no more than 660 V and low-current wiring. It is possible to mount structures not only indoors, but also outdoors.

Classification by type

Switching structures are divided into several types, depending on the purpose.

  • For connecting and protecting the joints of cable lines with a voltage of no more than 1 kW, for example, KOS, KRP, KVP, U997M, U994, U197, etc. They can also be installed together with the UHL system.
  • A box with a standard size (100 * 100 * 50 mm) is used for open and hidden wiring at home. For example, KO100, KTO100, KU100, KT100, KS100, KM100.
  • Branch structures intended for storage and protection of connection points of wire broadcasting lines UK2R and UK2P.

Also, according to the type of construction, they are divided into broaching and cable for overhead lines and junction boxes to the busbar (SHRA).

Protection class

The main characteristics of the branch boxes include the protection class in accordance with GOST No. 1425496. It has the form IPXX, where the last two combinations are numerical designations. The first number indicates resistance to dust, and the second indicates moisture resistance.

The codeDust protectionMoisture protection
0No protection providedNo protection provided
1The possibility of penetration of particles larger than 50 mm is excludedThe design is protected from vertically falling drops, such as rain, condensation
2The possibility of particles larger than 12 mm falling under the box cover is excludedThe box is protected from moisture ingress inside at an angle of 15 degrees
3Particles larger than 2.5 mm are not allowed to enterThe device is protected from drops, the angle of incidence of which is not more than 60 degrees
4Prevent ingress of particles larger than 1 mmFull protection of the box from splashes and drops is provided
5The unit is protected from dust depositsFull protection against water jets
6There is no possibility of dust getting under the cover of the structureProtection against high pressure water jets
7Protection of the structure when fully immersed in a humid environment to a depth of no more than 1 meter (short-term sinking in a humid environment)
8The design is completely sealed and can be operated underwater

Dust- and moisture-proof structures have greater weight and dimensions. The class of protection is also reflected in the cost. The higher the numbers, the more reliable the protection, the higher the price.

Choice for home wiring

Metal and plastic junction boxes for hidden wiring

The junction box for hidden and open wiring is selected depending on the type of line to be installed.

  • For external wires, it is required to use overhead branch structures (they are mounted directly on the wall surface).
  • If the wiring is hidden, recessed models are required for wall mounting.

For home use, it is not at all necessary to purchase modifications with a high protection class. A completely sealed structure may be required if it will be installed near a house on the street.

Most modern models are equipped with special terminals, which greatly simplify the installation process. There are also boxes equipped with a fuse, which, in the event of a short circuit, in an emergency order, cuts off the power supply. An additional advantage is that the cost is negligible when equipped with terminals and clamps.

When choosing, you need to analyze the material from which the wall is made, since the method of fastening will depend on this. In a concrete wall or brick, the boxes are mounted on a mortar, for plasterboard walls special fasteners are provided.

Better to give preference to proven brands. The cost is generally higher, but the build quality is more reliable.

Junction box installation

Installing the box in drywall

During the installation of an electrical installation, it is better to follow all the public and private rules. Wire lines, as a rule, run at a height or under the ceiling, therefore, the boxes are mounted in the same place so as not to waste extra meters of expensive cable. However, it is important to provide free access to the structure in case of abnormal or emergency situations.

If the electrical wiring runs in the space between the stretch ceiling and the base of the wall, the boxes must be placed below the level of the false ceiling. The ends of the conductive cores must be brought down. This may cause its own difficulties, but in the future, during repair and maintenance, it will be much easier to complete the tasks.

After installation, it is important that the integrity of the structure is not compromised. The lid should close tightly and securely, it is not necessary to clog the inner space with wires, it is better to install a new large box or another one next to it.

Modernization, maintenance and repair of wiring is impossible without opening the branch boxes, therefore, when laying the wiring, it is important to draw up a correct diagram, which indicates the number and location of electrical installation structures, how many lines they include. First of all, this applies to devices designed for hidden wiring.

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