If we compare the type of installation of electrical wiring that is open and hidden in the thickness of the wall, then from the point of view of fire and electrical safety, the second is more preferable. Once made and forgotten, as its accidental damage is practically excluded. Nevertheless, in some cases it is necessary to carry out the wiring using the open method. For example, in a room made of logs or beams, it’s rather expensive to hide the wire in the wall. An excellent solution are boxes for electrical wiring. Even a beginner home master will cope with their installation.
What are the boxes for electrical wiring
Imagine that you need to perform a network wiring in a room, but you cannot embed a cable into the walls.
Power wiring, made openly on insulators, from the point of view of appearance does not fit into every interior. If the wire is hidden in a corrugated pipe, then it is also not too beautiful, and is more suitable for utility rooms and industries. However, there is a way out - this is a box for electrical wiring. They are a special profile with a section in the form of the letter "P" made of plastic, aluminum or galvanized metal. In one way or another, it is fixed on the surface, cable-conductor products are laid in it, and the box is closed with a lid on top, which is held by latches. Boxes for electrical wiring are implemented with standard “sticks” 2 m long. Regardless of the material, this design does not support combustion.
Note that in addition to the simplest U-shaped section, there are more complicated modifications in the form of "". That is, having completed the installation of boxes for electrical wiring, during installation, you can divide the lines by laying them in separate sections of a single design. In this case, the covers can be separate.
How to choose a cable box
The most inexpensive solutions are modifications made of plastic. In addition, compared to metal, they are easier to fit during installation. A plastic wiring box has another advantage - in case of damage to the cable insulation, the dangerous potential cannot spread along the surface.
When buying, it is very important to choose the right amount of box. Usually, the pre-measured footage must be exceeded by 10-20%, because otherwise there may be a situation where the acquired box is not enough and you have to look for an additive somewhere. There are also related accessories on sale: turns, corners, tees, allowing you to give a finished look to the wiring. These items must also be purchased. Particular attention is required to the box for electrical wiring under a tree, because if there is a lack of any structural elements, it is almost impossible to choose the exact same ones at another outlet due to differences in color scheme.
Before going to the store
We recommend using the following algorithm of actions prior to the direct purchase:
- to think over the installation locations of sockets, switches, fixtures and other consumers, as well as their number;
- draw a wiring diagram for the premises;
- determine the required footage - stock is required;
- provide fittings (turns, external and internal corners, junction boxes);
- take into account the dimensions of the boxes for electrical wiring and choose the most suitable depending on the type of cable used; in addition, the dimensions are also affected by the number of sections in the product;
- decide how fixation on the surface will be carried out, stock up with the necessary tools;
- think about whether metal boxes are needed for wiring or whether plastic options can be dispensed with. The undoubted advantage of the iron trays is their strength. They can even lay high-voltage cable. A ground contact is provided. Plastic box for electrical wiring still does not allow to place a large number of cable-conductor products, as it either starts to bend, or requires too frequent fastenings to the base.
Locks and material
The latches holding the cover can be placed on both two and one sides. In the latter case, a special groove is provided instead of the latch. Bilateral fixation is more reliable, so it is better to choose such models. The “disease” of the products of some manufacturers is the unreliable fastening of the lid, which is why you have to tap on it a little to close it.
Here the problems begin: depending on the plastic used, the boxes are often deformed (burst, bend, etc.). Therefore, when buying, it is very important to try to close the selected model, and not to solve unusual tasks during installation. So, there were cases when, at the final stage of laying, the lid at the points had to be “put on glue”. Metal boxes for electrical wiring in this regard are much better than plastic ones.
Dimensions
Let's consider in more detail what are plastic boxes for electrical wiring. Their sizes are as follows: 22 × 10 mm - 40 × 16 mm (conditionally called mini-channels); 12 × 7 mm - 16 × 12 mm (microchannels); 100 × 40 mm - 100 × 50 mm (the most common standard); up to 200 × 80 mm (large). There is a technique that allows you to accurately determine the desired size. To do this, use the formula:
S = (N × d2) / K,
where S is the required cross-section of the box, mm.kv .; N - the planned number of cable routes, pcs; d is the diameter of the cable, mm; K - correction factor, the use of which is necessary in order to prevent too tight packing (0.45).
Having received the result, you must select the nearest box of the appropriate size. When choosing plastic boxes for electrical wiring, the dimensions of which are smaller than the required (calculated) ones, it is important to understand that the temperature conditions of the cable cores will be violated, and the lid may loosely lock and fly off if you accidentally touch such a tray.
Installation
Having measured the strip of the desired length, make a mark on the box and cut it with a hacksaw for metal (regardless of material), a sharp mounting knife or even side cutters. This operation should be performed on an assembled box, including a tray and a closed lid. The transition "wall-to-wall" or "wall-to-ceiling" is best done using special corners.
If they are not, then in not very noticeable places they sometimes use a special technique: on one tray they cut the base, and on the other - the lid, and combine them. True, a right angle in this way can only be obtained if a cover material resistant to fracture is used.
A mark is drawn on the surface with a simple pencil, indicating the future location of the box. It is recommended to use a level and a plumb line. On even surfaces, the box can be glued with liquid nails, however, further work is possible only after complete drying. The easiest way to fix the tray to the wooden wall is with self-tapping screws and a cordless screwdriver. Brick and concrete foundations require a different approach: holes (2-3 mm) are made in the bottom of the tray every 0.5 m. Next, the box is applied at the marked level to the wall and marks are placed through the holes. In them, using a percussion drill or perforator, channels under the dowels are drilled. Further installation consists in fastening with screws.
In principle, there is nothing complicated in the installation of cable ducts, and this work is beyond the power of even an unprepared person. The main thing is not to rush anywhere, carefully measure and think through everything. Especially if the work is done for the first time.
Cable production
Sometimes it is very difficult to perform such a simple task as laying a cable route in a box. The line bends, “snakes”, props the lid from the inside, etc. The cables whose wires are made of rigid single conductors are especially “famous”.
Therefore, they must be carefully aligned and bent. In addition, some boxes have additional longitudinal partitions, simplifying the laying of such "naughty" conductors. The easiest way is to stretch all the lines at once and, as they are laid, close each covered meter with a lid. The technique described by us above will help reduce the noticeability of joints: trimming trays and covers so that these lines do not coincide.
Recommended Placements
The PUE Guide does not impose any requirements on the location of sockets, switches, fixtures and the way of orienting cable routes. However, it is considered an unwritten rule to draw lines horizontally and vertically, avoiding curves. In the case of hidden wiring, this simplifies the search for the place of damage, and the external boxes look more aesthetically pleasing. The distance from the ceiling to the track should be 150 mm, and a distance of 100 mm is necessary from the window and the doorway . And, of course, intermediate junction boxes on the line should be provided, which will help restore the efficiency of the lines if necessary.
General tips
Since the distances between the walls at the ceiling and the floor often vary due to the peculiarities of domestic construction, you should not cut off the cable duct for top installation, taking measurements below. In addition, the angles may seem right only from the side, and when you try to install a transition angle, it turns out that this is not so. Performing the transition of the route through the wall, you need to place a tube there (metal-plastic is suitable) in order to be able to replace the site or "stretch" the route. All these nuances must be taken into account.