Home improvement lightning protection is described in accordance with RD 34.21.122.The rest is fiction. Do I need lightning protection in a private house? Decide on your own, if an antenna is hit in the antenna, the closest standing electronics will burn: home theater, receiver or TV.Satellite dish converters are burning - as lucky. Grounding does not hurt. By the rules it is joined by lightning protection. The two contours mentioned are closely related, but it is logical to start with weather protection, the load is guaranteed to arise, and considerable.
How to equip lightning protection
The height of the lightning rod is clear. Beats in the highest point, you need to put higher. We offer to start in order.
According to RD 34.21.122, houses are divided into three categories of lightning protection. For example, single buildings with a height of over 30 meters fall into category three. At the same time, two types of lightning protection zones are distinguished. These data need to be determined for their own structure once( for example, IIIB), then used to determine the necessary parameters.
You need to understand how to perform lightning protection. Please note that the potential equalization system is being discussed at the same time. Finally, it is stipulated for certain types of buildings that it is possible to carry out a simple connection of communications to the grounding system( class II and III, if most of the premises do not need protection).For example, a residential house category IIIB.Communications overground. Go to the section Lightning protection category III( paragraph 2, RD 34.12.122).
rules In accordance with the necessary section, we are referred to the subtitle "Lightning protection category II in compliance with two rules."First, wherever possible, the contour is connected to the reinforcement of the foundation. A prerequisite is the welding of reinforcement between the plates.
Secondly, the steel tire is laid no closer than 3 meters from any entrance or in a place isolated from accidental access by people. For an individual, this is not feasible, a project will be required to finalize the facade, but there is no talk about installing lightning protection. The tire is a steel strip( not less than 40 x 4 mm), which goes down along the wall directly into the basement, to grounded structures.
Also includes metal parts, for example, fire escapes. A separate lightning conductor will not be a way out of the situation, but the owners of private households are allowed to think about this option.
It's time to choose the design of lightning protection. Receivers are made in the form of metal rods or cable. In the latter case, there are a number of pins connected by means of joining a steel cable, and there are at least two tokovodov. It is logical - one at the ends of the network. If the slope of the roof is not too large( 1 to 8), apply a protective mesh of steel.
Specific parameters are selected for these methods. For example, it is indicated that, in the presence of a pipe, it is covered by a zone of lightning protection with a margin of 5 meters radius. To satisfy this requirement, we will look at Appendix 3. It turns out that a single rod of steel detects a zone of protection against lightning in the form of a cone, less than its height. The formulas for the calculation are given, it is easy to determine whether the pipes mentioned above fit into the proposed volume: ho =( 0.85 - 1.7x0.001( h - 150)) h. For a rod three hundred meters, the height of the cone is 178.5 meters. We are interested in more modest size. Height is determined by the simplest formula: hо = 0.85 h. The radii are for the first and second cases, respectively, rо =( 0.8 - 1.8 x 0.001( h - 150)) h and ro =( 1.1 - 0.002 h) h. There are two zones, A and B, the authors gave formulas for the first. These letters define the type considered at the beginning of the table. In the described example - IIIА.
Approximate calculation is already possible to do. Lightning at home in the form of a conventional pin on one end of the ridge clearly will not save. The approximate radius of coverage at a height of 3 meters will be slightly more than the proposed three meters. It is better to mount the pin in the middle of the skate, not on the edge. More suitable cable scheme. Two rods are taken along the edges of the ridge, and then the construction is combined with a tensioned cable( the height above the roof is at least 25 cm).Good news: if the length of the ridge is less than 10 meters, it is permissible to perform the grounding conductor and the current lead from the only side.
The double tap has a protection zone that is similar in shape to the stadium. Anyone will be able to write formulas from RD 34.21.122.It is permissible to use two pins, but the connection with the cable looks more reliable. It turns out a clean oval, there is no danger that part of the roof will be released from guardianship. The pins are taken of different heights, the situation is also described by the standard.
In the future, it is easy to add a lightning protection device, covering important objects:
- weather vane.
With the dimensions figured out, time to go over to the little things: consider the main dimensions of roof lightning protection.
Dimensions of the components of lightning protection
The project of lightning protection without dimensions and sections of reinforcement is cheap. Grounding is recommended to perform on the basis of reinforced concrete structures, already mentioned. The armature of all the plates is welded reliably, then it serves as a way to divert electricity to the ground. If it is impossible to fulfill the specified condition( resistance is high or others), typical ground loops should be used.
According to the rules, they are exclusively made of smooth round reinforcement( without corrugation) with a diameter of at least 18 mm. The rods are combined with a steel tire 40 mm wide and 4 mm thick. Similar goes down from the roof. According to the rules, the length of the welds is at least 10 cm. The design differs by the parameters:
- The diameter of the pins;
- Pin Length;
- Underground circuit;
- Contour depth;
- Overhead Loop;
- Exalted tokovod.
pins Armature pins with a diameter of 18 mm are driven into the ground( half a meter deep in the bottom of the trench) at least 2.5 meters. The distance is provided within 2.5 meters. Practitioners advise taking pins with a margin, preferably 3 meters. Then the lightning protection and grounding will unite into a coherent whole, including the potential equalization system. The pins are the easiest to hammer using a punch. This is a big drill, the spindle performs its reciprocating blows. For fixing the rod, a crown is used for a brick of 40 mm( the method of Roman Rostovchanin, see Youtube).The diameter is chosen from those considerations that the tip of the reinforcement will slowly flatten itself, with other sizes it will simply clamp. The rod for better entry is lubricated( for example, grease).So lightning protection of houses and apartments is equipped much faster.
The length of the pins
The pin was not chosen for nothing longer than necessary. In process of driving, the piece of iron bends, especially the end on which the perforator knocks. Under the device of lightning protection of buildings, you need to stock up on a welding machine, other connections under the ground will not last long. The upper end of the rod should be bent 10 cm to get a good seam. Cooked on both sides. The ends of the tape are allowed to bend, therefore, the extreme pins do not need to bend. Sometimes they try to use a corner instead of round fittings. In this case, the shelf is provided in the size of 40 - 45 cm. Such things are difficult to hammer into the ground, the above method is not suitable. The end of the steel should be chamfered: when sawing with a grinder, hold at a 45 degree angle to the valve axis. In this case, the lightning protection system is enough for the whole house. In practice, it is possible to use fittings with a diameter of 14 mm for private households( due to reduced requirements).
The underground part should not be painted, with the exception of welds where the steel overheats and loses its protective properties. Lightning is usually covered in black( according to the rules).The remaining parts are free to come into contact with the ground. If there are metal constructions like arbors on the backyard plot, they are combined with the contour with the help of wire rod( thin steel bar, sold by hanks) for 6 - 8 mm. Joints are boiled according to the given example.
Depth of the contour
The depth of the steel strip joining the rods is half a meter. There is no need to dig deeper, so that the lightning protection of the bath doesn’t get to the groundwater, and less - it will get oxygen, and the electrical contact is unimportant. As a lightning protection, it is possible to use a steel roof: a horizontal conductor( tape) is dug along the perimeter of the building, to which vertical pins are welded to the corners, extending deep into the ground( see above requirements).The technique is suitable when using the grid.
The instruction for lightning protection is incomplete without a description of the aerial part. The general technique is partially given above, it is shown where to get the rest of the data. Now let's see what the standard says about the materials. The dimensions of the rods of the underground part are taken from table 3. According to the norms, the minimum diameter is 10 mm, but in practice it is not possible to hammer such a thing into the ground. The cross section of the strip is chosen not less than 160 square millimeters with a thickness of not less than 4 mm. The size of the tokovods in the air( reaching along the wall) is more modest: 48 square millimeters. With a thickness of 4 mm - width 12. About the round tokovodov aboveground parts have already been said when they mentioned the rod of 6 mm in diameter. The diameter of the lightning rods itself is selected based on the mechanical strength conditions, is not allowed less than indicated in Table 3.
The instructions for lightning protection of buildings above which trees are rising are considered to be very curious. In this case, a tokovod is protruded along the trunk, projecting above the crown's top point of at least 200 mm.
What is active lightning protection?
Most experts agree that active lightning protection is a myth. The idea is to create an ionization layer around the spike of the lightning rod. In this case, allegedly the conductivity of the site increases, it will be possible to significantly reduce the height of the structure. For ionization, different methods are used, from the emission of radioactive metals to the waves of the communication range.
How the lightning protection of the active type is checked remains unclear. Otherwise, the technique would have won many supporters long ago. Lightning protection of buildings according to the described type has not yet been fully investigated, there are enough skeptics to criticize such undertakings. RD 34.21.122, of course, keeps quiet about the structures described. Perhaps tomorrow, the lightning protection of the facilities will be created exclusively according to the active type.