Lightning protection of a metal roof - device and
Since ancient times, the thunderstorm was for people a terrible, incomprehensible natural phenomenon that scared and carried the danger of fire and even death. Therefore, for a long time, lightning was considered the punishment that the gods sent to punish sinners. Now the nature of the occurrence of thunderstorms has been thoroughly studied and familiar even by a schoolboy, although she did not become less dangerous.
To prevent fires as a result of lightning strikes, lightning protection of a private house is organized on the roof. In this article we will discuss the most effective measures of protection against lightning, which are necessary for each building.
The need for lightning protection
Many people in the construction of their own residential or country house do not think about how the roof lightning protection works. A common misconception is that metal roofing types do not need protection from lightning strikes, although this opinion is a big mistake. For a residential or non-residential building, whatever the roof covering, the main hazards consider:
- Direct lightning strikes. Lightning protection of the pitched roof is a guarantee of safe operation of any house, since the ridge is, as a rule, the highest point in the district, which attracts lightning strikes. Even if a non-flammable coating is laid on the roof, there is a danger of fire if a charge gets in, since the roof frame is made of highly flammable wood.
- Static electricity. The roofs of metal tiles and other metal roofing materials accumulate static electricity well, which occurs when friction of small particles of dust on the floor. The accumulated voltage can give a discharge if the person standing on the ground or a ladder accidentally touches the roof surface of a building with a metal roof, which can lead to serious injuries.
Important! Experienced roofing masters believe that roof lightning is an indispensable element of the structure regardless of the shape of the roof and the type of roofing material used to cover it.
Device
Lightning protection of the roof of metal tiles or any other roofing material - a set of measures to ensure the safe operation of the building during a thunderstorm and to prevent injuries during the maintenance of the roof due to the discharge of static electricity. In addition, the presence of a well-designed and installed lightning protection is an additional protection of electrical equipment installed in the house from power surges. It consists of the following components:
- Lightning rod. A lightning trap is a conductor that encounters a lightning bolt on the roof. It is a pin, cable or special mesh. Fastening of the lightning rod should be carried out at the highest point of the roof - on a ridge, chimney or ventilation pipe. If the roof has a complex structure or a large area, then for the effective operation of lightning protection the lightning conductor needs not one, but several at once.
- Current lead The lightning protection device of the house must include a current drain, which takes a safe route away from the electrical conductor to the grounding conductor. It is made of reliable and durable steel wire with a minimum thickness of 6 mm.
- Grounding conductor. Houses with a metal roof should be equipped not only with an air-termination box and a down-conductor, but also with a grounding conductor. The earthing switch is a special device that connects to the down-conductor, it is necessary so that the discharge of electric charge takes place in the ground. As a grounding conductor, a structure welded from metal angles or pipes, having a sufficiently large area of contact with the soil, is used.
Note! To determine which lightning protection of a metal roof is required, a simple rule is used: it is believed that one lightning rod protects a cone from lightning, the top of which is on its top, and the sides diverge at 45 degrees from it.
Installation of lightning protection
Lightning protection of a flat roof or a pitched roof construction is made during the installation of the roof or already during the operation of the building. It is important to correctly calculate the number of interception rods and the contact area of the grounding conductor so that protection against electrical discharges works effectively. It is believed that the higher the lightning rod, the greater the area that it protects from lightning strikes. It is necessary that this safe area included not only a dwelling house, but also necessary outbuildings. When installing lightning protection, you must consider the following requirements:
- The lightning rod is installed on the highest point of the roof. Usually, the installation is performed on a skate, on a television mast, chimney or ventilation pipe. The disadvantage of this method of installation is that the high metal spire creates an additional wind load, and can also be deformed. An alternative installation site can be a tall tree located near the house.
- Connect the ground receiver with a grounding conductor. For its manufacture using steel wire with a thickness of at least 6 mm, which must withstand voltages up to 200,000 amperes. The current lead is laid along the shortest path, and the welding between it and the interception rod must be very strong so that it does not collapse under voltage. From the lightning rod, the down-conductor is lowered first along the roof, and then along the walls of the building at the maximum distance from the windows and doors. It must be securely fastened to the walls with metal clamps.
- Grounding switches are made of stainless steel or copper, as they have good conductivity. It is buried in the ground to a depth of at least 2-3 meters at a distance of more than 5 meters from the driveways to the house, porch, blind area. The soil at the site of the earthing should be loamy or clay, wet. Before a thunderstorm, you can even specially moisten the soil if it is sandy and does not hold water well.
Remember! Lightning protection needs regular maintenance to keep it working. It is recommended to inspect the air terminal annually, carefully checking its attachment points to the down-conductor. Once every three years, weakened contacts should be replaced or strengthened, and once every 5 years, you need to dig up a grounding conductor and check the depth of its corrosion. If the grounding element has rusted by more than a third, then it should be replaced.
