There is an opinion that lightning protection of a metal roof is not required. But at the same time, the supervisory authorities require that torso or pin lightning rods be used.
This is not a delusion. The roof itself is used as a lightning receiver, while all elements that protrude and are not metal must have a lightning rod.
True, this does not give a 100 percent guarantee. Of course, a metal roof serves as a lightning receiver, only in this case it must have reliable electrical contact over the entire surface.
That is, down conductors and lightning rods must be welded with grounding conductors, and in the event that it is impossible to carry out welding work, they must be connected using bolts.
To your attention! Between the sheets or metal tiles, there must be a normalized electrical connection.
Also metal roof, as well as elite copper roof, which will be a lightning rod, must be securely attached to the rafters. According to statistics, a direct lightning strike on the roof can cause a fire due to the fact that the metal flooring heats up to a higher temperature than the ignition temperature of the truss system made of wood.
In fact, most often, the metal tile is laid on a wooden crate, or on roofing material.
Of course, this is more profitable from an economic point of view, but not very safe. Very often, with a direct lightning strike into the roof, melting and burns are formed.
There are cases when lightning hit the roof, the thickness of the roofing material of which was less than 1 mm, while the formation of melting occurred, which caused the ignition of the insulating material, which led to fires.
Thanks to all of the above, we can conclude that if the connection of metal sheets is reliable, and there is an electrical connection between them and at the same time they are attached to non-combustible materials, then the roof can be attributed to lightning rods, of course, that the thickness of the sheets is not taken into account.
Tip! An alternative way is to ground the metal roof along with the installation of cable or rod metal receivers.
Let's take a closer look at the device of lightning rods:
- Do-it-yourself lightning protection
It is desirable that all buildings have a lightning rod to protect the house from fire and save radio and electrical appliances. The lightning rod system is represented by several parts: external and internal protection of the house.
The internal protection is designed to protect the electrical network from overvoltage due to a lightning strike, and the external protection is designed to protect against a direct strike.
The external system is represented by a lightning rod, down conductor and a device designed for grounding. Any metal pin or cone can be used as a lightning rod.
The internal system involves the use of special discharge devices for electrical networks that limit the voltage
You cannot make an internal lightning protection system yourself, however, you can integrate ready-made devices into the power grid. The simplest and cheapest way of internal lightning protection is to turn off all electrical devices in the house if lightning follows thunder in less than 10 seconds.
External lightning protection can be easily done on your own in a short time. In addition to the lightning rod, down conductor and ground electrode, you will need a welding machine and clamps or brackets for connecting down conductors, made of soft metal.
A current collector is connected to the rod metal receiver, which is made of an iron wire having a circular cross section. This down conductor combines a grounding point and a lightning rod.
The ground electrode can be made from a strip of metal having a cross section of at least 150 sq. mm. For example, a steel bar having a diameter of at least 18 mm can be used. All elements are interconnected by electric welding or metal clamps with nuts and bolts.
Grounding must be done at a distance of 1-1.5 meters from the dwelling. At what height to place the lightning rod will depend on the angle of protection, which is approximately equal to 70 degrees.
The highest point of the lightning rod should be made like the top of an umbrella. In order to protect the lightning rod from unforeseen situations, an additional lightning rod can be installed above it.
- How to make grounding?
Grounding should be carried out from a metal object, which will have the largest possible area, and be buried to the maximum depth. As a ground electrode, you can use a metal corner, a thick pipe, etc.
It should be buried to a depth exceeding the depth of freezing of the soil. It is advisable to dig a reinforcing mesh made of thick wire, a thick metal barrel or iron into the ground.
During a drought, the current does not pass well into the ground, so it is recommended to keep the ground moist at the ground. This can be done by draining water from the roofs, connected to the ground, or by pouring water from time to time onto the ground.
Also, in order to improve the electrical conductivity, it is possible to drill shafts every few years and place saltpeter or salt in them.
- How to make lightning protection?
In principle, lightning protection is a bare conductor that is protected from corrosion. It is usually made of copper wire, aluminum or galvanized steel.
It is believed that a lightning rod is able to protect a certain cone from a lightning strike, which depends on the side surface and its own top.
Therefore, on how high you raise the lightning rod, it will depend on what area it will be able to protect. If you place it at a height of 10 meters, then the cone will end 10 meters from the lightning rod.
It is desirable that there is a large tree near the house. Then the lightning rod can be fixed on a pole, which will be fixed on a tree with the help of clamps. It will be necessary to raise the lightning rod higher than the top of the tree.
In the event that there is no tree, then the lightning rod can be combined with a television mast. If the mast is made of metal and not painted, then it will become a good lightning rod.
If the mast is made of wood, then a wire or bare wire must be run along it, after which this wire must be connected to ground.
If you are not at all lucky, and you do not have a large tree or a TV mast, then the lightning rod will need to be installed on the chimney. To do this, a metal pin is attached to the pipe, which is connected to ground.
The only thing to consider in this case is that the pin will create a wind load, so it will be possible to damage the pipe if it is weak.
In this case, lightning protection is carried out as follows: Masts of 1.5-2 meters are installed on the gables. A thick wire with insulation is pulled between them.The wire is connected to ground. This method will create a protective zone for the house.
- How to calculate lightning protection
The process of calculating lightning protection is quite difficult, however, recently a large number of free calculators have appeared that can calculate everything.
To calculate passive protection, you need to know what type of protected building belongs to - a rectangular building with a given height, length and width, a linearly extended object or a single rod structure.
Next, you need to know the number of annual thunderstorms, which determines the approximate number of lightning strikes per square kilometer. This is reflected in a special map. Having received these values, you can easily calculate lightning protection.
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