In the method shown in the middle, downlead 1 and downlead 2 do not form a smooth electrical path.
During the connection of lightning protection grounding reinforcement of hybrid foundation, the ground beam surface reinforcement and pile reinforcement must form a good equipotential.
The connection conditions are shown in the figure below, both of which can be used.
In addition to equipotential bonding according to the connection method of two downleads in the same column, the connection method between the two gluten bars and the downlead is also very particular.
Welding between downlead and foundation reinforcement.
At the same time, it can also facilitate the rapid discharge of lightning current, Therefore, a smooth electrical path must be formed when the lightning strip is connected with the downlead (the standard connection method is shown in the figure below).
In the connection method shown in the figure below, the lightning current generated on the ring beam can smoothly flow into the grounding device through the down lead.
The connection shall be as shown in the figure below.
Sometimes, in order to save materials, it can be connected to the pile reinforcement through the cushion cap reinforcement.
The lightning protection design code strictly stipulates the connection size of reinforcement, that is, double-sided welding is greater than or equal to 6D, and all reinforcement are required to be connected into electrical path.
Smooth current path shall be formed during connection.
In addition to the reliable connection of the strip foundation surface reinforcement, the downlead shall also be connected with the pile reinforcement through the surface reinforcement or directly.
In general, the independent strip foundation mainly uses two outer gluten bars as lightning protection grounding body, and the equipotential between the gluten bars shall be connected in the way of down lead equipotential.
When the connection is not correct, residual lightning flows into the sanitary room, causing the safety of personnel and equipment.
If the following connection method is adopted, the lightning current generated on the ring beam cannot flow smoothly into the grounding body, and part of the lightning current on the down lead can flow smoothly to the ring beam, resulting in lightning current on the metal doors and windows and aggravating the risk of lightning stroke, so it should not be used as far as possible.
The common misconceptions about the connection between the lightning strip and the downlead are mainly as shown in the figure.
In order to make the potential between the two column bars equal, in addition to spot welding or binding between the stirrup and the column bar, the reliable connection between the two columns is also very important.
There are three common connection misunderstandings of downlead in the same column, as shown in the figure below.
In order to achieve the proper discharge effect, the equipotential of the toilet shall be reliably connected with the down lead nearby.
The method shown on the far left adopts U-shaped welding of reinforcement, and some lightning current flows from down lead 1 to down lead 2, but no smooth electrical path is formed with the grounding device.
Modern buildings often use their own reinforcement as lightning protection devices, such as ring beam reinforcement as grading ring, column reinforcement as downlead, foundation reinforcement as grounding device, etc.
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However, in the actual detection process, most constructors often have some non-standard construction phenomena on the problem of reinforcement connection.
Connection of equipotential and down lead in toilet with the increase of household appliances, in addition to making grounding wires on sockets, most buildings have made equipotential bus grounding devices in indoor toilets due to safety needs.
During the connection, pay attention to the smooth current path to prevent the ground potential counterattack caused by wrong reinforcement connection.
Correct practice: two column bars (two column bars on the opposite corner or on the outer side) are commonly used as the building downlead in the same column.
When the lightning current hitting the lightning strip is discharged in one direction, the discharge is smooth due to the connection radian > 90 °, while the lightning current in the other direction seems to cause poor discharge due to the connection radian < 90 °.
The connection mode makes the leakage current generated at the equipotential not form a smooth electrical path with the down lead nearby.
Generally, the outer ring beam reinforcement used as lightning protection device is mainly two gluten bars on the outside.
When lightning strikes the lightning strip, most of the lightning current will be discharged to the earth along the downlead nearby, and the lightning current belongs to instantaneous current and has great impact.
The common connection errors are mainly as shown in the figure.
The connection between downlead and foundation reinforcement is divided into two cases: the connection between downlead and strip foundation reinforcement and the connection between downlead and hybrid Foundation (strip foundation and pile foundation) reinforcement.
Some construction personnel are for the convenience of construction.
The lightning current through one down lead can flow smoothly to the other down lead, and the two down leads can truly realize equipotential.
Welding between the outer ring beam used as the grading ring and the down lead in some high-rise buildings, the reinforcement of the outer ring beam is used as the lightning protection device or grading ring, so that the lightning current generated on the metal doors and windows can flow to the down lead through the ring beam.
In the connection method shown on the right, a smooth electrical path is formed when lightning current flows from down lead 1 to down lead 2, and no smooth electrical path is formed when lightning current flows from down lead 2 to down lead 1.
The connection is shown in the figure below.
The welding between downleads in the same column uses the building column reinforcement as the downlead, which can not only save materials, but also not affect the beauty of the building.
The construction method on the left is slightly more difficult, and the construction on the right is relatively simple.
According to the principle of inductance, the bending radian of the discharge path at the bending part shall be greater than 90 ° to avoid large inductive reactance.
The equipotential connection of the toilet mainly pays attention to the leakage current to form a smooth discharge path.
