Most of the solar water heaters are installed on the roof, and their height is generally higher than the lightning protection belt of the building, and they are susceptible to the double damage of direct lightning and induced lightning, and there are great hidden dangers of lightning protection. Therefore, comprehensive lightning protection measures (including the installation of suitable surge protectors/surge protectors) are required.
The first is the direct lightning protection measures for solar water heaters
The outdoor components of solar water heaters mainly include water tanks and metal brackets, which are usually installed later, generally exceeding the height of the lightning protection belt, and are located in the direct lightning zone (LPZOA zone), which is prone to direct lightning strikes. Direct lightning protection measures are to make the external parts of the solar water heater within the protection range of direct lightning strikes.
The direct lightning system mainly includes three parts: lightning receptor, down conductor and grounding device.
When installing an independent lightning rod, there should be a distance of 2 to 3 meters between the independent lightning rod and the solar water heater. The rolling ball method is used to calculate the height of the lightning rod to protect the solar water heater. In addition, the metal of the water heater should be grounded, and its transition resistance should be less than 0.03Ω, and there should be at least two welding connections with the roof lightning protection device to ensure the possibility of lightning current discharge during a possible lightning strike.
(2) lead down
The down conductor layout is generally set according to the number of lightning rods. One lightning rod is equipped with one down conductor, and the down conductor is installed in an open laying method. The down conductor should be protected by insulating material at a distance of 2 meters from the ground to prevent people from touching it. Thunder strikes back the accident.
When an independent down conductor is set, there should be a certain distance from the independent down conductor of the lightning rod to prevent lightning strikes to the independent lightning rod or lightning belt, strong lightning current or induced lightning current is introduced into the solar water heater, or along the water pipe, electric heating Lines etc. enter the room, damaging the indoor electrical equipment and even causing personal injury.
The independent lightning rod can share the grounding device with the direct lightning protection device of the building. If there is no common grounding device, an artificial grounding body shall be installed, and the grounding resistance shall be ≤10Ω.
The second is the lightning protection measures for solar water heating systems
(1) Power line protection
The water level and temperature controller of the solar water heater needs to be connected to the outdoor power line. If the lightning current enters the room along the power line, it will not only damage the water level and temperature controller, but also through the indoor wires. Side flashover may also hurt people indoors. Therefore, a power surge protector should be installed at the end of the power supply to effectively discharge the lightning current induced from the power line into the ground.
(2) Signal line protection
The signal lines of solar water heaters generally have water level sensors, temperature sensors and solenoid valves. These devices have relatively low operating voltages and are easily damaged by lightning. Therefore, it is necessary to carry out lightning protection on each external line, that is, install a signal surge protector. When selecting, choose a suitable signal surge protector with small insertion loss based on the specific parameters of the solar water heater.
(3) Electromagnetic shielding measures
The line from the roof of the solar water heater to the bathroom has auxiliary electric heating, water level, and water temperature lines. All of this part of the circuit must be shielded, and both ends of the shielding layer must be grounded. In the line from the solar water heater tank to the roof, a steel pipe is used. The upper end of the steel pipe is connected to the solar water heater bracket, and the lower end of the steel pipe is connected to the lightning protection belt on the roof to ensure the secondary shielding effect of the line.