We should pay attention to the following points when purchasing solar water heaters for domestic use:
1. In the thermal performance index, the higher the "average daily efficiency" is, the better the "average heat loss coefficient" is.
2. The key component of the domestic solar water heater is the all glass vacuum solar collector tube (referred to as the vacuum tube). The quality of the vacuum tube directly affects the performance of the whole domestic solar water heater. The coating on the glass tube inside the vacuum tube shall be carefully observed during purchase. This coating is called solar selective absorption coating. Due to the different manufacturing processes of various manufacturers, the coating color will be different, but generally it is black, dark blue or dark gray. The coating with good quality has uniform color, and the film layer has no scratch, peeling or falling off. There is no stone or nodule on the glass, so it is supported The supporting parts of the inner glass tube shall be placed correctly and not loose.
3. Pay attention to the pipe spacing between the vacuum pipes when purchasing. Generally, the center distance between the two pipes is about 70mm.
4. The support design of domestic solar water heater shall be reasonable, with sufficient strength and rigidity (supplement: corrosion resistance, do not use the support to fall down in two years) to ensure that it has enough bearing capacity. In some areas with large daily wind, especially in coastal areas, when purchasing domestic solar water heaters, attention should also be paid to whether the product has wind resistance in design.
5. In the current market, there are many kinds of reflectors for domestic solar water heaters, such as plane reflectors, curved reflectors, embossed aluminum plates, etc. when purchasing, it should be noted whether the reflector design of the product can make full use of the heat absorption surface of the vacuum pipe, and whether the vacuum pipe can receive the maximum light. (add: now most of them don't have reflectors. Businesses have saved costs and users' products have improved their wind resistance. Don't forget it.)
6. When purchasing, the number of permanent residents in the home shall be considered to determine the water capacity of the solar water heater. Generally, the standard of 40 liters per person is appropriate. In addition, the nominal water capacity of many products is calculated by adding the capacity of each vacuum pipe and the tank capacity of the water tank, but in fact, the water below the water outlet of the water heater and in the vacuum pipe cannot be discharged for use. The water users can really use is only the water between the water inlet and the overflow port. Therefore, when purchasing, they should ask the seller clearly what they have nominal water capacity Water capacity refers to the total water capacity or the actual water capacity that can be used, and the difference between the two.
7. If the purchased domestic solar water heater needs to be equipped with electric heating device, the product with electrical safety design shall be selected. It's better to sell it together with solar energy, so it's safer.
8. Purchase other relevant accessories, such as automatic water supply device, water temperature and water level indicator, solenoid valve, etc. the selection of these devices should be cautious. Some functions seem to be advanced, but there are too many components and reliability is not high. As time goes on, it is easy to have problems. When selecting, it is necessary to ask about the service life and warranty period. (supplement: try to let the merchant install an overflow pipe and a manual water filling valve (for standby), so that the microcomputer of automatic water filling can be used normally in case of damage or failure in the future,
9. After purchasing a domestic solar water heater, pay attention to whether the bracket is firmly installed, whether all screws and joints are tightened, whether the installation position of the upper and lower water pipes is reasonable, whether the water heater itself has reinforcement measures, etc. during the installation process. In addition, a check device must be installed in the water supply pipeline to prevent the hot water from flowing back into the cold water pipeline. (supplement: after the solar energy enters the house, a main hot water valve must be added for easy maintenance)
10. After sales service of domestic solar water heater is also very important. It's better to choose well-known brand products and distributors with good after-sales service. Because the domestic solar water heater is a durable consumer product, and is usually installed on the roof, once there is a fault, it is difficult for users to solve it by themselves, so after-sales service must be guaranteed.
11. Because the domestic solar water heater is installed outdoors and used for a long time, the vacuum pipe will be polluted by dust or impurities, thus reducing the heat absorption efficiency. Therefore, the vacuum pipe of the water heater should be cleaned regularly, especially in the snowy area in winter, it needs to be cleaned in time after snowing.