Household air-cooled heat pump unit is widely recognized by high-end apartment and villa users a form of household central air conditioning, which is composed of air-cooled condensers, compressors and water refrigerant heat exchangers and other components. Water refrigerant heat exchanger is the refrigerant and water heat exchanger, resulting in frozen water or hot water, and then use the pump to chilled water or hot water to the fan coil, and then through the fan coil fan inside the coil of chilled water or heat Water cooling or heat blowing into the room, to meet the requirements of the room cooling or warming. The energy of the system is transferred from the refrigerant to the water (refrigerant) and the water is then diverted to the room air. Relative to the variable refrigerant system, there is a slight leak in somewhere in the piping system or a slight uneven distribution of water flow, which will not affect the operation of the unit. However, for a unit with variable refrigerant flow, At the existence of refrigerant leakage, uneven refrigerant distribution, pipeline congestion, poor return pipeline problems, the entire system will be paralyzed. As household air-cooled heat pump unit is a result of large-scale central air conditioning miniaturization, but in full accordance with the design and installation of large central air-conditioning is inappropriate, but must consider its target group is home users, it is impossible to have someone Management, so in the design process of chillers must implement maintenance-free and less maintenance design guidelines. At present, most of the sales and installation of residential central air-conditioners are the previous sales of household air-conditioners. Since the installation of residential central air-conditioners is totally different from that of household air-conditioners and large and medium-sized central air conditioners, many installers lack experience and, in addition, There is not much experience in the installation of sales and installation of units can not be well trained, chiller installation is often a lot of problems, the most serious is the heat exchanger frozen, the entire unit may be scrapped, but also face the claim risk. The main reason for the freezing of the water heat exchanger is that the water flow through the heat exchanger does not reach the minimum flow required for reliable operation of the unit. Ensuring that the correct flow of water to the heat exchanger is a necessary guarantee for the reliable operation of chillers can lead to icing of evaporator chillers (severe freezing), high condensing pressure, "biting" of compressors, etc. malfunction. In the event of these failures, the brand's quality reputation will be very much affected. Therefore, household water chillers water flow control and protection is very important, appropriate water flow detection methods and testing components to ensure that the unit only in the system water flow is greater than the minimum allowable water flow, to a large extent, to avoid air-conditioning host malfunction. 1 household heat pump unit connected to the design of the water pipe 1. 1 household heat pump water pipe material selection principle The main objective of the domestic heat pump water pipe design is in accordance with the maintenance-free and less maintenance design to select the appropriate water pipe material, if easy to adopt Rusted, fouled, and corroded pipes require users to perform annual maintenance at a fraction of the cost, while systems that use variable refrigerant flow do not need this cost. From the reliability of the operation of the water pipeline system, the appropriate water pipeline material will not be generated due to improper construction caused by the water filter or heat exchanger plugging and will not produce rust, corrosion and scaling of the water pipe affect the life of the unit Case. Although good pipe material to increase the cost of installation, but greatly reduce the cost of air conditioning unit maintenance and maintenance costs in the life of the comprehensive costs will be greatly reduced. 1. 2 household heat pump outside the principle of choice of the water pipe The heat pump unit outside the water pipe design should also be maintenance-free and less maintenance to choose the appropriate design of the water pipe, or although the unit within the selection of the appropriate water pipe material, but outside the unit Still using easy-to-rust, fouling and corrosion of the water pipe The entire water piping system can not achieve maintenance-free and less maintenance. I think the manufacturers in the household heat pump unit installation instructions should be made on the water pipe material to make it clear that what material is not allowed to use what material is recommended to use by the manufacturer's technical staff of distributors and installers for full training , Completely avoid the water system due to the impact of water pipe material blockage. Thus reducing the pipeline blockage caused by the water flow down freezing cold heat exchanger phenomenon. 1. 3 household heat pump water filter selection and installation Household heat pump water pipe diameter is generally relatively small (not more than DN65), the pipe between the pipe thread connection, if the use of reinforced plastic and other materials connected For hot melt or glue bonding. The purpose of selecting water filter is to filter out the impurities generated during the installation of the water pipeline and the exfoliation impurities such as scaling and corrosion caused by prolonged running of the water pipeline so as to prevent the impurities from entering the heat exchanger and if the impurities are very harmful to the heat exchanger once, Local heat exchanger may cause blockage. If the unit heat exchanger is brazed plate heat exchanger or bushing heat exchanger will be difficult to remove, because these two heat exchangers can not be mechanically cleaned only try to remove by way of recoil. If you can not effectively remove the impurities in the heat exchanger will result in water-side heat exchanger local water flow decreased, while the refrigerant side of the refrigerant flow remained substantially the same, there may be a gradual decline in water temperature even below the freezing point of water, due to blocked Due to the decrease of water flow, the side of refrigerant adjacent to it is not completely evaporated, and the frosting or even freezing of the gas return pipe occurs, which makes it easy for the compressor to produce liquid attack. If the heat exchanger is partially blocked to a lesser extent, the entire water flow of the system does not change much at this time and the water flow protection switch does not work. The frost protection sensor (inserted into the heat exchanger to detect the water temperature) also can not detect the minimum temperature, frost protection does not work, a terrible thing happened - heat exchanger frozen until the entire refrigeration system scrapped. In order to prevent the use of raw materials like galvanized pipe construction, hemp rope and other impurities blocking the heat exchanger in addition to standard construction during construction, the manufacturer of the chiller design process can also avoid this situation. Water filters are one of the two most critical components of a heat pump unit water system. The proper choice of water filter can effectively prevent impurities generated during the construction of water pipes into the heat exchanger. Proper water filter mesh number and form is very crucial, should be set aside to install the bypass unit inlet pipe valve, the installation is completed before commissioning bypass module unit heat exchanger for water pipeline cleaning. In this case, it is best to use a 100-mesh stainless steel press filter in the inlet water filter. The number of water filter heads to the end should be larger than 100 mesh (temporary use, after commissioning, the bypass valve is opened). If the system has a standby pump at the same time open the main backup pump, so that the maximum flow in the water pipe, open the filter after 24 hours cleaning. This will almost all of the large particles of impurities accumulated in the water filter, and then replace the 60-mesh water filter to start debugging. In addition to facilitate the user's own filter, it is recommended to install the ball valve on the filter, consider the future recoil cleaning heat exchanger outside the heat pump unit out of the water pipe to install three-way ball valve. Schematic diagram is as follows: 2 household heat pump water flow detection method 2.1 household heat pump water flow detection In the household heat pump water flow detection at present there are two simple and practical, low-cost test forms, one is the target Type flow switch, the other is the differential pressure flow switch, the following comparison of the two detection methods of installation and use characteristics. 2.2 target flow switch installation and use of the target flow switch is installed in the water pipe in the target, the water pipe hit the flow of water so that the flow of film bending deformation, which led the micro switch output control signals to the module unit controller, Inform that water flow can start the unit. Due to the relatively small pipe diameter of household heat pump units, the installation of the target flow switch brings a certain degree of difficulty. Target flow is usually installed in three situations: one is not action, the second is stuck in the upper tube can not be restored, the third is normal. The installation is very good situation and the pipe diameter and installer experience is very relevant, the larger the diameter of the target flow switch installation accuracy, the installation of household air-conditioners for household heat pump unit when the target flow switch An installation failed to rate as high as 70%. In general, the target slice does not move because the depth of the target slice is not sufficient and the target slice needs to be screwed in again or replaced. Many installers encounter this situation if they can not quickly solve the problem of often shorting the water flow switch or adjusting the action adjusting screw, thus the module unit loses water flow protection. If the card can not be recovered in the pipe is often the target is too wide, so the first action was stuck in the upper part of the pipe (in this case in the small diameter coolant pipes appear more), this is the installer can not be found At this point, the flow switch also lost its effect. If the installation gap is not enough even if you can work at that time, due to the tube rust or scaling caused by the actual use of smaller diameter, may also make the water switch stuck in the pipe can not be effective action. In addition, when the air system is mixed with air, the air in the water will impact the target flow rate and the flow rate will decrease. The instantaneous flow rate of the target flow rate will be reset to the unit (to avoid this error, the unit controller delays the flow information processing). At the same time, the target flow chip of the target flow switch will be flexed and deformed by the water flow for a long time under normal use, which is easy to be damaged by fatigue. Especially when it is installed in a vertical pipe and the flow velocity exceeds 3 m / s, its life will be greatly shortened. Generally, Type flow switch life of one year, which is large and medium-sized chillers basic annual replacement of the target flow switch causes. 2.3 Differential Pressure Flow Switch Installation and Use The differential pressure flow switch is based on the resistance and flow curve of the HVAC equipment. We know HVAC equipment, heat exchangers, water filters, pumps and valves and other devices have their resistance and flow curve, by measuring the water pressure at both ends of its access, and with the device's pre-set value for comparison, You can accurately control the traffic. Differential pressure is a precise flow control method compared to target flow switches, with accurate flow control values. It is installed directly in the unit, to prevent the user from installing the incorrect situation appears. If installed in the unit from the pressure switch to connect the two brass to the import and export of heat exchangers, measuring the pressure difference between import and export, that reflects the flow. The user site does not require installation and wiring, it also avoids the installation of the target flow switch is not accurate lead to the hidden dangers of unit failure. Pressure-flow switch with accurate flow control, no additional resistance to the system, but also on the diameter of the water pipe does not require interference and interference characteristics such as water flow can replace any form of target flow switch as HVAC water flow control system, Compared with the target flow switch, it can avoid the fake flow caused by the pump cavitation (the actual flow rate is very big, but the air is mixed with the air and the actual flow rate is not big), so it can be widely used in the brazed plate heat exchanger, Type heat exchanger and shell and tube heat exchanger modular air-cooled heat pump water flow control unit with both partial frost protection. 3 differential pressure water flow switch in household units 3.1 water flow protection For household use brazing plate heat exchanger or bushing heat exchanger pressure and flow curve may vary, but in The factory passed the test using a fixed set point differential pressure switch to ensure that the configured differential pressure switch is protected with the appropriate flow rate value
