Maintenance and maintenance of commercial central air conditioning
At present, with the intensification of competition among commercial enterprises, the shopping environment is closely related to the benefits of enterprises. Central air conditioning systems are designed and installed in large and medium-sized shopping malls. The investment cost of central air conditioning system accounts for about 10% of the total investment, while the usual operating cost accounts for 40%~60% of the total energy cost. For example, in a shopping mall in Nanjing, the cost of air conditioning in summer (only calculating the electricity bill) spent about 80% of the total profit in the whole summer. Without the maintenance of central air conditioning system, the refrigeration effect of air conditioning is getting worse and worse, the power consumption is getting worse year by year, the cost is getting higher and higher, and the equipment is seriously damaged. Some users' air conditioning systems have been basically paralyzed for more than a year. For example, according to the characteristics of the central air-conditioning system of the unit, the management operator carefully studies and formulates the maintenance plan, so that the central air-conditioning system always runs in an efficient and energy-saving state.
The central air conditioner in shopping malls is used to adjust the temperature and humidity of shopping malls and replenish fresh air all the year round to improve the comfort of shopping environment. Its characteristics are as follows: 1, and the shopping mall has a high pedestrian density (generally, the daily peak of passenger flow often appears in the morning 10 ~ 16 and in the afternoon 13~ 16). 2. The instability and randomness of shopping mall passenger flow make the air conditioning load unstable, which requires the air conditioning system to have good off-design performance and sensitive adjustment ability. Shopping malls are open every day, and the climate changes greatly in the four seasons. It is required that the operating conditions of air conditioning in shopping malls should be adapted to it, not only to meet the peak load of individual bad weather, but also to have good economic performance under low load conditions most of the time.
2. Maintenance and maintenance
2. 1 freezer
The choice of cold source equipment for central air conditioning system in shopping malls will be comprehensively considered according to power supply, investment, building scale and other factors. According to the investigation of the types of units used in the central air-conditioning system in shopping malls, if users pay attention to maintenance from these aspects, the service life of air-conditioning equipment will be prolonged and the rate of cooling efficiency decline will be slowed down.
2.2 Water system
2.2. 1 cooling water system
The cooling water system consists of condenser, cooling tower, water pump, pipeline, valve and filter, and its function is to discharge the heat in the refrigeration system to the atmosphere. The condenser in the central air conditioning system will gradually form a layer of scale on the water side. The longer the condenser is used, the harder the water is and the thicker the scale is. Due to the small thermal conductivity of scale, the heat transfer effect of condenser is affected, resulting in poor refrigeration effect of refrigerator. Therefore, corresponding measures must be taken to remove the scale on the water side of the condenser. Traditional descaling methods for condenser water side include manual cleaning, mechanical cleaning and chemical cleaning. In recent years, some shopping malls have installed electronic water treatment instruments in the cooling water system of central air conditioning, and it is considered that impurities in water cannot be removed by discharging pollutants alone, which is often ignored by air conditioning operators. It is wrong to understand that there is no need to discharge sewage when an electronic water treatment instrument is installed. Each method has its disadvantages. In this way, only when the scale on the water side of the condenser affects the normal operation of the whole refrigeration system will the scale on the condenser be cleaned. The new generation water treatment instrument can measure the water temperature and the solubility of total solids in water, and then automatically adjust the operating parameters of the instrument. However, the pollution discharge work can not be ignored.
Legionella infection and its countermeasures: 1976 Legionella was found in Philadelphia, USA. 198 1 year, the first case of Legionella was found in Nanjing. The survival conditions of Legionella are: when the water temperature is 25℃-42℃ (in which the water temperature is 37℃), the reproduction is the fastest, the water body is stagnant, and the water contains a large number of scales, sediments, microbial membranes and amoeba, which will reproduce rapidly and may threaten human health.
The cooling water system in central air conditioning equipment provides favorable conditions for the survival and reproduction of Legionella: First, the cooling water temperature is 31℃-35℃; Secondly, a lot of air is washed away by cooling water, and dust, organic matter, microorganisms and their debris are accumulated in the cooling water system, which provides a source of nutrition for the reproduction of Legionella. In this way, the cleaning of cooling towers and pipelines can reduce the nutrients needed for the growth of Legionella.
Effective measures to prevent legionnaires' disease: A. Add disinfectant and algaecide into circulating water of cooling tower regularly. ARKO—400 germicide and algaecide produced by a company in Taiwan Province has a good inhibitory and killing effect on Legionella, which solves the problem that the cooling tower is covered with moss due to sun exposure. Add it once a week B regularly clean the cooling basin and reservoir to remove the spoilage and sundries of microorganisms in the water as nutrient sources, thus reducing the reproduction of microorganisms. It is suggested that high-grade air conditioner scale remover produced by a factory in Guangdong can be used for cleaning 1-2 times a year, which is fast and convenient. C regularly check the water quality, and decide the water change time according to the water quality. D ensure a certain amount of make-up water to reduce the evaporation and concentration of cooling water.
2.2.2 cooling water system
Generally, tap water is used as water in a chilled water system. The water in the system is not in contact with air and exposed to sunlight, so the water quality is not easy to deteriorate. When the water quality deteriorates, the main reason is not scaling, but corrosion. These corrosion are caused by oxygen brought by supplementary water, galvanic corrosion caused by various metal materials and the growth of anaerobic microorganisms. The sludge formed by corrosion will also cause water quality deterioration and pipeline blockage, especially the fan coil water filter is easy to block, which will affect the refrigeration effect and leakage over time. ARKO-50 1, a closed system corrosion inhibitor produced by a company in Taiwan Province, can effectively prevent the corrosion of all metals in the pipeline system and prevent the formation of precipitates after being added to the chilled water system. Users only need to add it once a week.
2.3 Terminal Equipment Maintenance and Indoor Air Quality
2.3. 1 Maintenance of fan coil unit, fresh air unit, surface cooler and combined air conditioning box.
The terminal equipment of the central air-conditioning system carries out heat and humidity treatment on the air, and sends it into the air-conditioned room after reaching the set value. Some common faults will occur after these devices are used, and the countermeasures to solve these problems are put forward.
2.3.2 Indoor air quality and air purification equipment
The reasons for the poor air quality in shopping malls are as follows: a. Poor ventilation in shopping malls and poor air filtration in air conditioning systems have formed a closed circulation system among people, shopping malls and air conditioners. In this system, the human body can't get enough fresh air, which causes some weak customers or salespeople to faint in the shopping mall. It is understood that the standard of adequate oxygen concentration required by human body should be 2 1%. Medical monitoring data show that if the living space is not ventilated for several hours, the oxygen concentration will drop to 17~ 19%, which will affect the normal demand for oxygen and lead to dizziness and fatigue. B, building decoration materials and all kinds of furniture in shopping malls constantly emit high concentrations of toxic and harmful substances such as formaldehyde, chloride and benzene. C, customers, shop assistants in the mall activities, through the respiratory tract, sweat glands discharge a lot of pollutants. D. Shopping malls are generally located in areas with convenient transportation, and there are many vehicles, so the tail gas emitted by vehicles inevitably rushes into the shopping malls. In order to create a good shopping environment, it is necessary to treat indoor air technically. Table 3 gives the ultraviolet sterilization technology, installation location, effect, function and application occasions. Cleaning the filter screen regularly or irregularly and choosing qualified filter screen can avoid black stains at the tuyere and affect customers' shopping desire in the mall.
3. Conclusions and recommendations
Refrigerators and systems should be overhauled once a year according to operation and maintenance procedures; Pay attention to water quality treatment; Regularly clean the filter of terminal equipment; Conduct targeted training for the person in charge and staff of the maintenance management operation department, so that they can fully understand and be familiar with the management control and maintenance technology of HVAC system; Study the environmental requirements of customers when shopping in shopping malls, and provide the monthly energy consumption and expenses to operation management technicians, so that managers can pay attention to energy consumption, formulate energy-saving operation indicators for the next month, and make tables of outdoor temperature and energy consumption for each month for reference by operation management technicians.