There are the following items in the detection indexes of fan coil units: air volume, cooling capacity, heating capacity, cooling capacity per unit fan power, water resistance, A sound level noise, condensation, condensate treatment, temperature rise of motor windings, thermal insulation resistance, leakage current and grounding resistance. However, the standard for evaluating the quality of a fan coil in engineering mainly depends on its air volume, cooling capacity, noise and power consumption.
Usually, when choosing fan coil units, many people think that the fan coil unit technology has already passed, and the products of each manufacturer are similar, so they are often only considered from the price. From the above table, we can see that there are many differences in cooling capacity, power consumption and noise of products from different manufacturers. However, only in terms of power consumption, the difference between the maximum power consumption and the power consumption of the same product is 23W. If an office fan coil is operated for 10 hours every day and 200 days every year (the annual service factor is 0.6), 27.6 kWh can be saved every year, and the annual operating cost 30 yuan can be calculated by the 1.1 yuan of each kWh. If the price difference between the two is 100 yuan, the increased initial investment will be recovered in more than three years. This is only the economic account, which does not include the benefits brought by low noise fan coil units to improve work efficiency and the physical and mental health of staff. The following will talk about some points that should be paid attention to when selecting specific models.
1. Insufficient cooling capacity of fan coil unit: This problem is one of the most complaints from users at present. The main reasons for this problem are that many enterprises do not have their own testing methods, the parameters on the samples are copied from the samples of other manufacturers, and the thermal performance of the coils produced by themselves is poor (this is mainly caused by fin form, tube expanding quality, production process, etc.). Therefore, it is suggested that attention should be paid to the testing facilities and means of the manufacturer during the project inspection. It is hard to imagine that a manufacturer without its own testing device can produce good products.
2. Air volume: At present, in the specific engineering design, we often choose fan coil units by consulting the samples of relevant manufacturers according to the calculated cooling load. How to consider the air volume of coil is a problem. In the domestic market, most manufacturers only have one type of coil with three rows of tubes, but some manufacturers also provide coils with two rows of tubes. The author thinks that it is more advantageous to choose the coil with two rows of tubes for most civil building air conditioning systems (except for high humidity occasions). This is because the air volume of the products with two rows of tubes is larger under the same cooling capacity, which will increase the air exchange rate of the air-conditioned room, and help to improve the air-conditioning accuracy and comfort. Under the same cooling capacity, using air supply with small temperature difference and large air volume will achieve better air conditioning effect than air supply with large temperature difference and small air volume.
3. External residual pressure: According to the current national standard of fan coil units in China, the air volume, cooling capacity, noise and other parameters of fan coil units are tested under the condition that the external static pressure is 0. However, in actual use, a short section of air duct and outlet louver are often connected before the outlet of fan coil, and some projects are also equipped with return bellows. Therefore, in actual use, it will be found that the actual air volume of the coil is less than its nominal air volume, which results in the decrease of room air volume, the increase of air supply temperature difference and the decline of air conditioning comfort. In order to avoid this situation, some designers choose the mid-range air volume of fan coil units to avoid insufficient air volume, but increase the initial investment of the project.
4. Noise problem: This is a place where there is a big product gap at present, and it is also a key point that fan coil units are complained about due to quality problems at present. The reason for this problem lies in the unreasonable configuration and matching of motor and fan in fan coil unit. Another reason is that the manufacturer's quality management is lax, and the assembler's sense of responsibility is not strong, resulting in unstable product quality. Therefore, when examining a manufacturer's products, we should refer to the noise detection report issued by the national authoritative quality inspection department (pay attention to the products we are going to order). For the selected projects with large quantities, they should be sampled on site and sent to relevant quality inspection departments for inspection.
In addition to the above mentioned items, attention should also be paid to whether there is a qualified report of condensation test issued by the quality inspection department when selecting coils. Overall insulation shall be adopted for the condensate tray, and long tray shall be preferred for the water tray. In addition, products with small appearance and light weight should be given priority under the same conditions. At present, the products of most domestic manufacturers can reach the standard, so it is not the focus of investigation.
In a word, in the actual operation of central air-conditioning system, specific analysis should be made according to specific conditions, which I think all suppliers and engineers of central air-conditioning terminal products should understand.