As one of the main supporting forms of central air-conditioning host products, fan coil unit is still widely used as a classic mode of combining with fresh air system. Fan coil units are widely used in hotels, office buildings, hospitals, scientific research institutions and other places because of their convenient installation, small size and low cost. However, there are not a few feedback noise problems during use.

At present, there are many engineering units in China, and the strength of design units is different. Some central air-conditioning systems of smaller projects are directly installed and put into use without the design of formal design units, while the noise of fan coil units in use is directly affected by unit selection, installation methods and duct materials. The nonstandard air conditioning system design, air conditioning installation and duct material selection result in various installation forms of fan coil units in the market, which is accompanied by loud noise and affects the comfort of use.

The following summarizes and analyzes the fan coil design and selection, installation mode, duct material selection and other aspects.

1. Noise problem caused by fan coil unit selection

On the one hand, in order to ensure sufficient air supply and cooling capacity when designing and selecting fan coil units, many designers will give a certain amount of air supply allowance in design, and even directly choose the large No.1 unit, ignoring the noise value requirement of the unit itself, and only when using it will it be found that the noise of the unit is too large, which leads to the reduction of the use comfort.

On the other hand, in the selection of static pressure for air supply of units, certain duct resistance allowance will be given according to design specifications, and some nonstandard designs give excessive static pressure allowance. For example, some rooms only need 12Pa because of small space, but units with 30Pa or even 50Pa static pressure have been selected. According to the characteristics of centrifugal fans, there is a certain conversion relationship between static pressure and air volume, and excessive static pressure directly leads to excessive air volume during use, which will lead to increased noise. 　　 2. Analysis of the influence of installation mode on the use noise

There is no perfect guidance document in the installation of fan coil units, and the experience and strength of engineering units are uneven, which leads to various installation forms of fan coil units, and many unreasonable installation methods lead to loud feedback noise from users.

In places with high requirements for noise, it is recommended to add air ducts before and after the unit, and to increase noise reduction measures to achieve better comfort. 3. Analysis of the influence of duct materials on the noise of fan coil units

During the use of fan coil units, although the static pressure of the units is not large and the air duct is short, improper selection will directly affect the noise of the units.

In the selection of duct materials, where there is noise requirement, it is necessary to pay attention not to choose smooth duct materials such as ordinary steel plate and aluminum foil inner wall duct, which not only has no sound absorption function, but also reflects noise to a certain extent, resulting in greater noise at the air supply outlet.

There are many air duct materials with silencing function in the market, and suitable materials can be selected according to the use places to meet the use requirements. At present, the existing common duct materials in the market are counted and analyzed, and it is suggested to choose duct materials with silencing function on the inner wall for places with high noise requirements, which can greatly improve the comfort of use.

4. Summary

To sum up, in order to improve comfort and avoid unnecessary noise, several aspects should be considered at the same time. For designers, it is required to go deep into the site as much as possible, and select the most suitable fan coil units through actual requirements, including accurate calculation of the required static pressure. In addition, it is necessary to design a reasonable installation method according to the noise requirements of the use place.

For the construction party, it is necessary to strictly abide by the construction specifications and select suitable air duct materials.