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, feedback noise is not uncommon.
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 even being designed by formal design units. The noise of fan coil units in use is directly affected by unit selection, installation methods and duct materials. The irregularities in air conditioning system design, air conditioning installation and duct material selection have resulted in various installation forms of fan coil units in the market, which is accompanied by loud noise, which affects the comfort of use.
The following is a summary and analysis of fan coil design, installation and duct material selection.
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 select the large No.1 unit, ignoring the noise value requirement of the unit itself, and only when it is used will it be found that the noise of the unit is too large, resulting in a decrease in the use comfort.
On the other hand, in the selection of static pressure for air supply of units, certain air 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 static pressure of 30Pa or even 50Pa 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 will directly lead to excessive air volume during use, which will lead to increased noise.
2. Analysis of the influence of installation mode on noise.
Because there is no perfect guidance document in the installation of fan coil units, and the experience and strength of engineering units are uneven, the installation forms of fan coil units are diverse, and many unreasonable installation methods lead to loud feedback noise from users.
In places with high noise requirements, it is suggested that air ducts should be added before and after the unit, and noise reduction measures should be added 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 low and the air duct is short, improper selection will directly affect the noise of the units.
In the selection of duct materials, in places where noise is required, it is necessary to pay attention not to choose smooth 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 a lot of 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 have been counted and analyzed, and it is suggested to choose duct materials with sound attenuation function on the inner wall for places with high noise requirements, which can greatly improve the comfort of use.