The choice of fan coil unit is a key issue. It is a common practice in air-conditioning system design to select coil units based on the cooling load of the air-conditioned room to ensure room temperature during peak loads. In fact, the air-conditioned room will not be at peak load most of the time, which will lead to excess cooling capacity. Instead, it switches to low-to-mid-range operation, reducing the output of cooling capacity, thereby maintaining the thermal balance of the room. When selecting a fan coil unit, in addition to the cooling capacity to meet the requirements of calculating the cooling load, it is also required to meet the matching of sensible heat and latent heat to meet the requirements of room heat-humidity ratio; the air volume meets the requirements of supply air temperature difference, ventilation times and airflow organization. As the terminal equipment of the central air conditioner, the quality of the coil determines the effect of the indoor air conditioner. At the same time, its cleaning problem also directly affects the use effect of central air conditioning. There are many dust particles in the atmosphere. Under the action of suction and return air for a long time, the aluminum fins of the fan are covered with dust and dirt. At this time, on the one hand, the heat exchange between the cold water and the hot air is affected, and the air temperature drops. On the other hand, it also affects the delivery of cold air that has been cooled after heat exchange, resulting in the phenomenon that the room is still not cold when the air conditioner is turned on.