Horizontal concealed ceiling fan coil units are selected based on key control parameters such as rated airflow, outlet static pressure, input power, rated cooling capacity, rated heating capacity, noise, and water resistance. For fan coil units in a two-pipe water system (suitable for systems that only switch between heating and cooling based on the season or cooling area), a single coil set is configured, with a dual-purpose heating/cooling model for winter and summer use. For fan coil units in a four-pipe water system (suitable for systems with frequent heating/cooling switches), a combination model with both heating and cooling coil sets should be configured.