A fan coil unit is one of the simplest methods to heat and cool. The basic fan coil system consists of an air coil and a motor-blower assembly. 

Whether the unit operates with a free-return, plenum return, or an exposed cabinet, the basic operation of the unit is the same. By passing air from the occupied space across the air coil, heat is added to, or removed from, the air stream as it is supplied back to the occupied space.

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