Although most fan-coil units are located beneath
windows on exterior walls, they may also be mounted
horizontally at the ceiling, particularly for installations
where cooling is the primary concern.
Technically, a fan-coil unit with an outside air inlet
is called a unit ventilator. Unit ventilators provide the
capability of using cool outside air during cold weather
to provide free cooling when internal loads exceed the
heat lost through the building envelope. See the discussion
of economizers, §10.5.5.