Fan Coil System advantages
A major advantage of the fan-coil unit system is that the delivery
system (piping versus duct systems) requires less building space—
it requires a smaller or no central fan room and little duct space.
The system has all the benefits of a central water chilling and
heating plant, while retaining the ability to shut off local terminals
in unused areas. It gives individual room control with little
cross-contamination of recirculated air from one space to another.
Extra capacity for quick pull down response may be provided. Because
this system can heat with low-temperature water, it is particularly
suitable for solar or heat recovery refrigeration equipment. For
existing building retrofit, it is often easier to install the
piping and wiring for a fan-coil unit system than the large ductwork
required for an all-air system.
Fan Coil System disadvantages
Fan-coil unit systems require much more maintenance than central
all-air systems, and this work must be done in occupied areas.
Units that operate at low dew points require condensate pans and
a drain system that must be cleaned and flushed periodically.
Condensate disposal can be difficult and costly. It is also difficult
to clean the coil. Filters are small, low in efficiency, and require
frequent changing to maintain air volume. In some instances, drain
systems can be eliminated if dehumidification is positively controlled
by a central ventilation air system.
Rooms are often ventilated by opening windows or by outside wall
apertures, if not handled by a central system. Ventilation rates
are affected by stack effect and wind direction and speed.
Summer room humidity levels tend to be relatively high, particularly
if modulating chilled water control valves are used for room temperature
control. Alternatives are two-position control with variable-speed
fans and the bypass unit variable chilled water temperature control.