heating water

Figure 2-31
supply duct
blower
coil (4-tube pass)
return duct
air filter
drip pan
condensate drain
(with trap)
High wall cassettes are typically turned
on and off using a handheld remote. The
speed of the fan can be adjusted from
the remote or automatically for specific
modes of operation. For example, a low
fan speed is used when the unit is set for
dehumidification mode, allowing the coil to
extract more moisture from the air stream.
Figure 2-32
2-pipe air handler
in heating mode
2-pipe air handler
in cooling mode
Some fan-coils are available for recessed
mounting in wall cavities. Some have
air filters, while others do not. They are
available in a wide range of heating and
cooling capacities depending on size and
source water temperature.
AIR HANDLERS
The combination of a water-to-air heat
exchanger and blower is also the basis
for a category of devices known as air
handlers. Figure 2-31 shows a typical
vertically oriented hydronic air handler.
Air handlers are also available with
horizontally oriented cabinets.
Air handlers, as well as some fan-coils,
are available in either “2-pipe” or “4-pipe”
configurations. These configurations are
shown in Figure 2-32.
heated water
(supply & return)
heated water
(supply & return)
4-pipe air handler
in heating mode
OFF
zone
valves
chilled water
(supply & return)
4-pipe air handler
in cooling mode
OFF
chilled water
(supply & return)
22