An air-handling unit consists of a fan, heat
transfer surface, and casing.
A remote air-handling unit or a remote
air-conditioning unit is a unit located outside of
the conditioned space that it serves.
Self-contained air-conditioning units may be
divided into two types: window-mounted and
f l o o r - m o u n t e d u n i t s . W i n d o w - m o u n t e d
air-conditioning units usually range from 4,000 to
36,000 Btu per hour in capacity (fig. 7-5). The use of
windows to install these units is not a necessity. They
may be installed in transoms or directly in the outside
walls (commonly called a "through-the-wall"
installation). A package type of room air conditioner,
showing airflow patterns for cooling, ventilating, and
exhausting services, is shown in figure 7-6.
In construction and operating principles, the
window unit is a small and simplified version of much
larger systems. As shown in figures 7-7 and 7-8, the
basic refrigeration components are present in the
window unit. The outside air cools the condenser coils.
The room air is circulated by a fan that blows across the
evaporator coils. Moisture, condensed from the humid
air by these coils, is collected in a pan at the bottom of
the unit; it is usually drained to the back of the unit and
discharged. Most window units are equipped with
thermostats that maintain a fixed dry-bulb temperature
and moisture content in an area within reasonable
limits. These units are installed so there is a slight tilt of
the unit towards the outside, toward the condenser, to
assist in drainage of the condensate. It is a good idea to
mount the unit on the eastside of the building to take
advantage of the afternoon shade. These units require
very little mechanical attention before they are put into
operation. Window units are normally operated by the
user who should be properly instructed on their use.
Floor-mounted air-conditioning units range in size
from 24,000 to 360,000 Btu per hour and are also
Figure 7-5.Window air conditioner.