Introduction
In the previous chapters we have discussed ventilation for maintaining indoor air quality, the thermal requirements for comfort, and reasons for zoning a building. In this chapter we are going to consider packaged single-zone air-conditioning equipment, examine issues of system choice and provide a general description of system control issues. We will return to controls in more depth in Chapter 11.
The single-zone air-conditioning equipment we will be discussing is the piece of equipment that was introduced in Chapter 2, Figure 2.12. This unit is typically referred to as the single zone air handler, or air-handling unit, often abbreviated to AHU. In this chapter, we will refer to it as the air handler or the unit. The air handler draws in and mixes outside air with air that is being recirculated, or returned from the building, called return air. Once the outside air and the return air are mixed, the unit conditions the mixed air, blows the conditioned air into the space and exhausts any excess air to outside, using the return-air fan.
Before getting into a discussion of the components of a single-zone package air-conditioning unit, we need some context as to where it fits into the whole building or site systems.