Introduction

Introduction

The purpose of Heating, Ventilating and Air Conditioning (HVAC) control systems is to keep people comfortable within an enclosed space. Although comfort control is thought of as achieving a desired temperature in a building, it is also achieved by maintaining a desired level of humidity, pressure, radiant energy, air motion and air quality.

One of the most popular HVAC applications, the Variable Air Volume (VAV) application, is designed to deliver low energy cost, low maintenance and good comfort performance. The VAV application controls the temperature inside a space by modulating the amount of air supplied to it. VAV systems, which are studied in this chapter, are easy to install, commission and service. They are also simple to understand and represent a good introduction to HVAC controls.

In this tutorial, the VAV system is analyzed, modeled and simulated. The air handling system, which provides air to the VAV system, is also studied and analyzed. When modeling the different components of the VAV system, practical models are used to capture the different characteristics of the system. The VAV system components used in this tutorial are fairly simplified using first order system modeling and piece-wise linear modeling techniques. The different models used to simulate the VAV system response are easy to develop and are great for engineers who are interested in observing the general behavior of the system rather than the minute details.