Let’s take a step back in time and see how things have changed over the last 100 or so years. Control systems have been in use for thousands of years, but they have come a long way since their early days. In ancient times, people used various natural methods to control the temperature and air in their homes, such as using fireplaces, opening windows, and building homes in certain locations to take advantage of natural ventilation. However, the first modern HVAC system was developed in the late 1800s, when the first electric fans and central heating systems were invented. These systems were very basic by today’s standards, consisting of simple ducts that delivered heated or cooled air to different parts of a building. They were often noisy and inefficient, and they didn’t have the sophisticated controls that we have today. In the early 1900s, the first air conditioning systems were developed, but they were only used in industrial settings at first. It wasn’t until the 1920s that air conditioning began to be used in homes and businesses, but it was still very expensive and only available to the wealthy. These early air conditioning systems used large, noisy compressors and refrigeration units that took up a lot of space and required a lot of maintenance. In the 1950s and 60s, central air conditioning became more common in homes and businesses, but it was still expensive and not very efficient. It wasn’t until the 1970s that HVAC systems began to incorporate energy-saving features such as variable speed fans, programmable thermostats, and zoning controls. These features helped to make HVAC systems more efficient and affordable, and they remain an important part of modern HVAC systems today.