Evolution of the central heat and air unit


The evolution of the central heat and air unit extends back at least a few thousand years. The advances were more in the approach than basic concept.

The First Central Heating and Air Conditioning

Most likely systems were experimented with even earlier, but widespread use was known in ancient Roman times. External fire chambers collected wood heat and routed it through floors and rectangular tile ducting in walls to centrally heat buildings. Though not a combined system, central cooling was available as well, albeit only for the very wealthy. Part of the famous aqueduct system routed water to the more elite homes, where it was circulated through the walls to provide cooling. Leaping ahead some centuries, hot water and steam heating were developed in the 1700s and 1800s respectively.

What about Other Methods?

In some cultures and even more recent times, buildings have been designed to circulate naturally heated and cooled air from basements. Since the earth maintains a relatively constant temperature, basement air will normally be cooler in summer than ambient air on the surface and in winter will be warmer.

In extreme desert areas, such as central Australia and parts of Africa and Asia, many structures, some quite famous, were built underground or in narrow chasms to take advantage of this. In India, ancient passive technology used caverns or chambers under buildings to hold large pools of water to regulate temperatures by evaporation and also act as a heat sink.

A Move Forward with Refrigeration


Experiments in evaporative cooling techniques as early as the late 1700s progressed to further work in the 1800s in which ice making was perfected. By the early 1900s, air conditioning was on its way, and by the late 1920s, true refrigeration as we now know it was commercially available, though AC for the common man was not popularized until after WWII when the economy and attention of the public was released from wartime concerns. Modern refrigeration made possible the AC/furnace combination.


The combined heat and air unit goes back 100 years, when it was used in large commercial applications, though popularization of it for homes is still in progress to this day with the largest number of central heating and air units being installed in new homes.

The heat pump, a true central heat and air unit using all the same elements to produce both heat and cooling, was developed by 1977 and is evolving, improving and gaining popularity. The newest innovation in this technology is the split system concept that allows doing away with ducting from room to room and instead provides a base unit outside for heat exchange and individual room units throughout the house for individually wireless-controlled heating and cooling.

The Challenge for the HVAC Professional


What makes the profession of the HVAC technician interesting and demanding is the fact that the technologies still in use today include overlapping variations going back well over a century, as well as those using differing fuel sources. Experts in central and air must be capable of dealing with all technologies on a competent and viable basis while still keeping up with the newest advances.

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