What are HVAC Systems?

Ken Black

HVAC systems are any systems that deal with heating ventilation and air conditioning. These systems are sometimes called central heat or central air conditioning systems and use air ducts by which to move the air throughout the building. At one time considered a luxury, HVAC systems are now commonplace in new buildings, especially in industrialized nations.

A residential thermostat for an HVAC system.
A residential thermostat for an HVAC system.

Parts of an HVAC system include the heating or air conditioning unit, the ductwork, and vents, both intake and outtake. The intake vents return air to the the heating and cooling units through the ducts. The outtake vents distribute heated or cooled air throughout the rest of the home. A thermostat is also considered part of the system.

An air conditioning unit.
An air conditioning unit.

Most HVAC systems are powered by air conditioning units and furnace units. In some cases, one or the other may be the only one present. For example, at higher latitudes, it is common for older homes to have only a furnace. Air conditioning is not needed during many times of the year and was considered a needless luxury. While most homes now have complete HVAC systems, there still may be a few that don't.

An air return duct is an important part of most air conditioning HVAC systems.
An air return duct is an important part of most air conditioning HVAC systems.

HVAC systems may be powered a number of different ways. For the furnace, natural gas is, by far, the most popular option, followed by some type of heating oil and finally electricity. Often, the economics dictate what type of fuel will be used in a certain area. Most homeowners will obviously choose the cheapest, but most effective, option possible. Most furnaces are rated for their efficiency on a standard scale which can be compared to other models.

For the air conditioning part of HVAC systems, the most common power source is electricity. The cost of electricity can make cooling a home a very expensive proposition. Often, people may make a trade off, accepting a less efficient unit for heating or cooling depending on the part of the system that will be idle throughout a greater part of the year.

HVAC units are often rated by looking at a specific measurement. There are different measurements for different units. For example, the annual fuel utilization efficiency (AFUE) rating is used for furnaces. Anything below an 80 is considered a fairly inefficient unit. Anything rated 90 or higher is considered a super efficient unit. The seasonal energy efficient rating (SEER) is often used for air conditioners. The scale for a SEER is slightly different, but a higher rating is good. All new air conditioners in the United States must meet a standard rating of at least SEER 13.

HVAC systems provide necessary heating, cooling and ventilation to a building, in a way that provides maximum comfort to occupants.
HVAC systems provide necessary heating, cooling and ventilation to a building, in a way that provides maximum comfort to occupants.

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Discussion Comments


I agree with the article above, It has clearly stated, all the important points given for the HVAC systems, about the maintenance, repair, and replacement.


@fiorite- When considering HVAC repair, remember it is not only about how efficient your system is. HVAC systems play an integral role in indoor air quality. You may have code violations for indoor air quality because of your HVAC unit. If you really think that the unit is defective, and it is causing other problems like mold growth (excessive humidity) you may want to have someone come inspect your home.

An Environmental inspector can do a complete air quality assessment and identify the source of your problem. Worst-case scenario, this may be necessary for you to persuade your property manager to fix the problem. Good luck!


@fiorite- When to replace an HVAC system really depends on the system and how well it was maintained throughout its life cycle. An HVAC system by design can be repaired for at least 20+ years. The decision to replace depends on the costs and benefits of doing so. After about 15 years, the cost of overhauling an HVAC system can is more than replacing it all together. This is especially true if you consider the increased efficiency of new systems and the rebates for installing efficient equipment.

Since your property manager is responsible for replacing the unit, it will ultimately be up to him or her to replace the unit. As long as the unit’s condition is not affecting your lease agreement, causing undue costs to you, or posing an immediate danger to the occupants, the property manager does not have to replace it. I would propose the idea to the property manager in the terms of costs and benefits. In my opinion, this will be the easiest way to get your unit replaced.


How do I know if a residential HVAC system needs to be replaced? I have a furnace/air conditioning unit that is about 20 years old and is not very efficient. I want to get my property manager to replace the unit, but I do not know what would make a unit go bad. The unit has humidity control problems, the fan never turns off unless I shut the unit off completely, and it has trouble cooling when I use high quality filters. It is also in need of repair every three months (I live in the desert). How can I justify its replacement?

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