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Heating and cooling are two of the most important concepts of home ownership. They are also major factors for those looking to purchase homes since they are a critical part of living comfortably.

There are a lot of pieces and parts that go into each home’s unique HVAC system. That’s why we broke down everything you need to know about heating and cooling — like how HVAC systems work, what products go into each type of system and how thermostats control them. Knowing this information will ensure that you’re an informed homeowner, as well as an informed home buyer.

What is HVAC?

You may frequently hear the term ‘HVAC,’ which is used to describe home heating and cooling systems. The acronym stands for Heating, Ventilation and Air Conditioning, which are the three primary functions of a home system.

HVAC systems control air temperature and humidity and maintain the quality of the air in the home. Each of the systems have individual jobs, but also work together to create balance and comfort within your home.

Central Systems

You can classify heating and cooling systems as central or local. Central heating and cooling is the most standard method, and is defined as a system that produces warmth or cool in one central area and then distributes it throughout the home. There are many types of systems that work as central systems, from traditional split systems to packaged product systems.

Products typically used in central heating and cooling systems include:

  • Heat pumps. While other heating units generate temperatures, a heat pump is a mechanical-compression cycle refrigeration system that moves hot or cold air (depending on the season) from the outdoors to inside your house. Quite often, heat pumps work in collaboration with supplemental heating and cooling methods.  
  • Air conditioners. A central air conditioner pumps chilled air throughout your house through a system of air ducts. A home’s thermostat tells the system when to turn on or off depending on when the temperature rises or falls. 
  • Gas and oil furnaces. Most central heating systems will have a gas or oil furnace located in the basement or garage. The furnace’s purpose is to create combustion gases that warm the air and distribute it through ducts. 
  • Fan coils. A fan coil (also known as a condenser coil) works with a heat pump to house electric resistance heat that provides warm air during winter months.  
  • Evaporator coils. Evaporator coils are like fan coils, but they work with an air conditioner to remove heat from a building.
  • Controls and thermostats. A thermostat works by sensing air temperature and switching on or off to meet the desired thermostat setting. Modern digital thermostats use a thermistor to measure temperature.

Local heating and cooling, on the other hand, produces heat at the location where it is needed and serves small spaces. Room air conditioners and Packaged Terminal Air Conditioners (PTAC) are examples of local heating and cooling.


Heating systems keep your home warm and comfortable. If you live in a particularly cold climate, the function of your heating system is a high priority. Most central heating and cooling systems are classified as forced air systems, because they send air through ductwork for distribution. The ductwork can contain products that filter or clean the air as it moves through. Radiant systems create heat and deliver to its components such as radiators that radiate the heat into the home. Boilers are another common radiant heat source.

Typical heating products include:

  • Heat pumps. While most homes tend to use heat pumps in conjunction with other supplemental heating sources, some homeowners will use them alone. In general, heat pumps work best in moderate climates. 
  • Gas and oil furnaces. Most American households depend on a central furnace to provide heat. They can be powered by electricity, natural gas or fuel oil. 
  • Fan coils. A fan coil unit is a device that includes a heating exchanger (or a coil) and a fan. It sometimes uses ductwork and controls the temperature in the space you install it. 
  • Boilers. A boiler is a pressure vessel that provides a heat transfer between combustion products and water. It’s often integrated into a complete heating system.  


Whole-home air conditioning systems are central systems that rely on ducts to deliver cooled air throughout the home. An air-conditioning system provides cooling, ventilation, humidity control and can even provide heating (if using a heat pump) for a home. Air conditioning units cool refrigerants like Puron® Refrigerant and Freon and deliver them to evaporator coils, which dissipate the refrigerant and blow it into ducts for delivery throughout the home.

Products such as room air conditioners are local cooling options for smaller areas within homes. Instead of delivering cooled refrigerant to a coil and then to ductwork, a room air conditioner contains all the components in a single unit and blows air directly into a room.

Air-conditioned homes often have sealed windows, because open windows would disrupt the attempts of the control system to a maintain constant temperature.

Typical air conditioning products include:

  • Heat pumps. While heat pumps are often used to generate warmer temperatures, they can also cool a climate. Instead of moving heat from a warm space to a cool space, it does the opposite and moves the warm air out of your home. 
  • Central air conditioners. A central air conditioner pump chills air throughout the house through air ducts. They often use the same system utilized by a forced-air furnace during the heating season.
  • Room air conditioners. If your home doesn’t have a central air conditioner, you can use a room air conditioner. These units use refrigeration principles to extract heat and moisture from room air, cooling and dehumidifying the air.


The term thermostat commonly refers to any unit that controls the operation of a heating and cooling system. Thermostats are used to turn on heating or cooling systems to bring the home to a desired temperature. In addition to basic temperature control, programmable thermostats can be used to manage the timing of the system’s functions, which can control overall energy use and costs.

What are common HVAC issues?

As the seasons change, different problems may arise in your heating and cooling system. That’s why it’s important to schedule routine maintenance visits before you risk your family’s comfort. There’s not a worse time for your heater to malfunction than the first cold day of the season. Here are the types of issues that leave homeowners seeking Alexandria HVAC service each year:


  • Uneven heating. If some of your rooms are staying warm, but others are falling short, it may be one of two things. For one, it could be a draft issue. If this is the case, you may want to get an energy audit to see where air is leaving your home. If it’s not insulation, it may be an HVAC issue. Check your vents to make sure they’ve adjusted appropriately and check that the air filter isn’t dirty. You may also want to call in an HVAC pro to replace dirty coils or check your ductwork
  • Carbon monoxide leak. Since it’s hard to detect, carbon monoxide is known as the silent killer. If your gas furnace is more than 10 years old, it’s important to scheduled annual inspections to ensure there isn’t a carbon monoxide leak that is emitting through the cracks in a rusted heat exchanger. 
  • Sudden heat loss. If your heat stops out of nowhere, first check if a breaker has tripped. If not, you may have an electrical problem or a pilot light that went out. Since both of these repairs can be quite dangerous to perform, it’s best to leave them to a professional.


  • AC isn’t cooling. If your AC isn’t cooling your home, it may be something as simple as a closed vent. If your vent is open and your unit still isn’t working, there may be a leak in the refrigerant line. Never handle refrigerant on your own — this is best left to those that are professionally trained. 
  • Spiking energy bills. It’s normal to see fluctuations in your energy bills during the high heat of summer. What isn’t normal, however, are numbers that aren’t consistent with your annual payments. If your bill is sky high, you may have dirt and dust built up that’s stopping it from working as expected. That’s why it’s important to have your unit cleaned at least twice a year. 
  • Strange noises. A little humming is nothing to be concerned about. If your HVAC unit is making strange noises (like rattling, screeching or thumping), then it may be working too hard. You may also have loose hardware, a failing motor or a need for oil.


  • Clogged systems. As leaves fall to the ground, they can get sucked into vents and stuck in your HVAC system. If your system is running poorly, schedule a maintenance visit to regularly clean out the leaves. 
  • Sensor failure. Fall is one of the most unpredictable seasons — and those temperature changes can put a strain on your system, causing your sensors to fail. If you notice your system is struggling to fluctuate temperatures, it’s time to talk to a maintenance specialist.  
  • Refrigerant leaks. As the weather cools down from a hot summer into the fall, your system will be under a lot of pressure. As a result, your refrigerant pipes may leak — which is a  very dangerous side effect of being overworked. To avoid this issue, select a regular maintenance agreement that includes a refrigerant check.  


  • Overheated unit. If your HVAC unit overheats, it may be because of something as simple as an overdue filter change. It’s not uncommon to need a new filter after the heavy demands of the summer. If your filter gets clogged with dirt, your unit can overheat and shut off.  
  • Dirty coil. Over time, both the evaporator coil (located inside your home) and condenser coil (located outside your home) can become filled with dust, dirt and other debris. The springtime is generally an appropriate season to thoroughly clean these parts. 
  • Contractor switch. One of the most common spring HVAC issues is a bad contractor switch. If your thermostat is on but neither the condenser nor the air handler start, it’s time to call an HVAC contractor to replace your contractor switch.

Let’s chat HVAC

Have questions about your HVAC system? This Alexandria home service company is here to help homeowners and businesses in Washington, D.C., Northern Virginia and Maryland. Just call 703-214-5611!

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