Heating and cooling systems are more complicated than we sometimes give them credit for. There’s volatile materials, electrical work, sheet metal work, often carpentry, air pressure and thermodynamic calculations, and several delicate or complicated pieces of equipment working together to provide your home with cool air.
If you don’t understand all of it, that’s ok. That’s what we’re here for.
This article explains the basics of air conditioners, but then also digs one level deeper to give you information about types of air conditioners, the technology that powers them, and what this could mean for your home HVAC (heating, ventilation and air conditioning) system.
Why is this important? Because knowing more than just the basics can lead to better decisions for your home, and a decreased chance that a contractor will take advantage of you.
Save thousands. Be more comfortable. That’s the goal. Ready to get started? Keep reading.
What is an Air Conditioner?
An air conditioner is a piece of equipment that cools a space, usually a home, apartment or commercial building. Air conditioners can be designed to cool small rooms or spaces all the way up to large buildings, which necessitate multiple air conditioning units.
Calling many air conditioners a single unit can also be misleading, particularly in the case of central air conditioners that cool most homes and businesses. These will be the primary focus of this article. Homes, for instance, will have an indoor and outdoor unit that are both part of the air conditioning system.
Even outside these indoor/outdoor units, other parts of an air conditioning system are necessary for cooling to happen, but are located in different areas of the home. We’ll discuss each in this article.
Air Conditioning Process
There are a few keys to understanding how home cooling happens. The first is the refrigerant in your system (sometimes called Freon).
Refrigerant can change states from liquid to gas, and when it’s in its gas form, it absorbs heat from the surrounding air. This is the key to understanding home cooling.
Rather than add cool air, what air conditioning actually does is remove heat from your air. The refrigerant absorbs heat in its gaseous form. It then travels to the outdoor unit, where a compressor forces it into its liquid state.
At this point, it ejects the heat it absorbed, and this heat is vented outside your home. This is why the outdoor unit and its large ventilation fan is necessary.
This is why ductwork and proper airflow is so important in a home. It’s collecting air from throughout the home for the heat to be absorbed. It’s then recirculating the cooler air once that heat has been removed.
This cycle repeats over and over until your indoor air matches the temperature set by the thermostat.
This is an extremely basic walkthrough of the cooling process. The mechanical interactions required to get everything to work in harmony to cool your home are quite complex and involve subsystems to each of the processes mentioned. However, this should give you a good overview of how the cooling process works.
Types of Air Conditioners
There isn’t a single air conditioner type, but many.
Most of the types mentioned below operate on the same mechanical principles mentioned above. However, many operate without the aid of ductwork, meaning that they aren’t suitable for whole-home cooling.
Central Air Conditioner
This is the type of air conditioning most people think of when it comes to home air conditioning. Central air units have an indoor and outdoor unit, and are connected to ductwork in a home or building.
For homeowners with existing ductwork in their home, this is the most cost-effective solution available for consistently cooling your home.
Window Air Conditioner
Window air conditioners operate on similar principles, but per their name are inserted into a window and vent the warmer air directly out the backside of the unit.
Window ACs can be much cheaper than whole-home systems, but they are only designed to cool small spaces. They are also notoriously loud at times and are less efficient than other options available to homeowners.
Floor or Wall-Mounted ACs
You probably see these most often in hotel rooms, where a floor or wall-mounted unit is pressed against the far side of the room, and controls for it exist on top of the cooling vents.
These are an upgrade in efficiency and sizing compared to window units but suffer many of the same limitations. Installing multiple floor or wall-mounted units to cover a whole home is usually prohibitively expensive.
Portable Air Conditioner
These are slightly more flexible versions of window-mounted ACs. They usually exist as a tower that absorbs heat and recirculates cool air, and have a large tube that connects to a nearby window or similar outlet.
This tube is sort of like a miniature duct line, and they’re often similarly constructed and insulated. But the limitations should be obvious. The most powerful portable air conditioners can handle medium-sized spaces but are inadequate for entire homes.
Geothermal Air Conditioners
Geothermal ACs utilize ground temperature – which is consistent year-round just a handful of feet below the surface, to regulate the temperature in your home.
Unlike some of the options just above, geothermal can indeed cool your entire home, and it can be extremely efficient energy as well.
The issue is the upfront cost, and maintenance costs should anything go wrong. The installation requires a lot of complicated work, and there aren’t many contractors licensed to do this work. The cost can be tens of thousands more than a traditional central air conditioning system.
The tradeoff is in long-term energy savings, eco-friendly energy, and the ability to cool large homes efficiently.
Evaporative Coolers (aka Swamp Coolers)
These operate on a different cooling principle. Whereas traditional ACs remove humidity, evaporative coolers evaporate and distribute moisture, adding humidity while also cooling.
Besides only being useful for individual rooms or small spaces, swamp coolers make the most sense in dry climates. In areas where it’s already very humid, they can struggle to provide comfort in the way that other types will.
Ductless Mini-Split Air Conditioners
Ductless ACs work almost identically to central air ACs, but as the name implies, they do so without ductwork. However, an individual line is run to a secondary unit outside the home where warm air is vented.
Ductless mini-splits are more expensive than standalone cooler and window units, but they’re also a lot more efficient and can often cover larger spaces.
They can be ideal for cooling out-of-the-way spaces such as master bedrooms, finished basements and attics, guest bedrooms, and home additions that aren’t connected to the preexisting home’s ductwork.
Parts of a Central Air Conditioner
- Blower Motor – the motor and fan that circulates air through your ductwork and over the evaporator coil, allowing it to absorb heat from the ambient air in your home before being recirculated.
- Compressor – located in the outdoor AC unit, the compressor turns the refrigerant into a liquid, allowing it to expel heat.
- Condenser Coil – also located outside, this works in conjunction with the compressor to change the state of the refrigerant so it can be vented outside the home.
- Ductwork – the veins of your system, so to speak, with the airflow being the blood running through them. Without properly sized and sealed ductwork, the rest of the system can’t do its job.
- Evaporator Coil – located in the indoor cooling unit, the coil absorbs moisture and heat from the air flowing over it to be taken outside the home, cooling the air in the process.
- Filter – we sometimes think of a filter as synonymous with a furnace, but air flows through your filter any time your HVAC system is running. The filter is crucial to maintaining airflow and air quality while cooling.
- Liquid Line – paired with the suction line, this is tubing that connects your indoor and outdoor AC units and houses the refrigerant when it’s in its liquid form.
- Refrigerant – the substance that allows the air conditioner to absorb and expel heat. If you have a refrigerant leak, your system will be much less efficient and will eventually stop working entirely.
- Suction Line – if the liquid line houses refrigerant when it’s a liquid, the suction line is for when it’s in gas form, taking it between the indoor and outdoor units.
- Thermostat – like ductwork, we don’t always think of thermostats as part of an air conditioner, but they control ALL heating and cooling functions. Without a properly connected thermostat, you lack the ability to control your home’s temperature.
Air Conditioner Efficiency
Not all air conditioners are created equal. This is true in a few different ways.
We’ve talked about HVAC brands before, and while we’re of the mind that the installation is more important than the brand, it’s true that the make and model of your AC can determine things like:
- Noise level
- Physical size
- Features like smart thermostats and app integration
- Efficiency
Focusing on the last of those, efficiency is often the most important feature of an air conditioner for homeowners, because it relates directly to cost savings and comfort.
SEER stands for Seasonal Energy Efficiency Ratio. It’s a measure of air conditioner efficiency. In recent years, a SEER2 rating is being used by most manufacturers as well. This is a similar rating that’s simply an evolution of the original SEER rating, one that is slightly more accurate across a wider array of climate conditions.
Higher SEER is better, though your expected cost savings will depend on how much you use your system and how large an upgrade it is over your current system.
To get a better estimate of cost savings based on SEER rating, you can talk to a trusted cooling rep who will be able to better estimate cost savings based on your specific situation.
Single-Stage, Two Stage and Variable Speed ACs
The other way air conditioners contribute to efficiency is through staging. Broadly speaking, there are three types of air conditioners:
- Single Stage – these are either 100% on or off.
- Two-Stage ACs – these have a second setting, usually 60% or 70% power.
- Variable Speed ACs – these can have a few settings all the way up to hundreds of different stages.
The lower settings of those last two types allow for a more even cooling environment throughout your home, and they also use less energy. It may seem weird, but sometimes having your air conditioner on for longer can actually use less energy, provided it’s at a lower power setting.
By adjusting this power level to the needs of your home, multi-stage equipment is able to provide efficiency gains and comfort gains for your home.
BTUs and Tonnage: Air Conditioner Capacity
Here’s another technical idea that initially seems like only your contractor needs to know about it, but we’ll explain why it should matter to you as well.
BTUs, or British Thermal Units, is a measurement of energy, and in this case relates to how much heating and cooling energy your system can provide to your home.
Different homes require different BTU amounts. A 600-foot studio apartment has less cooling needs than a 3,000 square foot home.
Tonnage is another industry term that’s measured in BTUs. One ton equals 12,000 BTUs. You’ll often hear this term when selecting a unit. “Your current system is a 3-ton system,” they might say, “so that’s the size we’ll replace it with.”
Size, power, capacity…for our purposes, these mean largely the same thing. It’s measuring the output of your air conditioner as it relates to the needs of your home.
Here’s why it matters for you: Your old system’s tonnage is not necessarily correct. The correct way to measure for home energy needs is something called a Manual J Load Calculation, which takes into account things like number of windows, square footage, insulation, ceiling height, relation of the windows to the sun, and more.
Just “eyeballing” the size can lead to mis-sizing of your AC unit, and you end up with something that is improperly sized for your home and thus inefficient.
Holding your HVAC company accountable for this is an easy step to ensure you’re getting the best air conditioner for your home.
Your Home Air Conditioning System
Them’s the basics of air conditioning. If you’ve read this far, congratulations! You hopefully know a lot more about the cooling in your home.
What’s next? Well, I’m guessing you didn’t read all of this just from academic interest. And if you did, I hope this helps on your book report!
But seriously, it’s likely you’re in the market for a new air conditioner, and so the next step is to reach out to a trusted HVAC specialist who can give you options and pricing for a variety of home systems catered to your specific needs.
If you’re in the Sacramento, CA area, we hope your first call is to us! We’ve helped thousands of homeowners to feel more comfortable and confident in their homes all year long, both cooling and heating. We can’t wait to help you next!
