How Does Central Air Conditioning Work?

You know how when you start to feel a bit uncomfortable, and you click on that thermostat, that cool air surges out of your vents, and your home starts to feel cooler almost immediately? But how does the air conditioning process actually work? In this article, we’ll explain how an air conditioner works so you can impress your friends at dinner parties with your new knowledge.

Actually, a basic knowledge of how your air conditioning works will give you a better understanding if you ever need to troubleshoot it, and just to have a better understanding of how your home operates.

How Does an Air Conditioner Work?

Central air conditioning systems work on the principles of refrigeration—which is why many people here in New Mexico call air conditioning “refrigerated air.” Air conditioners cool indoor air by removing heat from it and moving that heat outside. The process uses four main components:

  • Compressor
  • Condenser
  • Expansion valve
  • Evaporator

An air conditioning system works by taking warm air inside your home and sending it outside. A gas called refrigerant absorbs heat, and this substance can easily switch between gas and liquid form, allowing it to move through air conditioning systems. (We talked all about the difference between refrigerant and the cooling methods that swamp coolers use in a recent blog if you’re interested.)

The refrigerant is pumped through a series of pipes and coils by a machine called a compressor. When it enters the condenser, which is the part of your AC unit that is located outside your home, it gives off the heat that was captured inside the home, which is then released into the air.

After the refrigerant releases its heat, it travels back inside your home through the expansion valve, where it turns back into a gas and gets very cold. Then, the cold gas passes through a coil called the evaporator, which is located inside your home along with your furnace, and helps to absorb heat from the air already inside the home. The cool air created by the evaporator circulates throughout your home by a fan in the air handler.

As we already mentioned, you control the temperature in your home with the thermostat, which tells the AC system when to turn on and off. When it gets too hot inside, the thermostat signals the AC to turn on and start the process all over again to get the home to the desired temperature.

With a central air conditioner, the same air is recirculated through the home again and again. This is why some people take additional measures to help with indoor air quality, like installing an air purifier.

How is Central Air Conditioning Different than a Ductless System?

Ductless systems are a popular way to cool a home if you live in an older home that doesn’t have ducting. Ductless systems are also called mini-splits. In a traditional air conditioning unit, the warm air is cooled via the refrigerant, and carried back into the various rooms in your home through the duct system. Cooled air comes out of the registers located in each room in your home. Air is pulled back into the system through the air return vent.

In a ductless system, there is no ducting for the air to move through. But, the air is cooled with the same cooling process as a traditional air conditioner, with the condenser, evaporator coil, refrigerant, etc., that we just described.

The main difference is that in a ductless system, the only thing moving between the indoor and outdoor units is the refrigerant, which lets off heat in the condenser outside and is cooled off in the compressor inside. Air does not move through ducts in the home, rather it is pulled in and pushed back out of the same indoor units.

One outdoor unit can control multiple indoor units for whole-home cooling. Or you can install just one outdoor unit and one indoor unit to control the temperature in one room that gets overheated in a home that already has a ducted air conditioning system.

How Do I Know the Air Conditioner is Working Correctly?

If your air conditioning system works correctly, your home will be cool and at the temperature you set on the thermostat.

Other things to look for are the age of your system and if you get it maintenanced regularly. If you have regular maintenance, your AC is less than 15-20 years old, and it seems to be functioning well, there’s no reason to think that it’s not.

But you should contact an HVAC specialist for possible repair or replacement if:

  • Your AC is reaching the end of its lifespan
  • You keep hearing it cycling off and on, but it’s not cooling the home
  • There are loud, sudden, or unusual noises
  • There are unusual smells (other than the first use of the season)
  • Your home isn’t cooling off/the unit is blowing warm air

What’s the Right-Sized AC System for My Home to Have Cold Air?

If you’re installing a new air conditioning system in your home or just wondering if the one you have is doing the trick, here are some guidelines for how to choose the right-sized air conditioner for your home. Also, a trained HVAC specialist should be able to give you a more personalized idea if they come out to your home for an estimate.

Air Conditioner Equation

The size of air conditioners are measured in BTUs or British Thermal Unit, and that measurement refers to how much energy it takes to remove heat from the air.

If you like crunching numbers, here’s what you need to do. Measure the square footage of each room by multiplying the length and the width of the room. Then take that number and multiply it by 25 BTU, and that’s the size of the air conditioning system you need.

Here’s an example, and we will use just one room for the sake of simplicity.

If your room is 11 feet by 14 feet, then do the equation:

11x14x25BTU=3,850 BTU

What Kind of Maintenance is Required for Central Air?

Many people, unfortunately, don’t realize that they need to have regular maintenance performed on their AC, which results in unnecessary cooling outages and costly repairs. But, with yearly maintenance for your air conditioner, you can prevent both of those things.

Maintenance Steps for Air Conditioners

In a maintenance appointment, an HVAC tech will work through a comprehensive checklist to ensure your air conditioner is ready to serve you all summer. Springtime is the best time to have maintenance performed. Some of the things a tech will do at a maintenance appointment are:

  • They’ll make sure the coils are clear of any buildup.
  • Your tech will clean the exterior of the condenser unit and make sure there aren’t any leaves, cottonwood seeds, and any other debris.
  • The tech will cycle the AC system and check the temperature of the air coming out of the supply duct and the air going back into the return ducts.
  • Test electrical connections and look for burn marks (a sign of a short).
  • Suggest any parts replacements or repairs they see fit to keep you cool all summer.

You’ll also need to replace your furnace filter every three months, which they can do for you at a maintenance appointment. You’ll need to do it yourself throughout the rest of the year.

How is Refrigerated Air Different than Evaporative Cooling?

Here in New Mexico, swamp coolers are popular, especially in older homes that don’t have ducting.

Swamp coolers are almost like a simpler version of central air conditioners. Instead of using refrigerant to cool the air like an air conditioner, an evaporative cooler works by air blowing past pads soaked with water. This system uses outside air, cools it, distributes the cooler air inside, and then excess air escapes with the help of the homeowner leaving a window cracked open.

There are certainly pros and cons to swamp coolers, but the top reasons why people like them are they are less expensive and more efficient than air conditioning, they add humidity to the air, which can be nice in our dry climate, and they bring fresh air into the home.

What’s the Best Cooling System for New Mexico?

You definitely have options when it comes to cooling your home, and a lot of it depends on the structure of your home, your goals for bills, and your preferences for aesthetics. However, for many people, traditional air conditioning makes the most sense.

A mini-split system air conditioner can be a great choice for a home with no ducting, but it’s also more expensive to install than central AC. And swamp coolers can be more cost-effective and energy-efficient, but they also don’t cool homes to a comfortable temperature during the hottest times of the summer. They’re limited to cooling the home to about 20 degrees less than the outside temp.

If you want a professional consultation to learn which cooling system would be ideal for your home and your cooling needs, give us a call at Bosque Heating, Cooling and Plumbing at (505)444-7200.

May 15



AC, AC installation, AC Maintenance, Air Conditioning, central air conditioning, central airconditioner

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