Every homeowner should have a basic understanding of their home's HVAC equipment. Knowing how your system works can help you recognize problems and understand when you'll need professional help, even if you don't plan to do any DIY maintenance or repairs. Fortunately, the essentials of a home HVAC system aren't too hard to learn.

The refrigerant cycle is a great place to start on your learning journey. Understanding the basics of how refrigerant keeps your home cool and why your system has a high and low-pressure side can help you understand a surprisingly large number of problems.

The Highway of Heat: Why You Need Refrigerant

You might be surprised to learn that air-conditioning is often drastically more efficient than heating. Most heating systems work by extracting through combustion or, in the case of electric heating, by utilizing waste energy generated by electrical resistance. On the other hand, your air conditioner does not produce energy; it simply moves it from place to place. This process is much more efficient.

Your air conditioner's refrigerant loop is a bit like a heat highway. The on-ramp is your evaporator coil, where the cold liquid refrigerant absorbs heat from inside your home. As the refrigerant heats up, it turns into a vapor and travels along the highway. The off-ramp is your outdoor compressor unit where the refrigerant can release its heat into the environment before starting the journey again.

Under Pressure: The Two Sides of Your AC System

The refrigerant highway relies on a pressure differential between the two sides of your system. The indoor side, which consists of your evaporator coil, air handler, and associated plumbing, is the low side. The outdoor portion of the system, which includes your condenser coils and compressor, is the high side.

The warm, vaporized refrigerant returns to the compressor from the low side. The compressor then drastically increases its pressure, turning it into a hot gas that quickly releases its heat into the environment as it passes through the condenser coils. These pressurized gases return through an orifice tube or thermal expansion valve (TXV) that lowers their pressure and turns them back to a cool liquid.

The entire system relies on a careful pressure balance between the high and low sides. Too much or too little pressure can cause numerous problems, including freezing the evaporator coils and preventing them from absorbing more heat. Interruptions in the refrigerant cycle can also allow liquid refrigerant to return to the compressor, potentially causing severe damage or even destroying it.

Unfortunately, there's no easy way to monitor your system's refrigerant pressure. Instead, it's crucial to pay attention to changes in your system's behavior. If you notice your AC rapidly turning off and on or find your home suddenly more humid, these may be signs of a refrigerant problem. Contacting an HVAC tech for support is your best option to resolve the issue and avoid causing more severe damage.