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If you own an air conditioner or heat pump, you’re likely aware it contains a sealed refrigerant system. However, you may not understand what role this coolant plays in HVAC function. They’re at the heart of how ACs and heat pumps operate. Here’s everything you need to know about refrigerants and their role in HVAC function.
What Is a Refrigerant?
A refrigerant is a working fluid that HVAC systems use to capture, move, and expel heat. These fluids are chemical compounds that easily change temperature as they transition between liquid and gaseous states. Air conditioners and heat pumps manipulate the pressure and temperature of their refrigerants to transport heat. That process is called the refrigeration cycle.
What Is the Refrigeration Cycle?
The refrigeration cycle inside an AC begins when your thermostat activates the cooling system. That triggers multiple processes. One is activating the blower motor in the indoor air handler and the large fan in the outdoor condenser. It also includes turning on the compressor, which functions like a pump to circulate the refrigerant.
To begin the cooling process, the AC passes its liquid refrigerant through an expansion valve. That lowers the pressure on the refrigerant. As that happens, the temperature and boiling point of this coolant drop. Next, the now-cold refrigerant moves into the evaporator coil inside the indoor unit. There, the blower fan draws in hot air from your home and pushes it through the heat transfer fins in the coils. Since heat energy moves from hotter to colder substances, the air cools, and the refrigerant warms up. When the refrigerant absorbs enough heat, it boils into a warm gas. The blower keeps running to push the now-cold air into your home.
The warm gaseous refrigerant then moves back outside to the condenser unit in the AC. There, it enters the compressor, which increases its pressure and temperature. Upon leaving the compressor, the refrigerant will be between 120 and 140 degrees. That’s hotter than the ambient air, even on the hottest summer day. As a result, the refrigerant will readily release its heat outdoors.
The next stage of the refrigeration cycle happens when the hot gaseous refrigerant enters the condenser coil. As it does, the large fan in the outdoor unit pulls air through the coil and vents it out of the top. That lets the air extract heat from the hot refrigerant until it changes phases back into a warm liquid. From there, the process repeats for as long as your home requires cooling.
How Heat Pumps Use the Refrigeration Cycle
In cooling mode, heat pumps operate identically to an air conditioner. However, they contain some extra equipment that makes them capable of running in reverse. That’s why they can also serve as a heating solution for your home. A reversing valve is the most essential component distinguishing a heat pump from an AC. It is a device that can redirect refrigerant flows based on electrical impulses. Heat pumps also have two expansion valves. One resides in their outdoor unit, just like an AC, and the other is in their indoor unit. The second valve only operates when the heat pump runs in heat mode.
Although it may sound unusual, heat pumps use the refrigeration cycle to extract heat from the outdoor air. That’s possible as long as the refrigerant can get colder than the outside air. The greater the temperature differential between the refrigerant and the outside air, the more efficiently the heat pump operates. Modern heat pump refrigerants can extract heat from the outside air down to -15 degrees and below. Theoretically, it’s possible for heat pumps to work at temperatures down to −459.67 degrees, which is absolute zero. At that point, the air would have no heat energy stored in it. However, refrigerants capable of that temperature performance are unlikely ever to exist.
Common Refrigerant Types
Various air conditioning and refrigeration solutions have relied on refrigerants since the 1800s. The earliest systems used substances like ammonia, propane, sulfur dioxide, and methyl chloride. The problem is that those substances were toxic, flammable, or both. That made their use hazardous. As a result, scientists and engineers developed newer, safer refrigerants for use in subsequent systems.
Chlorofluorocarbon Refrigerants
One of the first non-flammable and minimally toxic refrigerants was a substance called R-12. It was a chlorofluorocarbon (CFC), meaning it contained chlorine, fluorine, and carbon atoms. It first came to market in 1928 and sold under the trade name Freon-12. Soon thereafter, R-22 became the most popular refrigerant in residential and commercial HVAC systems. It remained popular until the late 1980s when scientists discovered it contributed to atmospheric ozone depletion. Today, R-12 is illegal to produce almost everywhere in the world. However, some older HVAC systems are still using it, although servicing such systems is growing harder.
Hydrochlorofluorocarbon Refrigerants
As part of the phase-out of CFCs globally, a new class of refrigerants evolved to take their place. Known as hydrochlorofluorocarbons (HCFCs), they had far lower ozone depletion potential. They consist of hydrogen, chlorine, fluorine, and carbon atoms. HCFCs are more unstable than CFCs, allowing them to break down before reaching Earth’s ozone layer upon release. One of the most popular HCFCs was R-22. Unfortunately, while moderately safer for the ozone layer, HCFCs still proved potent as greenhouse gases. As a result, they, too, faced a mandatory phase-out beginning in 2010. In developed countries, HCFCs became illegal to produce as of 2020. Major HVAC manufacturers, however, stopped using them well before then.
Hydrofluorocarbon Refrigerants
The most common refrigerant that replaced CFCs and HCFCs in HVAC systems was R-410A. It is a hydrofluorocarbon (HFC) comprising hydrogen, fluorine, and carbon atoms. The omission of chlorine makes HFCs completely ozone-safe, although they remain a greenhouse gas. Nevertheless, most HVAC systems installed and running today use R-410A. To address that weakness, most manufacturers are already transitioning to other HFCs.
Newer HFCs include R-32, which has already gained significant market share. Another popular alternative is R-454B, which is technically a blend of an HFC and another substance called a hydrofluoroolefin (HFO). Both have dramatically lower global warming potential. Regardless, HFCs also face a mandatory phase-out. At the time of this writing, it’s unclear what will replace them; however, HFOs are already leading candidates.
Your Local HVAC Experts
Atticman Heating and Air Conditioning, Insulation is the HVAC expert to turn to in Sacramento, CA. We offer complete HVAC installation, repair, and maintenance services. Our maintenance plan for HVAC is called The Cool Club! We also provide ductwork, whole-house fans, insulation, and water heaters. We’ve served local homeowners for over six years, building an impressive reputation in that time. We’re Better Business Bureau accredited with an A+ rating and have countless glowing customer reviews. We even offer financing on approved credit for new HVAC systems should you need help paying for one. So, when you need HVAC services for your Sacramento home, contact our team at Atticman Heating and Air Conditioning, Insulation immediately!
