What Is Air Conditioner Refrigerant & How Does It Work

Air conditioner refrigerant is the magical substance that makes air conditioning possible. Its ability to quickly change states is what allows us to cool (or heat) our homes, offices, and commercial buildings, keeping us sweat-free and blissfully comfortable.

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In this article, we explore the science behind air conditioner refrigerants, and how it works as part of the air conditioner’s refrigeration cycle. We also delve into the most common refrigerant in Australia—R-32—and touch on how much refrigerant an AC system needs. Let’s jump in.

What is air conditioner refrigerant & how does it work?

Chlorofluorocarbon (CFC) air conditioner refrigerant was created by the American chemical company DuPont in 1928, as a replacement for the flammable and highly toxic substances used in fridges. CFC made fridges much safer, but unfortunately, was discovered to be a potent greenhouse gas, thousands of times more warming than CO2. It also eats away at the earth’s ozone layer, which prompted the development of hydrofluorocarbons (HFCs, branded as Freon)—a safer, more environmentally-friendly substance that is still used today.

There’s about ten types of refrigerant used in air conditioners today, but the most common for residential and commercial systems is R-32.

R-32 and other refrigerants are the lifeblood of air conditioners. They are the substance that allows the whole refrigeration process to work, due to their ability to quickly change states. During the refrigeration cycle, the substance changes from a cool liquid, a vapour, and hot gas, caused by pressure changes from the air conditioner’s components. The system uses these state/temperature changes to produce cool or hot air for a building.

The refrigeration cycle is complex and a little counterintuitive, but here’s a breakdown of how it works, including an accompanying diagram to help:

Original image from Torr Engineering

1. The refrigerant enters the compressor as a low-pressure, superheated gas.
2. The compressor pumps the gas towards the condenser, where it cools and condenses, turning into vapour and then a cool, high-pressure liquid. This process produces hot air, which the condenser (contained in the outside unit) blows away with a fan.
3. The liquid arrives at the metering device, which lowers its pressure and turns it back into a vapour.
4. The vapour enters the evaporator, where it absorbs heat from the space being cooled. This causes the vapour to boil, which turns it back into superheated low-pressure gas. This process produces cool air, which the AC unit’s fan blows into the room.
5. The gas enters the compressor, for the cycle to start over.

(Check out our Air Conditioning Vocab article if you’d like to learn more about these terms).

For those that remember basic chemistry, this might seem odd. How can refrigerant be both superheated and low-pressure? But this is the beauty of the substance—its unique chemical makeup gives it a boiling point and critical temperature that allows this to occur, which is why we’re blessed with fridges, freezes, and air conditioning.

R-32 has a lifespan of between seven and 17 years. If an air conditioner’s refrigerant levels are too low, a technician will need to top them up with the same type of refrigerant. If another type of refrigerant is used, the mixture is “contaminated” and may perform badly, as well as damage the air conditioner’s parts. Air conditioning technicians require a refrigerant handling licence (RHL) to buy and use R-32.

In Australia, dead refrigerant is sent to a plasma arc plant to be destroyed. This plant uses temperatures of 10,000°C to break down the fluorocarbon waste into safer acid gases,1 which don’t contribute to global warming.

These are some other common types of refrigerant still used today:

• R-717
• R-152a
• R-290 (propane)
• R-407c
• R-410a
• R-744
• HFO-1234yf
• R-134a
• R-454B

How much refrigerant is in a home air conditioner?

The amount of refrigerant in a home air conditioner depends on the size of the system, the length of copper line, and the size of the evaporator coil, so there’s no simple answer here. You can use this general rule of thumb though: an AC system requires 2-4 pounds per ton of cooling. So if your system provides 2-ton of cooling, it will require between 4-8 pounds of refrigerant3.

What is R32 refrigerant?

R-32 is a hydrofluorocarbon substance, made up of two hydrocarbon molecules and two fluorine molecules, which create a structure that looks like a plus symbol. It’s colourless, odorless, and efficiently carries heat, has a low flammability score, and a high operating pressure, which is why it’s become one of the most commonly used refrigerants for Australian air conditioners, used in around 71% of the residential and commercial market2.

R-32 has a global warming potential of 675, which means that it’s 675 times more potent than CO2. By comparison, one of the worst “R” DuPont refrigerants has a GWP of 14,800, so R-32 remains an environmentally-friendly choice. It’s also completely ozone-friendly, unlike the earlier chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) substances. Here’s the environmental impact of R-32’s compared against other common refrigerants:

Image from Daikin

Here are the technical properties of R-32:

Boiling point

-51.7°C

Critical temperature

78.4°C

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Saturation pressure at 4°C

818kPa

Saturation pressure at 4°C

2380kPa

Flammability rating

A2L (lower flammability)

Air conditioner refrigerant leak symptoms

Refrigerant leaks can happen for a variety of reasons. The technician’s process may be sloppy when they’re adding, removing, or topping the refrigerant up, the copper pipe that holds the refrigerant may corrode and erode over time, or there may be a factory defect in the AC system itself.

Large refrigerant leaks are a concern, because when inhaled, refrigerant cuts off your oxygen supply. When inhaled in large amounts, this can kill you4.

Thankfully, there’s plenty of signs of refrigerant leaks that can alert you to a leak:

• The system’s airflow seems low, because it can’t produce as much cool air as usual. This causes your property to cool down much more slowly.
• The system is blowing warm air instead of cool air.
• There’s a hissing sound coming from the indoor unit.
• You have unusually high electric bills, which arrive consistently.

If you’d like to learn more about potential problems with your system, check out our guide on Air Conditioning Troubleshooting.

Summary

Refrigerant is an extraordinary substance that has allowed us to accurately regulate the temperature of our homes, and preserve our food in fridges and freezers. With the creation of R-32, and the continued development of better refrigerants, we’re keeping our precious lifestyle while helping to mitigate global warming.

We hope this article has been useful. Thanks for reading!

References

Air conditioners use refrigeration to chill indoor air, taking advantage of a remarkable physical law: When a liquid converts to a gas (in a process called phase conversion), it absorbs heat. Air conditioners exploit this feature of phase conversion by forcing special chemical compounds to evaporate and condense over and over again in a closed system of coils.

The compounds involved are refrigerants that have properties enabling them to change at relatively low temperatures. Air conditioners also contain fans that move warm interior air over these cold, refrigerant-filled coils. In fact, central air conditioners have a whole system of ducts designed to funnel air to and from these serpentine, air-chilling coils.

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When hot air flows over the cold, low-pressure evaporator coils, the refrigerant inside absorbs heat as it changes from a liquid to a gaseous state. To keep cooling efficiently, the air conditioner has to convert the refrigerant gas back to a liquid again. To do that, a compressor puts the gas under high pressure, a process that creates unwanted heat. All the extra heat created by compressing the gas is then evacuated to the outdoors with the help of a second set of coils called condenser coils, and a second fan. As the gas cools, it changes back to a liquid, and the process starts all over again. Think of it as an endless, elegant cycle: liquid refrigerant, phase conversion to a gas/ heat absorption, compression and phase transition back to a liquid again.

It's easy to see that there are two distinct things going on in an air conditioner. Refrigerant is chilling the indoor air, and the resulting gas is being continually compressed and cooled for conversion back to a liquid again. On the next page, we'll look at how the different parts of an air conditioner work to make all that possible.

Cool the Green Way

The chemical composition of modern refrigerant compounds has changed over the last few decades as a result of environmental concerns and international treaty agreements like the Montreal Protocol. Older refrigerant formulas containing chlorine atoms that had the potential to damage the ozone layer have slowly been phased out in favor of more environmentally friendly coolants [source: EPA].

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