AC Liquid Line – What Is It & How Does It Work?

Air conditioners consist of several components, and the liquid line is one of the crucial ones. However, most people are not familiar with it.

If you are one of those people who want to know more about AC liquid lines, you have come to the right place. I will walk you through what it is, its purpose, its functionality, and how to maintain it so you’ll have everything you need to know at your fingertip.

So, keep reading! 

What is an AC liquid line?

what is ac liquid line

As the name suggests, the AC liquid line (also known as the HVAC liquid line) is the small refrigerant line responsible for carrying liquid refrigerant from the condenser to the expansion valve. It is made of copper, warm, and usually not insulated.

As a side note, there is the other type of refrigerant line – the suction line, which connects the evaporator to the compressor, is larger, colder, and easily confused with the liquid line.

How does an AC liquid line work?

how does ac liquid line work

The refrigerant absorbs heat when changing from liquid to gas and releases heat when changing from gas to liquid. This is what the refrigeration cycle is. Air conditioners make use of it so as to pull heat indoors out of your house.

As you may know, a condenser is where the gaseous refrigerant turns into liquid, and the heat is released. Once this is done, the refrigerant needs to be sent to the indoor un. After that, it will take away the heat in the room when passing through the evaporator coil. 

But there is a small part between the condenser and the evaporator: the expansion valve. This valve could convert the refrigerant from warm and high-pressured to cold and low-pressured, creating a good condition for absorbing heat later on. 

The AC liquid line is the copper pipe in charge of sending the liquid refrigerant from the condenser to the expansion valve.

The temperature of AC liquid line

Contrary to the suction line, the liquid line is warm to the touch. This is because the compressor will heat the refrigerant to a high temperature.

Even though the refrigerant has released part of its heat when passing through the condenser, it still has a relatively high temperature when entering the liquid line.

Typically, the temperature should be around 5 to 15 degrees Fahrenheit above the ambient. That’s why the liquid line is not insulated in most cases.

If it gets cold or extremely hot, it may mean something wrong with your AC.

Is the liquid line the high side?

Yes. The liquid line is the high side.

The compressor adds pressure to the refrigerant. So the refrigerant coming out of the compressor is under high pressure.

While the refrigerant will turn to liquid when going through the condenser, the pressure will not change much. Therefore, the refrigerant pressure in the liquid line will remain high.

How long do HVAC liquid lines last?

Liquid lines can last for a long time, ranging from 10 to more than 25 years.

Nevertheless, many factors affect its lifespan. For example, the liquid line exposed to extreme weather will last much shorter than the one in mild weather conditions.

Except, the material it is made of also matters. Some thin tube is prone to breaking. 

What happens if the AC liquid line fails?

The most common problem that happens in AC liquid lines is refrigerant leaks. When the refrigerant level drops, it will cause the evaporator coil to freeze, affecting the cooling performance.

Then the compressor needs to work hard to take away more heat. In the end, the compressor will overheat. That’s one of the reasons why your AC is running but not cooling.

To solve this problem, you should either fix the leak or replace the entire liquid line. After that, the refrigerant should be recharged.

It is worth mentioning that you should leave this task to a certified HVAC expert since the refrigerant is hazardous and is not allowed to be tackled by ourselves.

How to maintain an AC liquid line?

If you want to extend your liquid lines’ lifespan, you should commit to regular maintenance. 

The liquid line will vibrate when working. Therefore, you should add some insulation where the line meets the wall.

At the beginning of each cooling season, you should hire a pro to check its state and test the refrigerant pressure so that the leaks can be discovered in the initial stage, saving you a bunch of money on repairing.

Sum up 

If you are not tech-savvy, chances are you don’t really know what an AC liquid line is. Basically, it is the copper tube that carries refrigerant from the condenser to the expansion thermal expansion valve. 

The refrigerant inside is warm and high-pressurized, and the pipe itself is smaller than the suction line. 

Usually, it is not insulated because it needs to shed heat. Luckily, it is long-lasting. But when it breaks, it can cause the compressor to overheat or even fail. It should be checked regularly to avoid any expensive repairs. 

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Liz Yang is the founder of Airsmartly. She has been working at home for a few years and realizes that the performance of the HVAC system plays such an important role in our life. She has tested a lot of products in person, like humidifiers, air purifiers, dehumidifiers, and ACs, and wants to share tips about using or troubleshooting these products with you. Her uncle is an HVAC expert with over 30 years of experience in the field, and often offers assistance when she is unsure how to handle a situation. He is also in charge of reviewing the articles on this site.