It doesn’t take a lot of complicated machinery to generate heat. Rub two sticks together fast enough, and you have a fire that can warm an entire room. Even a home furnace system works on basic principles: Heat source, fan, ducts.

Creating cool air, however, is more complicated. An air conditioning (A/C) system requires a cooling fluid, a condenser, an evaporator, a fan… certainly not something you can accomplish with two sticks and a wilderness manual.

In the Central Air Close-Up series, we’ll look at specific parts of the A/C system—what they are, what they do and how to keep them maintained. For this one, we’re looking at the suction line and suction line insulation.

What You Need to Know about Suction Line Insulation

Before we dive into how the suction line works, here’s a quick refresher on how a central air system functions:

1. In the internal air handler, warm indoor air is blown across coils that are full of cold refrigerant.
2. The refrigerant absorbs heat from the air.
3. This heats up the refrigerant, turning it from liquid to gas.
4. The cooled air is distributed back to the home.
5. The hot refrigerant is pumped to the outside unit.
6. The outdoor unit compresses the gas, raising its temperature even higher.
7. Coils of piping radiate the heat into the air outdoors.
8. The refrigerant cools and returns to liquid form.
9. Refrigerant is piped back into the house to start the process again.

What is the suction line?

The A/C suction line carries heated refrigerant in gas form from the internal unit to the external, where the gas can be cooled and compressed back down into liquid. 

The other part of the loop is called the liquid line, and it transfers the cooled refrigerant, in liquid form, back into the interior of the house.

Why is the suction line important?

If your suction line isn’t working properly, it can’t do its part in the cycle of warming and cooling the refrigerant. The entire air conditioning process needs both the suction line and the liquid line in order to function.

Why do I need suction line insulation?

Remember, the suction line is carrying the heat from your home, absorbed into the gaseous refrigerant. Suction line insulation keeps that heat from being transferred to the compressor. 

As such, the insulation is important to the long-term health of your A/C unit. When the compressor has to deal with increased heat, it has to work harder. That means it uses more energy and burns out faster. 

In short, suction line insulation is a small part of your A/C system, one that can be cheaply inspected and repaired. But if it’s neglected, it can lead to a breakdown in the compressor itself, requiring a much more costly repair or even replacement.

How can I make sure my A/C unit is properly insulated?

Before you turn on your A/C unit for the summer, it’s a good idea to schedule a maintenance visit. An HVAC professional can check all the components of your system, including the liquid and suction lines. 

In addition to making sure the refrigerant loop is working properly, the maintenance tech will: 

• Clean condenser coils
• Clean the outdoor condenser unit
• Check condensate drains
• Check refrigerant levels
• Check for refrigerant leaks
• Inspect electric components
• Oil motor components
• Check belts for tightness and wear
• Check for broken and worn out components
• Check your thermostat

Still have questions about your air conditioner? Check out the five most common air condition repair questions and answers.