3 Prevention Tips for Frozen Suction Lines


It’s not uncommon for ACs to freeze even in the midst of summer if you happen to skip routine maintenance. A frozen suction line can stem from several issues. Regardless of the cause, the frozen lines would render the system useless. You might have discovered the frozen lines by chance while examining what possibly went wrong. 

So, it would be logical to sort the issue out by working with one of the reputed HVAC contractors like Hurliman. If you are not that tech-savvy, this post will tell you everything about suction lines.

However, you need to hire an established HVAC technician to get the system inspected. Ignoring the issue can lead to financial drainage on expensive repairs.

What is the suction line in your AC? 

In ACs, you have two copper lines connecting the outdoor heat pump and the indoor evaporator coil. The larger tube with insulation is the suction line. This line is responsible for carrying cool gas to the outdoor compressor from the indoor evaporator under low pressure. The terms vapor line or return line also refer to this suction line.

The other line does not have any insulation and is smaller. It carries hot fluid to the evaporator from the condenser under high pressure. 

What causes the supply line of your AC to freeze?

The suction line of your AC might freeze due to several factors. Let’s understand what might cause the suction line to freeze in the first place.

1. Issues with the airflow

The lack of regular maintenance can lead to the accumulation of dirt on the filter. At one stage, it blocks the airflow to the evaporator coil. The heat fails to reach the coil due to the lack of airflow. Therefore, the refrigerant doesn’t boil. The system tends to freeze due to a drop in temperature and pressure.

This can also happen in case you are using an excessively restrictive filter. In such cases, HVAC experts would recommend you get a better one.

The blower motor might run at a low speed or stop functioning altogether if the bearing wears out. The motor might blow up due to an electrical snag. Also, the board might not supply adequate power. As a result, the evaporator coil would receive less air. The longer your AC functions without the motor, the greater would be the accumulation of ice on the suction line. The unit might freeze due to any sort of obstruction of airflow to the evaporator coil.

2. Low refrigerant level 

The refrigerant present in your AC transforms to liquid from gas as it works to maintain the desired temperature in the home. As it absorbs heat, it changes from gas to liquid. Liquid has high pressure, while gas has low pressure. Therefore, the liquid having high pressure travels outdoors. Here, the fan blows heated air, so the fluid turns into gas having low pressure.

Throughout the AC’s life, the refrigerant volume remains the same. However, if the system leaks, it might diminish. As a result, there would be a reduction in pressure in the copper tubes in the system. Unless you hire HVAC experts to fix the leak, it would be futile to add fresh refrigerants.

With low refrigerant levels, its temperature would be low at the beginning of the coil compared to the freezing point. As a result of this low temperature, the condensation would freeze inside the coil. The flow of air through the coil would encounter obstruction due to the buildup of ice on the coil. So, the refrigerant won’t be able to absorb heat and start boiling in the coil. As a result, it would intensify the freezing, affecting the suction line.

3. Low temperature

If the temperature in your home dips below 70 degrees Fahrenheit, there would also be a drop in the saturation temperature. Again, when it dips below 32 degrees Fahrenheit, the suction lines would freeze. This can happen in case you have set the thermostat unusually low. In most homes, people set the thermostat above 67 degrees Fahrenheit. In case you go below this level, the suction lines might freeze.

Frozen Suction Lines

How to prevent your suction lines from freezing?

The most effective way to prevent your suction lines from freezing is to carry out regular maintenance. You can keep your system in good shape with routine maintenance from a trusted HVAC contractor. Here are some of the other ways in which you can prevent the lines from freezing.

1. Inspect for clogged vents

It makes sense to check the system for blocked return or supply vents. Supply vents are responsible for circulating cool air in your house. Any clog in this vent can cause low air flow and amount to issues in heat exchange. Therefore, you need to open the vents even in rooms you are not using. This way, you can thaw the coils which are currently frozen. Repeat the process with the return vents. This would let the evaporator coils get more warm air.

2. Switch to fan mode

Turn the compressor off and switch to the fan mode. This way, the AC would get enough time to cool off as the warm air in the surroundings would circulate through it. After four hours, you can restart the AC. Now, if the suction lines freeze again, you need to reach out to one of the established HVAC companies.

3. Replace the air filter

Your HVAC system can sustain a lot of damage due to a blocked air filter. It can also lead to freezing issues in the suction line. Now, you need to inspect whether the filter is dirty and get it replaced. Remember, your AC would encounter airflow issues if the filter is clogged. This can trigger freezing issues in the suction lines.


Most issues with your HVAC system stem from the lack of routine maintenance. This explains why concerned homeowners reach out to reputed HVAC experts to ensure proper care for these systems. Professional hands and industry knowledge are a must to ensure a long lifeline for your AC. With timely maintenance, you can keep frozen suction line issues at bay.

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