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  • Writer's pictureKrystal Morrell

Top Reasons Your Commercial HVAC Coils Freeze in Summer and How to Prevent It

Technician Repairing AC Unit


As the summer heat intensifies, ensuring that your HVAC system functions efficiently becomes crucial for maintaining a comfortable and productive environment. However, one common yet often perplexing issue that businesses encounter during these hot months is the freezing of HVAC coils. This problem can disrupt operations, lead to costly repairs, and reduce the overall efficiency of your cooling system.

Understanding the reasons behind this phenomenon is essential for preventing it and ensuring the longevity and performance of your HVAC system. At Re-Coil Solutions, we specialize in high-quality commercial HVAC coils and have extensive experience in diagnosing and solving such issues. Our expertise enables us to provide valuable insights and effective solutions to help you keep your HVAC system running smoothly throughout the summer.

In this article, we will explore the most common reasons why HVAC coils freeze during the summer, from insufficient airflow to refrigerant leaks, and provide practical tips on how to address these issues. With our guidance, you can take proactive measures to prevent coil freezing and ensure your business remains cool and comfortable all season long.

Reasons Why HVAC Coils Freeze in Summer

1. Insufficient Airflow

Restricted airflow is one of the most common reasons for HVAC coils freezing during the summer. When airflow is insufficient, the evaporator coil does not receive enough warm air from the space it is cooling. This lack of warm air causes the coil to get too cold due to prolonged exposure to the refrigerant, resulting in the condensation on the coil freezing. Over time, this can lead to a complete freeze-up, hindering the system's ability to cool effectively and potentially causing damage. The most common causes of restricted airflow are dirty filters, blocked vents, and faulty fans.

  • Dirty Filters: Air filters trap dust, dirt, and other particles, preventing them from entering the HVAC system. Over time, these filters can become clogged, reducing the amount of air that can pass through. Regularly checking and replacing air filters is essential to maintain proper airflow.

  • Blocked Vents: Vents and registers can become blocked by office equipment, curtains, furniture, or other obstructions, restricting the airflow into the room. Ensuring that vents are open and unobstructed helps maintain adequate airflow throughout the system.

  • Faulty Fans: The blower fan is responsible for moving air over the evaporator coil. If the fan is not working correctly due to a mechanical failure or electrical issue, it can significantly reduce airflow, leading to coil freezing.

2. Low Refrigerant Levels

Low refrigerant levels are another common cause of HVAC coils freezing during the summer. The refrigerant in your HVAC system is responsible for absorbing heat from the indoor air and releasing it outside. When the refrigerant level is too low, the system cannot absorb enough heat, causing the evaporator coil to become excessively cold. This can lead to the condensation on the coil freezing, eventually resulting in a complete freeze-up that hinders the system's ability to cool effectively. The most common cause of low refrigerant levels are leaks and improper charging during installation.

  • Leaks: Refrigerant leaks are the most common cause of low refrigerant levels. These leaks can occur in various parts of the HVAC system, such as the evaporator coil, condenser coil, or refrigerant lines. Over time, even a small leak can significantly reduce the amount of refrigerant, leading to coil freezing.

  • Improper Charging During Installation: If the HVAC system was not properly charged with the correct amount of refrigerant during installation, it could lead to insufficient refrigerant levels from the start. This improper charging can cause the system to struggle with maintaining adequate cooling and increase the risk of coil freezing.

3. Dirty Coils

Maintaining clean coils is essential for the efficient operation of your HVAC system. Dirt and debris on the coils can significantly impact their performance, leading to various issues, including coil freezing. Understanding the importance of clean coils and taking proactive measures to keep them free of contaminants is crucial for preventing these problems.

The evaporator and condenser coils play a vital role in the heat exchange process of your HVAC system. The evaporator coil absorbs heat from the indoor air, while the condenser coil releases it outside. When dirt and debris accumulate on these coils, it creates an insulating layer that hinders their ability to transfer heat efficiently. This reduced heat transfer can lead to several issues, including increased energy consumption, reduced cooling capacity, and, ultimately, coil freezing.

How dirty coils reduce heat transfer and cause freezing:

  • Reduced Heat Absorption: When the evaporator coil is covered in dirt and debris, it cannot effectively absorb heat from the indoor air. This causes the coil to become colder than it should be, leading to the condensation on the coil freezing. Over time, this ice buildup can obstruct airflow and further reduce the system's cooling efficiency.

  • Increased Strain on the System: Dirty coils force the HVAC system to work harder to achieve the desired cooling levels. This increased strain can cause other components, such as the blower fan and compressor, to work overtime, leading to potential mechanical failures and further exacerbating the freezing issue.

  • Blocked Drainage: Accumulated dirt and debris can also clog the drainage system, preventing the proper removal of condensation. This can result in water pooling around the evaporator coil, which can freeze and contribute to the ice buildup.

4. Other Mechanical Failures

Beyond insufficient airflow, low refrigerant levels, and dirty coils, other mechanical failures can also lead to HVAC coil freezing. These issues can stem from various components within the HVAC system, each playing a crucial role in maintaining optimal performance. Identifying and addressing these mechanical problems promptly is essential to prevent coil freezing and ensure efficient system operation. Below is an overview of other potential mechanical issues:

  • Malfunctioning Fans: The blower fan and condenser fan are integral to maintaining proper airflow across the coils. If these fans are not operating correctly due to electrical faults, worn-out bearings, or motor failures, the reduced airflow can cause the evaporator coil to freeze. Regular inspection and timely replacement of faulty fans are crucial to prevent this issue.

  • Broken Blower Motors: The blower motor drives the blower fan, which circulates air through the system. A malfunctioning or broken blower motor can significantly reduce airflow, leading to insufficient heat absorption by the evaporator coil and subsequent freezing. Signs of a failing blower motor include strange noises, weak airflow, and frequent cycling of the HVAC system.

  • Thermostat Malfunctions: A faulty thermostat can cause the HVAC system to run excessively or not enough, disrupting the balance needed for proper operation. Incorrect temperature readings or settings can lead to the evaporator coil becoming too cold and freezing. Ensuring that the thermostat is calibrated and functioning correctly is vital for preventing such issues.

  • Defective Expansion Valves: The expansion valve controls the flow of refrigerant into the evaporator coil. If this valve is not working correctly, it can either restrict the refrigerant flow or allow too much refrigerant to pass, both of which can cause the coil to freeze. Regular checks and maintenance of the expansion valve can help avoid this problem.

Solutions and Preventative Measures

1. Regular Maintenance

Regular maintenance checks are crucial for identifying and addressing potential issues before they escalate. Scheduled inspections help ensure that all components of the HVAC system are functioning correctly, preventing problems like coil freezing.

Key Maintenance Tasks to Prevent Coil Freezing:

  • Cleaning and Replacing Air Filters: Ensure air filters are clean and replaced regularly to maintain proper airflow.

  • Inspecting and Cleaning Coils: Regularly clean the evaporator and condenser coils to prevent dirt and debris buildup.

  • Checking Refrigerant Levels: Verify that refrigerant levels are adequate and inspect for any leaks.

  • Inspecting Fans and Blower Motors: Ensure that fans and blower motors are functioning correctly and are free from obstructions.

2. Proper Installation and Setup

Proper installation is critical to the long-term performance of your HVAC system. Incorrect installation can lead to various problems, including coil freezing, reduced efficiency, and premature system failure.

Hiring certified professionals ensures that your HVAC system is installed correctly and meets all necessary standards. Professionals have the expertise to set up the system for optimal performance and can provide valuable advice on maintaining it.

3. DIY Checks and Maintenance

Simple Maintenance Tasks Business Owners Can Perform:

  • Regularly Inspect Air Filters: Check and replace air filters as needed to ensure proper airflow.

  • Clear Obstructions Around Vents and Units: Ensure that vents and outdoor units are free from obstructions to maintain efficient airflow.

  • Monitor Thermostat Settings: Regularly check thermostat settings and calibrate if necessary.

When to Call a Professional for More Complex Issues: While some maintenance tasks can be handled by business owners, more complex issues should be addressed by professionals. If you notice persistent problems such as weak airflow, unusual noises, or frequent system cycling, it’s time to call an HVAC technician.

4. Upgrading Old Systems

Upgrading an outdated HVAC system can significantly improve efficiency and reliability. Newer systems are designed with advanced technology that enhances performance and reduces the likelihood of issues such as coil freezing.

How Modern Systems Are Designed to Prevent Common Freezing Issues:

  • Enhanced Refrigerant Management: Advanced systems better manage refrigerant flow to prevent low levels and leaks.

  • Improved Airflow Design: Modern units are designed to optimize airflow and reduce the risk of blockages.

  • Smart Thermostats and Controls: These allow for more precise temperature control and monitoring, helping to maintain optimal operating conditions.


Understanding the causes and prevention of HVAC coil freezing is crucial for maintaining a comfortable and efficient commercial environment. By recognizing issues such as insufficient airflow, low refrigerant levels, dirty coils, and other mechanical failures, you can take proactive steps to prevent these problems. Regular maintenance, proper installation, and timely upgrades are essential measures to ensure your HVAC system operates smoothly throughout the summer.

For expert advice and custom commercial HVAC coil replacement, contact Re-Coil Solutions. Our team of experienced coil technicians are ready to help you maintain the efficiency and reliability of your HVAC system. Reach out to us today to schedule a consultation and learn more about our high-quality HVAC products and services.


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