When your air conditioner freezes up, it can be a major inconvenience. Ice formation stops the unit from cooling effectively.
We offer expert advice that's easy to follow, including when to thaw your AC, how to fix the issue, common causes, and preventive measures to avoid future problems.
First, Should I Call a Technician When My AC Freezes?
If you are certain that the air filter is dirty and you forgot to replace it, then do not call a technician. Thaw out the ice on the AC, replace the air filter, and you should be good to go. If freezing happens again, then call a technician.
How to Thaw a Frozen AC Unit?
A better question is: should you thaw a frozen AC? The answer is a mixed bag. Thawing a frozen AC unit requires careful consideration, and whether you should do so depends on the underlying cause of the freeze. Here's a breakdown:
Yes, You Should Thaw: If you're certain that a dirty air filter is the reason behind the frozen AC, then thawing is recommended. A dirty filter restricts airflow, leading to ice buildup on the evaporator coil.
No, You Shouldn't Thaw: If you're uncertain about the cause of the frozen AC, it's best not to thaw it yourself. Thawing may exacerbate the issue if the cause is different from a dirty filter.
Steps to Thaw Your Frozen AC
- Turn Off the System: Switch off the AC from the breaker to allow the ice to melt naturally.
- Monitor Drainage: Ensure water drainage doesn't overflow, especially for attic AC units.
Practices to Avoid
Switching Thermostat to Heating Mode or Fan Only Mode: Some HVAC companies suggest switching the thermostat to heating mode or keeping the system on blower fan mode only. We do not recommend these practices, as they can potentially:
- Damage the blower fan motor
- Lead to water overflow, causing costly mold growth
The following picture shows condensation water frozen in the drain line. If the ice melts, it has nowhere to go other than overflowing on the side and ruining the attic.
Instead, it's best to seek assistance from a reputable local HVAC company. They can provide expert advice and assistance, utilizing the pattern of the frozen air conditioner to diagnose and resolve the issue effectively. Don't hesitate to reach out to professionals for help to avoid further damage and ensure the proper functioning of your AC system.
Frozen Evap Coil Flow Pattern
The frozen ice pattern would will be extremely helpful for technicians but a more through investigation is necessary. Following are some suggestive hints:
Low Charge Ice Pattern
Notice partial freezing ice pattern at the begining of the evaporator. This could be due to Low Refrigerant Charge or Restriction in the filter dryer.
Dirty Filter Ice Pattern
Typically when the whole evaporator is frozen solid it most likely airflow problem. This could be caused by either dirty air filter, or Fan Blower.
Exhaustive Compilation of Causes of Frozen Air Conditioner:
After years of experiencing numerous frozen air conditioners in the field, air conditioner freezing can be attributed to three main categories:
| Cause | Frequency |
|---|---|
| Airflow Problems | Around 50% of cases |
| Low Refrigerant Charge | Around 40% of cases |
| Restricted Refrigerant Lines | Around 10% of cases |
Let's examine each category in detail:
Air Flow Problems:
- Dirty Air Filter: A dirty air filter be it MERV or Not restricts airflow, causing the evaporator coil to become colder than normal.
- Dirty Evaporator Coil: Accumulated dirt and debris on the evaporator coil can impede heat transfer and lead to freezing.
- Bad Thermostat: A malfunctioning thermostat may fail to energize the blower, resulting in insufficient air circulation.
- Blower Motor Issues: Problems like loose connections, faulty control boards, or failed motor capacitors can hamper the blower's operation.
- Closed or Blocked Vents: Too many closed supply vents, balance dampers, or malfunctioning zone dampers can restrict airflow, leading to freezing.
Low Refrigerant Charge leading to Air Conditioner Freezing Up:
- Insufficient refrigerant charge reduces the pressure and temperature in the evaporator coil, causing it to freeze. It happens during the first installation or is caused by a refrigerant leak.
Restricted Refrigerant:
- Malfunctioning TXV: A faulty thermostatic expansion valve (TXV) can cause improper refrigerant flow and result in freezing.
- Clogged Piston: A clogged piston in the metering device restricts refrigerant flow and contributes to freezing.
- Clogged Strainer or Filter Drier: Accumulated debris as shown in this Danfoss Case study the strainer or filter drier can impede refrigerant flow and lead to freezing.
Understand the fundamentals of a frozen AC
Don't overlook the intricacies of a well-functioning refrigeration system. It operates through a delicate balance of sequential actions, and any deviation or shortcut can result in frozen AC coils, inadequate cooling, compressor failure, and irreparable damage to your air conditioner. The factors contributing to an AC freezing up can be categorized into three main areas: a) Insufficient Air Flow, b) Restricted Refrigerant Pathways, and c) Low Refrigerant Charge. In our comprehensive discussion, we delve into these issues, provide detailed insights, and offer recommended solutions for each
Adequate airflow is the lifeline of your air conditioner. Ignoring airflow problems is like suffocating your AC and inviting frost to take over. - ZD
Blocked Airflow Freezes Your AC
Insufficient airflow to the evaporator is a common issue that often causes air conditioners to freeze up.One frequently underestimated component crucial for proper AC function is the air filter. A dirty air filter, especially one with a low MERV rating, can significantly block airflow to the evaporator, reducing heat exchange as explained by the US Department of Energy. When the filter is removed or replaced with a low-efficiency one, dirt particles can build up in the evaporator coil or blower or both. While replacing the air filter is a cost-effective do-it-yourself task, cleaning the evaporator coil requires meticulous attention and the expertise of an experienced HVAC professional.
Many homeowners underestimate the importance of air filter size in their HVAC systems. Industry standards often prioritize affordability during installation, leading to undersized filters. The recommended minimum is 1 square foot of filter per 1 Ton (around 12,000 BTU) of cooling capacity.
However, for optimal performance and long-term savings, we highly recommend oversizing the air filter on the return duct to 1.5 or 2 or more square feet per ton. While there may be a slightly higher upfront cost, the benefits outweigh the initial investment.
By opting for larger air filters, you increase the surface area available for filtration, thus reducing the pressure drop. This allows the filters to capture more dust, debris, and allergens, leading to better indoor air quality and improved system performance. Additionally, larger filters typically need to be replaced less frequently, reducing maintenance costs over time.
Investing in properly sized air filters can ultimately result in improved energy efficiency, reduced wear and tear on your HVAC system, and lower long-term operating costs. It's a smart investment that pays off in terms of both comfort and savings.
Close-up of a dirty Air Filter
A dirty air filter is one of the primary culprits behind frost formation in an Air Conditioning system. Including air filter maintenance in your preventive maintenance program is essential. While replacing an air filter is a task that can be done by yourself, it's important NOT to settle for cheap options. Instead, opt for a high-quality and durable air filter to ensure optimal performance and prevent ice build in your AC system.
Dislodged Air Filter
When low-quality filters are forced out of their track and obstruct the blower's airflow, insufficient airflow occurs. This impairs heat exchange, leading to ice formation on lines or coils. Promptly securing filters and ensuring uninterrupted airflow prevents frozen coils or lines, protecting your air conditioner's performance.
Loose Insulation Material
Diagnosing loose insulation material in an HVAC system can be challenging as it is not easily visible from the outside. This issue typically occurs when the system is running. As the blower operates, it can suck loose insulation material towards the blower or the evaporator coil, resulting in restricted airflow and caused the compressor to fail. Properly diagnosing this problem requires the expertise of an experienced HVAC technician who can accurately identify and address the issue.
While air filter-related issues are among the most frequent causes of an icy air conditioner, a malfunctioning or broken Fan Blower could also be a cause as it is the main mechanical part generating the required airflow. Malfunctioning of a blower fan motor could be either electrical such as a bad capacitor or a broken relay or straight-out mechanical such as a broken shaft or jammed bearing.
For safety reasons, using lock out tag, only qualified HVAC should inspect Blower motors, some DIY homeowners inspect blowers with the thermostat OFF while the safety disconnect switch is ON - this is a major safety hazard as the thermostat could be switched to ON while someone's hand is inside the blower.
Dirty Evaporator Coils or Dirty Blower causes air conditioner freeze up
This has been a documented fact and often misunderstood. By opting for lower quality air filters or removing air filters all together will have devestating consequences. Shown next are perfect examples.
Dirty Fan Blower
In the absence of good quality air filters, the fan will be exposed to all sorts of contaminants. Ultimately, dirt, hair, lint, dust end up in the blades of the blower fan, reducing air flow and cause frozen ACs.
Dirty Evaporator Coil
In the absence of good quality air filters, Dirt, hair, lint, dust end up at the fins of the evaporator coils not only provide a perfect environment for mold growth but also reduce air flow and causes frozen ACs.
Low Refrigerant Charge will cause Frozen Air Conditioner
Ice buildup on air-conditioning units is often caused by low refrigerant levels, which ranks as the second most common factor. Air contains water molecules known as humidity. Under the correct temperatures, the water molecules condense into liquid and further solidify into ice near 32F. When the unit operates with insufficient refrigerant, the evaporator freon pressure decreases and the temperature of the evaporator coil drops below 32°F, the freezing point of moisture in the air.
This temperature drop causes the moisture in the surrounding area to freeze onto the coil's surface. Initially, it forms a thin layer of frost, but over time, it can accumulate and transform into a thick sheet of ice.
In an air conditioning system, Freon operates as a closed-loop system, meaning the refrigerant should not escape. Low refrigerant levels typically indicate a refrigerant leak somewhere within the system, whether in the lineset or in components like the condenser or evaporator coil that regularly handle refrigerant.
Handling tasks such as charging an AC system with Freon, locating and repairing refrigerant leaks, and checking refrigerant levels should be left to the experts. Considering the mis-use of R22-Phaseout by the EPA, these activities require EPA-certified HVAC professionals who understand the complexities handling of these substances while keeping the environment safe.
AC Restrictions: Why Trust an EPA-Certified Technician?
Discover the complexities of AC restrictions and why it's crucial to rely on an EPA-Certified technician for expert solutions. In a closed-loop refrigerant system, restrictions are rare due to AC-designed efficiency. However, when restrictions do occur, they can cause your air conditioner to freeze up. Even a properly charged system can suffer from restricted pathways, resulting in insufficient refrigerant reaching the evaporator. Diagnosing and repairing these restrictions is a challenging task, categorized as a significant job that involves handling freon. It's essential to seek assistance from a reputable HVAC company for a second opinion, as restrictions are often misdiagnosed by inexperienced technicians. But how can restrictions occur in a closed system? Impurities, such as gasket debris blocking an orifice or a malfunctioning mechanical spring in the TXV, can lead to restrictions. Additionally, clogged filter dryers or decomposed beads migrating through the closed loop can contribute to the problem. Trust our EPA-Certified technicians to tackle AC restrictions and restore optimal performance to your system
Easy Solutions to Fix a Frozen Air Conditioner:
If your air conditioner has frozen up, here are some steps you can take to resolve the issue:
- Turn off the AC: Switch off the air conditioner to allow the ice to melt and prevent further damage.
- Check and Replace the Air Filter: If the filter is dirty, replace it with a clean one to improve airflow.
- Thaw the Coil: Use a gentle heat source, such as a hairdryer on low heat, to carefully thaw the frozen coil.
- Check for Airflow Restrictions: Ensure that vents are open, dampers are properly adjusted, and there are no obstructions blocking return air.
- Inspect and Clean the Evaporator Coil: If the coil is dirty, clean it using a soft brush or contact a professional technician for thorough cleaning.
- Verify Refrigerant Levels: Consult an HVAC professional to check and replenish refrigerant if necessary.
- Address Any Identified Component Issues: If blower motor, capacitor, or control board problems are detected, consult a professional for repairs or replacements.
Prevention Measures:
To prevent future instances of air conditioner freezing up, consider the following measures:
- Regular Maintenance: Schedule routine maintenance and inspections to keep your air conditioner in optimal condition.
- Clean Air Filters: Regularly replace air filters to ensure proper airflow.
- Keep Coils Clean: Maintain cleanliness of the evaporator and condenser coils to promote efficient heat transfer.
- Professional Tune-ups: Enlist the services of a qualified HVAC technician for regular tune-ups and system checks.
- Address Any Airflow Issues: Ensure adequate return airflow and keep supply vents unobstructed.
By addressing these causes, implementing solutions, and following preventive measures, you can reduce the chances of your air conditioner freezing up and enjoy consistent cooling performance.
Conclusion:
Air conditioner freezing up can be caused by various factors related to airflow, restricted refrigerant, and low refrigerant charge. Insufficient airflow due to a dirty air filter is a common issue that can contribute to freezing. Regular maintenance, including cleaning or replacing air filters, is crucial to ensure proper airflow and prevent the accumulation of dirt in the evaporator coil. Low refrigerant charge and AC restrictions are complex issues that require the expertise of EPA-certified HVAC professionals to diagnose and address properly. By addressing these causes, implementing solutions, and following preventive measures, you can avoid inconvenient freezing issues and enjoy uninterrupted cool comfort all summer long.
Remember, if you encounter persistent issues or are unsure how to repair a frozen air conditioner, it's always advisable to seek assistance from a qualified HVAC professional. They have the knowledge and experience to accurately diagnose and resolve air conditioner freezing issues, ensuring the longevity and efficient operation of your cooling system. Stay proactive in caring for your system, and enjoy uninterrupted cool comfort all summer long.
Bonus Note: With 17 years of experience designing air filters for the world leader, our indoor air quality and air filter expertise are simply among the best. We understand the critical role air filters play in maintaining proper airflow and preventing issues like air conditioner freezing. When choosing an air filter, pay attention to the MERV (Minimum Efficiency Reporting Value) rating, which is determined by ASHRAE Standard 52.2, the recognized committee for air filter testing protocol. A good residential filter should have a minimum MERV 8 rating and feature a reliable backing material for structural integrity. Avoid low-cost, throw-away filters without backing, as they collapse and cause air conditioner freeze up.
Now, you may wonder if it is possible to install a MERV 13 filter in a residential system as recommended by ASHRAE. The answer is YES, it is feasible after making modifications to the filter handling frame and conducting an airflow check. However, it is important to consult with a knowledgeable HVAC professional who can assess your specific system's compatibility and make the necessary adjustments to ensure optimal performance and airflow.