During the cold winter months, the efficiency of your heat pump might be compromised due to a common issue known as the freezing of the heat pump coils. Left unchecked, frozen coils severely reduce heating efficiency and can cause permanent damage.
The following sections cover simple prevention tips, signs of frozen coils, emergency defrosting steps, and when to call in an HVAC technician.
What is a Heat Pump Coil?
A heat pump coil is a crucial component in a heat pump HVAC (heating, ventilation, and air conditioning) system. Heat pumps compress refrigerant gas and expand to transfer thermal energy between indoor and outdoor coils.
Specifically, the outdoor coil on a heat pump acts as an evaporator in summer, absorbing ambient heat and passing it indoors, while a gas furnace relies solely on burning gas to heat air. During winter, the outdoor coil switches function as a condenser that releases concentrated heat extracted from inside to warm living spaces.
This outdoor coil contains thin aluminum fins and copper tubes filled with refrigerant. As hot gas or liquid passes through, heat gets exchanged to/from the coils out to external air for circulation. Proper airflow across these coils is vital for efficient operation.
Maintenance like brushing, cleaning, insulation, and preventing moisture buildup on the outdoor coil ensures maximum performance. If the coil gets too cold in winter, though, frost and ice can obstruct airflow, which is called a “frozen coil.” Special steps are required to defrost the coil and get the heat pump working again.
What Causes Frozen Coils?
Heat pump systems rely on a careful balance of refrigerant pressure, airflow volume, and defrosting mechanisms to prevent coil freezes.
When a heat pump fails to enter defrost mode at the right times, the likelihood of icing issues rises:
- Low Refrigerant Levels: Insufficient refrigerant gas due to leaks makes the system prone to freezing. Recharging is required.
- Dirty Filters and Coils: The buildup of dust, debris, and mold on filters and coils lowers airflow too much, leading to freezing.
- Extreme Cold Temps: Sustained sub-zero outdoor conditions overwhelm a heat pump’s defrost capabilities. Upgrades may be needed.
- Poor Airflow: Restrictions inside ductwork from crimping, closing vents, insulation blocking coil, etc., diminish airflow through the coil.
- Malfunctioning Defrost Sensors/Controls: Ice accumulates rapidly if automated defrost elements fail to cycle on periodically.
Frozen coil occurrences can be eliminated by correcting low refrigerant charges, cleaning coils/filters, ensuring adequate airflow, and repairing defrost controls. Call an HVAC company for troubleshooting help.
Signs of a Frozen Coil
Detecting early symptoms of a frozen heat pump coil allows you to address minor frost buildup before it causes permanent damage. Monitor your system carefully as the heating season ramps up.
Watch for these common indicators that your outdoor coil may have dangerous ice accumulation:
- Reduced Heating Output: Noticeably lower airflow and heat from vents signaling restricted performance.
- Ice Formation on Coils: Visible frost or ice around the edges of the coil and duct entry point.
- Increased Energy Bills: Significantly higher heating expenses as the system struggles under heavy load trying to maintain temperature.
- Fan Turning On/Off: Fan continually cycles on and off as freeze sensors get triggered. Listen for a rapid pulsing sound.
It’s best to catch symptoms early if possible, allowing quicker resolution before damage sets in. But do not hesitate to shut off your heat pump and call for service upon seeing actual ice accumulation on coils.
Defrosting a Frozen Coil
Finding your heat pump coil blocked with thick ice buildup can be alarming. But there are a few temporary steps you can safely take to melt the accumulating frost before calling for professional service. The key is promptly clearing the obstruction so your heating system can return to normal operation.
If your heat pump freezes up with substantial ice buildup, here are suggested defrosting methods:
- Turn Off System: As a first step, shut off the heating system to allow coils to defrost naturally once temperatures rise above 32°F.
- Use a Hair Dryer: Carefully aim a hair dryer or heat gun at iced areas to accelerate defrosting. Take precautions against condensate and electrical hazards.
- Check Drain Line: Clear coil drain pan and exit lines. Clogs stop condensate drainage, leading to re-freezing.
Ideally, full defrosting is completed within 30-60 minutes. Be patient and frequently check progress. DO NOT forcefully chip or scrape ice off the coils. Once fully defrosted, cautiously restart the heat pump and closely monitor system performance. Call a technician if the abnormal function continues.
Prevention Tips
Taking preventative measures is the best way to avoid frozen coil occurrences. You can minimize icing risks during winter by being proactive with regular maintenance and adjustments.
Follow these best practices:
- Keep Coils Clean: Regularly use a soft brush and coil cleaner to remove dirt and debris around coils. Change filters every 1-3 months as well. Dirty coils are more prone to freezing.
- Insulate Lines/Coils: Protect coils and connecting refrigerant lines from exposure using foam wraps or commercial covers. This safeguards against ice formation.
- Control Area Humidity: Prevent moisture with proper ventilation/air circulation in basements and crawlspaces around ductwork. Humidity contributes to frozen coils.
- Adjust Defrost Cycle: Most heat pumps have pre-set defrost timers. Adjust so it occurs more frequently in winter. Confirm proper functioning.
- Upgrade Heat Pump: Consider replacing an older unit with a new cold climate heat pump specifically engineered to prevent coil icing even in frigid temperatures.
Paying attention to coil cleanliness, insulation, moisture control, defrost settings, and equipment age/quality goes a long way in averting frozen coil events.
When to Call an HVAC Specialist
While limited frost can often melt harmlessly during manual defrosting, substantial ice buildup likely indicates professional assistance is required:
- If attempted defrosting does not resolve the frozen coil within 30-60 minutes, then underlying issues prevent heat pump operation. Continued running risks permanent damage.
- Visible ice forming on heat pump coils can break fins and cause refrigerant leaks over time. This requires special equipment to assess and repair.
- Handling refrigerants to recharge low levels requires certified HVAC training to mitigate risks. Do not attempt without proper credentials and gear.
- Identifying and correcting causes of heat pump freezing, like poor airflow or defrost sensor issues, needs specialized diagnostic equipment and expertise.
Don’t hesitate to call trained heating personnel if defrost attempts fail, you see ice accumulating, or general heating problems persist. Catching them early prevents costlier repairs later on.
The Logan Difference
Logan A/C and Heat Services has over 50 years of HVAC experience and expertise serving Ohio homeowners. Our technicians have seen it all when it comes to special situations like frozen heat pump coils and know exactly how to correct underlying issues.
We take pride in diagnosing problems accurately and completely—never resorting to temporary quick fixes. By adjusting refrigerant pressure, verifying defrost operation, inspecting ductwork, and taking all necessary steps, our team ensures frozen coil problems won’t return.
Of course, we perform expert installation and maintenance across all brands and models of HVAC systems as well. With access to premium equipment from leading manufacturers, we construct custom solutions tailored to your home and comfort needs.
Our friendly, responsive staff strives to educate each customer while treating you like family. We’re grateful to have built quality relationships across Dayton, Cincinnati, Columbus, and surrounding regions over the past 50+ years. Contact us anytime to experience the Logan difference yourself!
Frequently Asked Questions
What temperature causes heat pump coils to freeze?
Coils can begin freezing at temperatures below 45°F when compounded by moisture and restricted airflow. Sustained operation below 25°F almost always results in frost accumulation.
Is a frozen coil an emergency?
A lightly frosted coil may not require immediate shutdown. However, substantial ice buildup is an emergency, indicating mechanical issues needing prompt HVAC service. Take fast action to prevent permanent damage.
How often should I check my heat pump coils for frost buildup?
During winter months, visually inspect the outdoor unit coils at least weekly. Check more frequently during extreme cold snaps or heavy use. Catching minor frost early prevents major ice blockages requiring professional defrosting.
Why does my heat pump keep freezing up every winter?
Frequent winter coil freeze-ups likely point to low refrigerant charges, dirty filters/coils blocking airflow, poorly insulated ducts losing heat, malfunctioning defrost sensors, or general wear & tear. An HVAC technician should troubleshoot, identify the specific cause, and then implement the appropriate long-term solution.
How do I prevent ice dams on my heat pump?
Ice dams form when melting snow refreezes on the coil edges. Regular maintenance, like brushing coils clear of snow and re-directing gutter downspouts, prevents pooling water. Also, confirm the drain tube doesn’t get blocked. Stopping ice dams prevents major system disruptions.
What happens if you ignore a frozen coil?
Ignoring frozen coil symptoms risks complete heat pump failure and spending thousands on repairs/replacement. Refrigerant leaks, burnt compressors, and mold growth also potentially occur over time.
