This Air Conditioning project involved an attic-mounted central AC system with a heavily frozen evaporator coil. The pictures also show bent coil fins, an opened blower compartment, electrical controls, refrigerant tubing, and duct connections covered with gray sealing material.
A frozen coil may look like the Air Conditioner is producing extra cold air. The opposite is usually true. Ice blocks air from moving through the coil. As the ice gets thicker, the home may receive less Cooling even though the system continues running.
The repair process focused on finding out why the coil froze, checking the indoor HVAC equipment, inspecting airflow, protecting the system from water damage, and sealing areas where conditioned air could escape into the attic.
Opening and Inspecting the Attic Air Handler
The first picture shows the inside of the air handler. An air handler is the indoor part of a central Air Conditioning system. It contains the blower, electrical controls, wiring, and other parts that help move cooled air through the home.
Power should be turned off before removing these panels. The technician can then inspect the control board, wire connections, transformer, blower motor, and blower wheel. The blower wheel is the round fan that pushes air across the cold coil and into the duct system.
A weak blower motor, dirty blower wheel, loose wire, damaged control board, or incorrect fan speed can reduce airflow. When too little warm air moves across the evaporator coil, the coil can become cold enough for moisture to freeze on its surface.
Checking and Sealing the Duct Connections
Several pictures show the metal supply box and duct connections in the attic. The seams have been covered with HVAC mastic. Mastic is a thick sealing paste made for air ducts. It dries into a strong layer that helps stop air from leaking through gaps and joints.
Attics in Las Vegas and Clark County can become extremely hot. A leaking supply connection can allow cooled air to escape before it reaches the rooms. A leaking return connection may pull hot, dusty attic air into the system.
Sealing these seams helps the Heating and Cooling system move more of its air into the home. It may also improve room comfort, reduce dust entering the ductwork, and lower the amount of time the central AC must run.
Homeowners can learn more about complete system service on the Fast Affordable Air HVAC Services page.
Finding the Frozen Evaporator Coil
The evaporator coil is the indoor coil that removes heat from the air. Refrigerant flows through small tubes inside the coil. Warm household air passes across the thin metal fins, gives up its heat, and returns to the rooms as cooler air.
The close-up pictures show frost spread across a large part of the coil. This is called a coil freeze-up. The ice fills the small spaces between the fins and blocks airflow. Running the Cooling system in this condition can place extra strain on the blower and compressor.
Possible Reasons the Coil Froze
A frozen evaporator coil is a symptom. It does not tell us the exact cause by itself. The technician must inspect the full system before deciding what needs to be repaired.
- A dirty or overly restrictive air filter
- Closed or blocked supply vents
- A dirty blower wheel
- A weak or failing blower motor
- An incorrect blower speed
- Dirt packed between the evaporator-coil fins
- Low refrigerant caused by a leak
- A restriction in the refrigerant system
- A thermostat or control problem
Refrigerant is the fluid that carries heat through the Air Conditioner. It is not normally used up like gasoline. If the refrigerant level is low, the system should be inspected for a leak instead of simply being refilled without further testing.
Allowing the Ice to Melt Safely
The compressor should not continue running while the evaporator coil is frozen. The Cooling mode is turned off so the ice can melt naturally. The indoor fan may be operated when it is safe and working correctly because room-temperature air can help the coil thaw.
Sharp tools should never be used to chip ice away. The coil contains delicate tubing that can be punctured. Even a small hole can release refrigerant and turn a simpler airflow repair into a much larger coil repair.
As the ice melts, a large amount of water may enter the drain pan. The technician should inspect the condensate drain, secondary pan, and safety switch. Condensate is the water removed from humid indoor air during normal AC operation.
Inspecting the Damaged Coil Fins
One picture shows an area where the thin aluminum fins are crushed and folded over. These fins give the coil a large surface area so it can collect heat from the passing air.
Bent fins can block part of the airflow. Minor damage may sometimes be corrected with a fin comb. A fin comb is a small tool that helps straighten the metal rows without cutting the refrigerant tubes. Severe damage, corrosion, or a refrigerant leak may require a larger repair or coil replacement.
Once the ice has melted, the coil can be inspected for dirt, oily marks, corrosion, and damaged tubing. Oily residue can sometimes be a sign of a refrigerant leak, but proper leak-detection equipment is needed before confirming one.
Cleaning the Coil and Correcting Airflow
If the coil is dirty, it can be cleaned with an evaporator-coil cleaner that is safe for the equipment. Dirt must be removed without flattening more fins or pushing debris deeper into the coil.
The filter, return-air path, supply vents, blower wheel, blower motor, and fan-speed setting should also be checked. Correct airflow allows warm air from the home to move evenly across the full coil.
Regular cleaning and airflow checks are part of proper AC maintenance in Las Vegas. More information about seasonal inspections is available on the Air Conditioning tune-up page.
Testing the Central Cooling System
Refrigerant testing should be completed only after the coil has fully thawed and airflow has been corrected. Ice can cause inaccurate pressure and temperature readings.
The technician can then check refrigerant pressures, superheat, subcooling, motor amperage, drain operation, and the temperature difference between the return and supply air.
Superheat and subcooling are temperature measurements used to show how refrigerant is moving through the system. They help determine whether the system has the correct refrigerant charge or another problem that affects Cooling.
The blower and compressor should be observed through a complete cooling cycle. The technician also checks that the coil remains free of frost and that water flows safely through the condensate drain.
Details about common repair services are available on the Fast Affordable Air AC Repair page.
Benefits of Repairing the Frozen Coil and Duct Leaks
- Stronger airflow from the supply vents
- Better heat removal from the indoor air
- More even temperatures throughout the home
- Less strain on the blower motor and compressor
- Reduced loss of cooled air inside the attic
- Lower risk of water overflowing from melting ice
- Less unnecessary energy use caused by long AC run times
- Improved reliability during hot Las Vegas weather
