For peak efficiency, the cooling coil’s temperature should be higher than the dew point in the area where the unit is installed. If the temperature is lower, ice invariably builds up; it’s a simple enough problem. The refrigerant is not at fault. The unit does not need to be replaced. Maintenance is really the key to avoiding problems.
Here are some things to check when ice appears:
First is the A/C filter. This should be changed routinely or replaced every 2 weeks or sooner if there is cigarette smoke in the environment. Alternatively, the user can clean a filter by wetting it with water and then spreading a small amount of laundry soap over the surface. Let stand for several minutes and then cover with warm water and soak for at least 15 minutes. Rinse and dry.
Second is a dirty or blocked cooling coil. A/C needs professional maintenance every 2 to 3 years. As a DIY project, the owner should degrease and wash the build up of dirt, residue and debris as these hold on to pollutants in the air, adversely affecting heat transfer on the coil. The result can be a blocked coiling coil and weaker airflow.
Third is a dirty or blocked condenser coil which is located at the back of the unit. This part eliminates the heat that the unit is taking out of the area. Clean it every 2 to 3 years along with the cooling coil.
Dirt, allergens such as pollen and other pollutants build up on the inside surface of the condenser as air flows through the unit from inside to outside. If not attended to and airflow is impeded, the compressor run less efficiently. The resulting ice on the cooling coil may burn out the compressor. If necessary, call in a service technician to assist with taking the A/C unit apart and cleaning the condenser coil.
Fourth is an a compressor that is not pumping the refrigerant well, resulting in a cooling coil which is too warm to shut off the temperature (cold) control. Again, ice build-up occurs. Ice is the real culprit, not a defective compressor.
The fifth item to check when ice appears on an A/C coiling coil is the refrigerant gas. Too much coolant and too little coolant can cause ice to accumulate. Often, a unit has too much refrigerant just after it has been serviced. If it has not been serviced recently, than the above airflow issues are likely causing the ice.
Sixth, think about the temperature of the air outside the building. A crossover point seems to be 60 degrees F. A low outdoor temperature cools the coil. Room air temperature drops drastically, and ice begins to accumulate.
This situation happens a lot in the fall when outdoor temperatures may be quite high in the day but drop off drastically once the sun goes down. To remedy this, run just the fan on the air conditioner, and open the re-circulating vent. Doing this will move the room air and bring in some outside air through the night time hours. This air will not be cooled, however.
Seventh, the consumer must take care to purchase the proper sized unit for the space. If a unit is too large, the cooling cycles will be too short resulting in a unit starting and stopping and starting and stopping. The room will not receive proper cooling, and the unit will be working almost all the time, using too much energy. Consult a sizing chart for the correct A/C unit for the space.
Eighth, if the cold control on the air conditioner does not go off, the cooling coil will be colder than the dew point in the space. Ice will accumulate on the coil.
Lastly, a part called the cold control bulb could be broken or loose. As a result, the cold control on the unit does not go off, and the ice build-up starts. To check the cold control bulb, take the grille off the front of the air conditioner. Look at the bulb. If it is bent, loose or appears broken in any way, replace it, or point it out to a service technician.
As with any with any indoor environmental controls such as heat, air conditioning or just plan ventilation, routine inspection and maintenance goes a log way to efficient operation and warding off of long-term problems and unnecessary repairs. This is especially true of this simple accumulation of ice in A/C unit.