In a recent blog post, we spoke of the importance of an AC filter change. Today we are taking things a step further and discussing why does an air conditioner freeze?
One of the most common reasons your air conditioner to freezes up is due to a clogged filter. An ac unit needs adequate airflow to keep critical parts warm. Other reasons include low refrigerant, fan operation, or unexpected rain. An air conditioner should ideally provide cool air at 55 to 60 °F.
Below we dive deeper into the reason why an air conditioner freezes:
Low Air Flow
The cooling from your air conditioner is supposed to go into the air that passes over the coil. If there is not enough air, the coil becomes very cold and freezing temperatures occur. The ice blocks the airflow even more, and ice forms rapidly on the coil. Once the system starts to freeze, it won’t be long before the coil is completely blocked with ice and no cooling goes to the home.
Low airflow occurs because of dirt clogging the blower or coil, grilles that are blocked or closed or the mechanical failure of a blower component. We recommend membership in Comfort Club to ensure system cleanliness and reliability of all component parts.
Most of us have experienced an air conditioner that will not cool because it is low on refrigerant. It is difficult to understand how an air conditioner can freeze up for that same reason.
It has to do with the science of pressure and temperature. Perhaps you have experienced it takes longer to boil an egg in the mountains than it does here in Jupiter, Florida. Water boils at a lower temperature at a higher altitude and corresponding low atmospheric pressure. In Denver, Colorado water boils at 203 oF. (95 oC) as opposed to 212 oF (100 oC) at sea level. Similarly, a cooling coil that is designed to operate at 40 oF reaches the freezing point when it is low on refrigerant. Again, we recommend membership in the Comfort Club to help avoid a costly air conditioner repair.
Air conditioners are made to operate in all kinds of weather. Your AC unit operates more efficiently when outdoor temperatures fall, and heavy rains follow. But rain also contributes to many air conditioner freeze-ups. If airflow is already restricted or refrigerant charge is low (or both) a heavy rain will almost certainly trigger a freeze-up.
This is because water mist and droplets drawn into the outdoor unit carry away heat nearly 25x as fast as does air. The moisture in the air ‘superchargers’ your air conditioner’s performance. The air coming out of the grilles may become 5 or 10 degrees cooler during heavy rain.
It is not unusual after a thunderstorm that we hear of one or two air conditioners freezing up. Most often, the owner thought everything was OK except perhaps on the warmest days when the unit ‘did not quite keep up’. A rain shower revealed the problem that was there all the time. They could have avoided the inconvenience of a costly service call if they had a Comfort Club membership to deal with these conditions before they became a problem.
Why are Freeze-Ups a Problem?
In most cases, we cannot make an effective diagnosis until the ice has melted. Your cooling must be turned off for as long as several hours to ‘defrost’ (NEVER USE A TOOL TO REMOVE ICE – a slip of a screwdriver can do hundreds of dollars in damage). Ice also blocks many of the tiny passages used to drain water from the AC unit. Ice formation can lead to damaged insulation, ceilings, ducts, and flooring.
Remember how ice cracks water lines, sidewalks, roads, and brick walls in northern climates? Ice can crack the cooling coil or cause fittings to separate. In extreme cases, it can damage your compressor. Coils and compressors are the costliest AC components. Failure often means the system should be replaced.
Why Become a Comfort Club member?
Airflow, refrigerant, and borderline conditions are each checked at the time of your twice-annual Comfort Club service.
At Complete Comfort, we emphasize the power of a strong preventive maintenance discipline that proves its value time and time again. When you do your regular AC filter change and call on Complete Comfort for regular service, you have done everything you can to ensure your AC will run efficiently and reliably.