Air Conditioning Problems

Determine the cause is the first step. An air conditioning system normally runs 40-45 degrees Fahrenheit or 4-7 degrees Celsius so if the refrigerant charge is low, or once the refrigerant feed to the evaporator is reduce or the air flow is reduced or lessen then freezing will occur. It will cause the evaporator temperature will drop if any of these parameters or any combination of them. If evaporator reaches 32 degrees Fahrenheit or 0 degrees Celsius the freezing will begin to wherein the ice forms on the coil, the air flow will lessen and accelerates the freeze.

Common causes are:

Low Ambient - when the outdoor temperature is too low, below 65 degrees Fahrenheit. Once the Air conditioning runs in the low temperature it will cause the evaporator coil to drop in temperature and freeze over. To prevent this you need to use a low ambient control to shutoff the air conditioning when it’s too cool outside, and to slow the condenser fan use a speed control.
It causes some serious problems when your unit freeze’s over. The water drips down the return air ductwork and collects, when a unit is in a roof top, it will provide a place for mold and bacteria to grow or will directly drip  on the ceiling that cause damage to tile or electrical system. The freezing may also cause liquid refrigerant to return to the compressor, it will damage the piston, valves and crankshaft, which is too expensive to fix.

Lack of airflow is the most frequent cause of freezing. Dirty air filters were formed that clog the airflow to the evaporator, many supply air dampers was closed. Under sized or poorly designed ductwork, dirty evaporator coil, too much dirt built-up on the fan blades, broken fan belt or if a fan motor failed is other cause.

The evaporator coil can also freeze from a lack of a refrigerant, it will happen only if refrigerant is slowly leaking and the cooling will stop completely. If this happened leak is en need to be located or repaired.

Once you determined the cause it is need to a proper repair, some of the mechanics are trying to resolve coil freezing by jamming more refrigerants into the system.

It is very expensive to repair the cause of the freezing like undersized ductwork; extensive renovation is necessary to replace the ductwork, so in this case, a freeze stat can be add to the system to shutdown the compressor when the freezing occurs. Freeze stat is a little snapdisc switch that will clip to the end tubing to the evaporator and when the evaporator falls to 34 degrees Fahrenheit to 1 degrees Celsius it will open. It will prevent the coil from forming ice and damaging your equipment.