This is our first summer in a new house which has central air. It was a bit hotter today than normal so the AC was running for a long time. After awhile we noticed the airflow stopped because the cooling coil completely iced over (about 1/4" of snow over the whole thing). Bits of the suction line, including where the suction lines meets the outside unit, where also iced over. We opened up a couple registers which we had closed for the winter, and fixed a blockage of our largest return vent. The system seems to be working better now, its been on for hours and is still working. However I have noticed that the bottom inch of so of the A shaped coil is frosted over as are most of the loops on the sides. Is it alright to have some frosting of the cooling coil or should it be completely clear at all times? The suction line (the larger pipe) should never be iced up during normal operation. By the time the refrigerant gets to the end of the evaporator coil, it should be completely boiled off (in a gas state).

The bottom few coils may frost up, but the top ones should only be sweating at most. If the suction line; or more than the bottom third of the coil, is frosted up. You either have an overcharged system, or you're not getting enough air flow over the coils. Make sure all registers and returns are open, and unobstructed. Check all filters, to make sure they're clean. If you have a multi-speed blower, make sure it's set to run at the proper speed. And make sure it's actually running at, or near the speed it's supposed to be running at. If none of that helps, have an HVAC technician check the refrigerant level. Temperature and pressure are the same thing in a refrigeration system, so based on the pressures shown above you can easily determine the temperature of the refrigerant . Assuming this is an R22 system, you'll see that the refrigerant enters the evaporator at 26°F, and leaves above freezing at 43°F. The suction line in this system is above freezing, so no icing will take place.

The temperature may be below the dew point, so there may be sweating (condensation).install window unit air conditioner Not enough air flowcentral air conditioner repair service In this example you can see that the refrigerant enters the evaporator at 26°F, but it leaves the evaporator below freezing at 31°F. room air conditioner portable unitSince the suction line in this case is below freezing, there may be frosting/icing of the line. If the temperature of the line stays below freezing all the way back to the compressor, you'll see icing all the way along the line. In this case, there's not enough air flowing through the evaporator. Because of this, not enough heat is being transferred to the refrigerant.

Sorry, I don't have an image for this. In this situation, you'll see that the temperature of the refrigerant entering the evaporator is so low. That even with good air flow, enough heat cannot be transferred to bring the refrigerant above freezing. While icing due to low refrigerant is rare, and often requires other problems, it can happen. Because the pressure in the evaporator is so low, the boiling point of the refrigerant is well below 32°F. This causes the coils closest to the metering device to be very cold, which causes moisture to freeze. As the coil freezes, air flow is restricted. As air flow is restricted, less heat is removed from the refrigerant. The freezing slowly creeps through the coil, and eventually makes its way back along the suction line to the compressor.Browse other questions tagged hvac air-conditioning ice or ask your own question.Step 1: Cutting out the partsShow All ItemsWritten There may be Two reasons for the water leakage and ice buildup.Blocked water drain pipe.

Refrigerant LeakageDirty FiltersBlocked water drain pipe.Actually there is no water in the split Ac system. The water is produced in the internal unit because the cooling of air causes the water present in the air to condense into small water droplets (similar to water condensing on a cold bottle)This water is then drained out through the drain pipe, which in a split ac is dusted out along with the power wires and the copper tubing.Thus if the drainage system is faulty or blocked, water collects in the inner unit and starts flowing and leaking out from the inner unit.Drainage problem: When hot, humid air hits the evaporator coil, it removes heat and moisture from the air before circulating it back into your home. Especially in humid climates, the A/C condenses a lot of vapor into condensation that should drain outside. However, if water builds up in the condensate drain and starts to get backed up, the coil freezes the condensation and the ice further blocks the drain, exacerbating the situation further.

Source: What Causes an Air Conditioner to Ice UpRefrigerant LeakageThe Gas is leaking in your AC. So the lower pressure of refrigerant is causing evaporator coils in inner unit to Ice up, When some of the ice falls on the fan it is thrown out from the indoor unit.When AC has Low refrigerantWhen the refrigerant in the system is low, the pressure; and therefore temperature, of the refrigerant will also be lower. In a normal system, the temperature of the refrigerant at the beginning of the evaporator will be right around the freezing temperature of water (32°F). As the indoor air moves over the cool coils, the moisture in the air will condense on the coils. This condensation will drip harmlessly off the coils, and into the condensate drain.When the refrigerant is low, the temperature of the refrigerant at the beginning of the evaporator coils will be colder than the freezing point of water (less than 32°F). Because the coils are so cold, the condensation that forms on the coils will freeze.

As ice builds up on the coils, it restricts the air flow through the coils. Because of the restriction, the refrigerant can't absorb as much heat from the the indoor air moving over the coils. This causes the refrigerant to boil later in the evaporator, which causes ice to form further along the coils. This situation continues to progress, until the whole evaporator is a block of ice. Once that happens, the refrigerant will start to boil in the suction line. This cause the temperature of the suction line to drop, and just like in the evaporator, cause the condensation to freeze.Eventually the freezing works its way all the way back to the compressor, which is where the trouble can really start. If allowed to operate in this condition for too long, liquid refrigerant can make its way back to the compressor. If this happens, the compressor can be damaged.It should also be noted. Once the refrigerant level drops too low, the system stops working. So this problem only occurs in a "sweet spot", where the refrigerant is low, but not too low.

Source: Why do the evaporator and suction lines freeze when there is low refrigerant?Dirty filtersDirty filters hinder airflow and can cause icing up of the Evaporator coils. Please clean filters in your AC and see if it solves the problemThe warm air from your home needs to flow through the system fast enough that it keeps the coil above freezing. If there isn’t enough airflow, the coil becomes too cold and freezes condensed water before it drains away. One major cause of inadequate airflow is a dirty filter. Change the filter to improve airflow.Source: What Causes an Air Conditioner to Ice UpPlease get the AC serviced by a professional ASAP.Please ask the AC repair professional to trace the source of Leakage (if any) before filling or topping up the refrigerant.Please stop running the AC till servicing is doneStay Cool… Written Written Ductless air conditioning depends on refrigerant to do its job, just like centralized systems do. It needs to be present in a specific amount in each unit, and it can’t leak or otherwise lose refrigerant.