Causes of frostbite of the outdoor unit air conditioner tube

The following parts of the outdoor unit can freeze:

Both the thick and thin tubes. Sometimes the outdoor unit itself also freezes.
If you see frost on any elements of the outdoor unit, do not hurry to be upset: in some cases, it is a normal situation:

When frost penetration of tubes of an outer block of conditioner is not the breakage

First switching on of air conditioner after winter. Tubes often freeze at the first start-up of the split system after a long idle time. Give a chance to work an hour or two on the air conditioner. Probably the tubes will thaw and will not freeze anymore.

A light layer of frost on the pipes. It is possible if the split system works correctly on all modes and there is no “furring” in the external unit. A small layer of frost turns into the weak condensate on the tubes during the “vacation” of the conditioner.

If you see a lot of ice in the outer unit, or the presence of frost on the tubes is combined with poor cooling of the air conditioner – most likely, we are talking about a breakdown.

Reasons why a thick air conditioner tube is freezing

The appearance of frost on the thick tube of the external air conditioner unit and its nut is due to the fact that the cooling process continues after the internal unit. This happens because the refrigerant does not completely boil off in the evaporator. The “boil off” occurs in the compressor suction tube, which causes it to freeze.

Quite often the reason is not in the breakage, but in a wrong installation, incorrect service, or unprofessional repair of the conditioner. Some of the most common installation, maintenance, and repair mistakes that cause a gas tube to freeze include:

Excess refrigerant. If too much Freon was poured into the split system during installation or topping up, it will boil not only in the evaporator but also in the thick tube.
Short trace. Each manufacturer of air conditioners prescribes in the instruction the allowable length of the route. If it was shortened during installation, this will also cause the low-pressure tube to freeze.

A thick tube is broken. Sometimes in the “homemade” installation of air conditioners, the tube is bent. This leads to disruption of freon circulation, as a consequence, it partially boils in the gas tube, and you see ice on it.

If the conditioner was working normally before, it was not recharged, and frost is beginning to appear on the thick tube – the breakage has happened. Here is a table, which will help you to determine by yourself exactly what is malfunctioning in your split system, and will help you to estimate the order of repair expenses.

Dirty inside unit of split-system
Because of the accumulated dust and dirt, the heat exchange decreases, which leads to the malfunction of the conditioner.

Dirt on the outdoor unit
Large amounts of dirt and dust reduce the heat transfer from the outdoor unit to the environment and cause the split system to malfunction.

Failure of the indoor unit fan
The air conditioner blows poorly and cools weakly. At the same time on the outdoor unit, the suction pipe is covered with a thick layer of frost.

Reasons why the air conditioner’s thin tube is freezing

Moisture in the cooling circuit. This could happen if unprofessional repairs were done to fix a leak or refill the air conditioner with refrigerant.

The route is too long. Longer than it is provided by the manufacturer of split-system.

Partial overlapping of the faucet valve on the thin tube. This causes it to boil before the evaporator and the liquid tube freeze.

If the conditioner was not touched before it worked properly, and the high-pressure pipe is freezing – most likely, some breakage has happened. The most common are the following.

Capillary tube clogging
Due to clogging of the capillary, there is a large pressure drop at the inlet and outlet of the capillary. It leads to early boiling of freon and cooling, even before the refrigerant enters the evaporator.

Lack of refrigerant
Freon leakage can occur both because of depressurization of the circuit, and as a result of the long-term operation (annually conditioners can volatilize up to 7% of the refrigerant).

Reasons why both tubes on the outdoor unit of the air conditioner freeze

If your air conditioner is running on “heat,” then the frosting of the outdoor unit tubes is normal. On the “rest” cycle, the tubes will thaw. Then the frosting mode will repeat.

The only thing one should remember – is you can use a conditioner both for heating and for cooling only when the temperature outside is not lower than the supposed for your model. Ignoring this rule very often leads to the freezing of both tubes, nuts, and the whole outside unit. In particular, this happens when:

Operation of the air conditioner on cooling when the outside temperature is low.
Operation of the air conditioner on “warm” when the outside temperature is low.

Note: The temperature ranges of the split system depend on the brand and the unit. For example, inverter models can be operated at lower temperatures (down to -10 to -15°C) than conventional models. To know the permissible outdoor temperature limits for your air conditioner, please refer to the operation manual or the technical data sheet of the equipment. Note that for cooling and heating modes, these ranges will be different for the same air conditioner.

Please note! If the all-the-year-round operation of a split-system is necessary, conditioners are equipped with a “winter set”. It consists of a sensor, which decreases the rotational speed of the outside fan at low temperatures (this decreases the formation of frost in the outside block), and also systems of heating for the compressor and draining. Together, they help prevent oil from thickening, and they also heat the drainage system. With the winter kit, the split system can be used up to -25 -30°C outside. You can order a winter kit installation at our SDAC Heating & Air Conditioning service center.

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