Refrigeration filter driers: what are they and what are they for? The dried filter, also called accumulated filter, is a component that is made to locate the condenser and the valve in the high pressure area of the air conditioning circuit. The purpose of the filter is to remove debris and sand from the flow of the circuit, as well as absorb any moisture and dirt that circulates throughout the system Oil and coolant, important liquids for the stability of the entire apparatus, are also stored there. Similar filtration technology exists in the accumulator, which is only used on vehicles that contain an expansion device called a capillary tube or accumulator. The accumulator serves as both a filter and a storage device for lubricant and coolant and is located on the low-pressure side of the system. This stock or reservoir of lubricant and refrigerant in the receiver drier ensures that no liquid passes from the refrigerant to the compressor. In other words, the filter driers take care of the entire refrigeration system of any air conditioning, be it for commercial, residential, industrial or vehicle use, so that particles, dust or any dirt enter the circuit while there is exchange of air with the outside.
Important considerations about filter driers
The system in which this piece is assembled is sealed to prevent the passage of polluting agents, dirt or dust. Therefore, every time the circuit is opened or every two years, it is necessary to replace the filter drier or accumulator. After a while, the inner layers that make up this desiccant and scrubbed part of the filter drier (and allow it to trap dirt) can wear out and lose their ability to work effectively with oil, refrigerant and dusty and dirty. Consequently, the entire system could collapse, since the operation of the filter drier is decisive for the proper functioning of the compressor and the cold that it can produce. Another factor to consider is corrosion caused by excessive moisture in the air conditioning system. This can drastically reduce compressor lubrication. That is, let condensation water, dirt or liquids pass into the rest of the circuit. The main causes of compressor failure and, in the worst case, of its stoppage, are unfiltered particles, garbage, metal shavings, etc. that circulate through the circuit. Likewise, if the filter does not trap moisture, the entire system may be exposed to corrosion and wear of all components and a considerable reduction in the useful life of the air conditioning.
How are filter driers installed?
When installing the filter drier, make sure that the direction of flow, which is indicated by an arrow on the label, is respected regardless of which side of the system this part is on. With the exception of reversible or bidirectional heat pump filter driers, all filter driers are made to operate with a unidirectional flow, which means they only have one inlet and one outlet. Failing to respect this is damaging the entire circuit completely and requiring major repairs or a new air conditioner. The primary goal of choosing a filter drier location is to ensure that the refrigerant and desiccant are in constant contact. This ensures that the air conditioning works properly and guarantees the durability of the air conditioning equipment. Below are some installation suggestions, both for the liquid line and the suction line, in order to achieve this constant contact:
The filter driers or dehydrators for the liquid line must be positioned correctly following the manufacturer's instructions and the specific model of the air conditioner. For the most part, refrigeration technicians see this as easy work and these parts work admirably. However, the following factors must be taken into account. It is not advisable to install loose filter driers (such as those made of silica) in a horizontal position. This is due to the fact that the granules are not compacted and have a tendency to accumulate at the bottom, leaving a part of the flow area exposed. The refrigerant has a tendency to create channels between the granules when placed horizontally, and the desiccant has little contact with the refrigerant, which alters the operation of the condenser and all the equipment. On the other hand, turbulence in the flow can cause the abrasion of the desiccant, generating a fine dust that cannot be collected by the filter and that can damage the valves, the cylinders and the pistons of the compressor. It is advised that they be mounted vertically, with the coolant flow going from top to bottom.
Remember that the refrigerant is in the form of a gas at low pressure and temperature on one side of the system and that its velocity is approximately six times greater than in the liquid line. It is therefore suggested that desiccant block type filter driers be installed on that side. A filter drier should normally be installed in the suction line vertically, with the flow from top to bottom. The main purpose of this is to ensure the return of the oil to the compressor. It has little to do with the desiccant. Oil can get trapped inside the filter drier capsule if it is placed in a horizontal position. Insufficient clearance or horizontal piping can be overcome by using 45° solderable copper elbows. On the other hand, a filter drier using a 90° bend in the suction line of a standpipe allows oil to easily enter the compressor without clogging. All this makes the circuit work freely and without obstructions of any nature.
What should be taken into account when installing filter driers?
In order to correctly select the appropriate filter drier for each type of air conditioning and for its correct installation, the manufacturer's recommendations must be followed to the letter.
In systems in which refrigerant charge is important, such as domestic appliances or window air conditioners, if the filter is made of silica or alumina, it can interfere with the system performance.
This happens because it reduces the amount of refrigerant that is circulating. In this case, the desiccants stagnate a part of the refrigerant. The result is that the filter drier will have to be as small as possible. It is best to buy the exact model air filter and not a generic one.
When removing seals from the passages of a filter drier, great care should be taken not to damage the donut or the surface. This should be installed in the system as quickly as possible after removing the seals.
If a filter drier is exposed for a long time without the seals on its connections, it cannot be installed in the circuit because it affects the operation of the air conditioning.
Care should be taken when handling filter driers so that they are not damaged, struck or cracked.