The dry filter is generally installed behind the liquid reservoir and in front of the sight glass, stop valve, and thermal expansion valve; there are two locations in the suction pipe:

1. Between the gas-liquid separator and the compressor;

2. Between the four-way valve and the gas-liquid separator.

It is best to install the filter dryer between the four-way valve and the gas-liquid separator:

1. If impurities enter the suction pipe, it may block the oil return hole filter of the gas-liquid separator. This can be avoided if there is a filter drier in front;

2. The gas-liquid separator is required to be installed as close as possible to the compressor.

For the filter drier in the liquid pipe of the heat pump system, there are some special installation requirements because it requires bidirectional flow. In practical applications, there are the following common designs:

1. Only installed on the refrigeration cycle;

2. Use four one-way valves to install the liquid reservoir, filter dryer, and expansion valve on the public pipeline, so that both cooling and heating can be used;

3. Use two one-way valves and two dry filters to work in the cooling and heating cycles respectively;

4. Use a two-way filter dryer.

In addition to the drying and filtering work of the normal refrigeration system, the filter dryer also has an important function of cleaning the system after the compressor burns out.