Air Conditioning and Heating R-12 All Caterpillar Machines – Receiver-Dryer



Illustration 1 g00358258

Refrigerant Flow Through Air Conditioning System

(1) Compressor

(2) Condenser Coil

(3) Receiver-Dryer

(4) Expansion Valve

(5) External Equalizer Line

(6) Evaporator Coil

(A) Air conditioner refrigerant as a high pressure, high temperature vapor

(B) Air conditioner refrigerant as a high pressure, high temperature liquid

(C) Air conditioner refrigerant as a low pressure and low temperature liquid

(D) Air conditioner refrigerant as a low pressure and low temperature vapor



Illustration 2 g00645942

Typical Receiver-Dryer

(3) Receiver-dryer

(7) Quick coupler

(8) Low pressure cutoff switch

(9) Relief valve

(10) Filter

(11) Desiccant



Illustration 3 g00645970

Top View of Receiver-Dryer

(3) Receiver-dryer

(7) Quick coupler

(8) Low pressure cutoff switch

(9) High pressure relief valve

(12) Moisture indicator

(13) Sight glass

The liquid refrigerant under high pressure and under high temperature leaves condenser coil (2) and passes through receiver-dryer (3). The liquid refrigerant inside the receiver-dryer passes through filter (10) and desiccant (11). The desiccant will absorb a small amount of moisture.

Receiver-dryer (3) will also store a small amount of refrigerant. This stored refrigerant is used in order to compensate for the changing system demands. The demands can result from different speeds of the compressor and small losses of refrigerant.

Note: Receiver-dryer (3) must be replaced annually. Receiver-dryer (3) must also be replaced whenever the system is opened. Receiver-dryer (3) should be replaced if moisture indicator (12) is filled with moisture. Moisture indicator (12) will display a pink color or white color if the receiver-dryer is full of moisture.

Some receiver-dryers are equipped with quick couplers (7). Receiver-dryers that have quick couplers can be removed and installed without recovering the refrigerant in the air conditioner system. Refer to Disassembly and Assembly, “Receiver-Dryer – Remove and Install”.

High pressure relief valve (9) is located on most receiver-dryers. The valve allows the refrigerant to be released to the atmosphere if the pressure increases to approximately 3450 kPa (500 psi).

Most receiver-dryers (3) will have low pressure cutoff switch (8). If the system pressure lowers to approximately 175 kPa (25 psi), the switch will open. This will open the electric circuit to the magnetic clutch and the compressor will not operate. The low pressure cutoff switch (8) is used in order to detect a low refrigerant charge. The low pressure cutoff switch (8) is used in order to detect system operation at a temperature below 0 °C (32 °F).

Moisture Indicator

Some air conditioning systems will have moisture indicator (12). This moisture indicator is used in order to determine the relative moisture in the system.

The system must be operated for 2 to 3 hours from time of installation before the system is checked for moisture. Look at moisture indicator (12). If the moisture indicator is blue, the system is dry. If the moisture indicator is pink or white, the system is full of moisture.

If the system is full of moisture, the moisture must be removed. Refer to Disassembly and Assembly, “Receiver-Dryer – Remove and Install”.

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