Receiver Dryer: Description and Operation

Receiver Drier

MECHANISM

The amount of refrigerant circulating varies with the heat load changes. The receiver drier supplies the amount of refrigerant necessary for the cycle according to such changes.




1. It removes bubbles from the condensed refrigerant so that only liquid refrigerant may be delivered to the expansion valve. (If bubbles are present, the refrigerant passing through the expansion valve varies in quantity, temperature, and pressure, resulting in insufficient cooling.)
2. It removes moisture from the refrigerant.
3. It removes foreign substance from the refrigerant.
4. It permits a visual observation of the amount of refrigerant through the sight glass. The receiver-drier consists of a strainer to remove foreign substance, desiccant to absorb moisture from refrigerant, a sight glass to check the amount of refrigerant.

DUAL SWITCH




The dual switch is located in the high-pressure line of the refrigeration cycle. It consists of a diaphragm which receives pressure, diaphragm springs, pin and contact points. Two types of contact points are used. One type activates when the internal pressure is low or when it is too high while the other type controls the operation of the condenser fan.

- Prevention of operation when there is no gases in the line due to absence of refrigerant (during low-pressure operation)
- Protection of refrigeration cycle from abnormal refrigerant pressure rise - (during high-pressure operation)

ABNORMAL LOW-PRESSURE OPERATION




- All contact points are open (OFF) since the tension of the diaphragm springs is greater than refrigerant pressure.
- Approx. 186 kPa (1.9 kgf/sq.cm, 27 psi) < P < approx. 2,154 kPa (22 kgf/sq.cm, 313 psi)

When refrigerant pressure is greater than 176 kPa (1.8 kgf/sq.cm, 25.5 psi), diaphragm spring is inverted so that low switch is opened (OFF).


ABNORMAL HIGH-PRESSURE OPERATION




When refrigerant pressure is greater than 2,746 kPa (28 kgf/sq.cm, 398 psi), diaphragm spring is inverted so that high switch is opened (OFF) and low switch is closed (ON)