Refrigerant Pressure Sensor / Switch: Description and Operation

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)




1. 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 kg/sq.cm, 27 psi) < P < approx. 2,154 kPa (22 kg/sq.cm, 313 psi)
When refrigerant pressure is greater than 176 kPa (1.8 kg/sq.cm, 25.5 psi), diaphragm spring is inverted so that low switch is opened (OFF).




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