When in operation the internal temperature of the chamber tends to drop to the desired temperature, called the set point, when this value is reached, the thermostat turns off the solenoid valve which is responsible for allowing or not the refrigerant to pass to an expansion valve. . When turned off the solenoid valve prevents this flow of refrigerant through the liquid line, causing the pressure in the evaporator and suction line to drop as the compressor at this time continues to operate by collecting refrigerant from the low side of the system to the high side, accumulating it from the compressor discharge through the condenser and liquid tank to the solenoid valve.
The suction pressure is monitored by a low pressure switch that will shut down the compressor as soon as this pressure reaches the preset value, stopping the machine.
During this “temperature” shutdown, the evaporator forks remain actuated to ensure “cold” air circulation in the chamber's internal environment. The internal temperature will tend to rise, due to heat exchanges from various sources, the solenoid valve will remain off blocking the liquid line until the internal temperature does not exceed the thermostat differential temperature value.
When this temperature is reached the thermostat activates the solenoid valve thus allowing the passage of refrigerant that migrates from the high side to the low side due to the pressure difference, thus the suction pressure tends to increase. When the suction pressure rises to a value equal to or greater than the low pressure switch differential pressure, it releases the operation of the compressor motor which resumes the refrigerant cycle thus causing the cooling effect again.
