Refrigeration system:

Article link:

1. https://www.marineengineersknowledge.com/2020/08/operational-procedure-of-air.html

Sketch:

Direct expansion system:

.refrigeration system

→ evaporator coil situated inside the space to be refrigerated.

→ no duct and piping required

• The evaporator coil extracts the heat from the air inside.
• The compressor draws low pressure refrigerant vapour and delivers the high pressure refrigerant vapour through an oil separator to the condenser.
• The condenser liquefies the refrigerant.
• The liquid refrigerant from the condenser passes through the filter dryer, solenoid valve and thermostatic expansion valve to the evaporator.

Checks

Before starting the refrigeration plant, 

• Check the oil level in the crank case of the compressor.
• Insufficient oil wears down the components.
• In extreme cases, it may lead to seizure of the compressor.
• Check whether the cooling water inlet and outlet valves to the condenser are open.
• Insufficient flow of cooling water results in improper condensation which in turn increases the compressor discharge side pressure.
• Open the compressor outlet valve, condenser inlet valve, receiver outlet valve, filter drier inlet valve and outlet valves.
• Check whether power supply is available to the compressor motor.
• Ensure the compressor is in manual mode.

During start 

• Open the compressor inlet valve by half a turn and start the compressor.

• Open the compressor inlet valve slowly to fully open position.
• Change the operation of the compressor to automatic mode.
• Check the amperage of the compressor.

During operation:

• Check the compressor suction, discharge, and oil pressure.
• Inspect the compressor unit and check for any abnormality and vibration.
• Check the compressor oil level and check whether the oil returns from the oil separator to the crankcase

During auto Stopping:

• As the temperature reaches the set value, the thermostatic switch will cut off the compressor.
• The blower will continue to run.
• When the air temperature increases, the compressor will cut in.

To shut down for longer duration:

• To shut down for prolonged period, close the condenser liquid receiver outlet valve.
• The liquid refrigerant is collected inside the condenser receiver and the compressor stops due to low pressure.
• Shut the refrigerant line valves.
• Shut the condenser cooling water inlet and outlet valves.
• Switch off the power supply.