Air Conditioning Plant- Starting, stopping

Air Conditioning Plant

The air condition plant for accommodation is generally a two-unit plant. Each unit comprises of a separate compressor, cooling and heating units along with other auxiliaries. Following procedure to be following for starting the AC system for accommodation:


  • Ensure air filter in the air handling unit is clean
  • Set the air damper so as to achieve the correct balance between fresh and recirculate air
  • Ensure the compressor sump heater is ON
  • All manual stop valves in the refrigeration lines are opened to full to avoid leakage from the glands
  • Check the oil level in the compressor sump
  • Open the steam for heater and humidifier
  • Open condenser cooling water valve
  • Start the water pump for cooling water unit
  • Ensure power is available for controller and starting panel of compressor
  • Check the setting of air handling control unit
  • Ensure expansion valve in the line is working fine as it will take control once the compressor starts
  • Press the start button in the panel. The compressor will start at its minimum capacity
  • Check for any abnormal noise from the crankcase or water carryover inside the crankcase during initial period of operation
  • During cooling down process the expansion valve controls the flow through the evaporator depending on the lowest allowable superheat temperature in the compressor suction line
  • When the cooling temperature is achieved, the expansion valve regulates according to supply air temperature
  • Ensure the oil in the return pipe of oil separator is warm


  • While running in the auto mode, the compressor will automatically start and stop depending upon the accommodation temperature
  • By pressing the stop or reset button, the compressor will stop
  • Isolate the compressor motor
  • Close the compressor suction valve
  • Close the compressor discharge valve
  • Shut the outlet valve of the condenser
  • Shut the inlet and outlet valves for cooling water line of condenser
  • Shut the steam supply to air handling unit

“ Ensure that all the drains of AC plant are clear as any blockage will lead to stagnant water. This can become the breeding ground of legionella bacteria which can have serious or even fatal consequences.”


The Ultimate Guide to Operating Procedures of Engine Room Machinery. Anish Wankhede [2014]

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