5　Air Conditioning

5.1　General Requirements

5.1.1　Air conditioning shall be provided for the following plant buildings and auxiliary rooms when the normal heating and ventilation used for them cannot meet the requirements for the room temperature，relative humidity，etc.:

a）Production building which is required by the production process to have special requirements for the indoor temperature and humidity.

b）Rooms with higher service requirements，e.g.，distributed control system（DCS）control room，central control room（CCR），field auxiliary room（FAR），conventional instrument control room，on-line analyzer room，physical properties testing room，precision instrument room etc..

c）Rooms whose doors and windows are not allowed for frequent opening due to severe surrounding environment.

d）Rooms for production operation and management with personnel comfortableness requirements.

e）Rooms where heating and ventilation systems，if used，can satisfy comfort and temperature and humidity requirements.

5.1.2　Floor area of air-conditioned rooms and heat dissipation or wet loss in air conditioned rooms shall be minimized whenever possible，provided that the service requirements are met.Where local air conditioning or spot air conditioning can satisfy the service requirements，entire-room air conditioning shall not be used.If different basic values are selected respectively in winter and summer for the air conditioning systems and satisfy the service requirements，these basic values of room temperature and relative humidity shall be used.If specified temperature and humidity are only required to be maintained in the lower spaces of tall and wide production buildings，layer-wise air supply or lower air supply should be used.

5.1.3　Air-conditioned rooms should be grouped.Process equipment，apparatuses and instruments requiring same basic values and accuracy of room temperature and relative humidity should be arranged in the same air-conditioned room.Air-conditioned rooms requiring similar basic values of room temperature and relative humidity should be adjacently arranged.

5.1.4　Air-conditioned rooms should be arranged away from the locations generating vibration，large noises，or huge dust or corrosive gases.

5.1.5　Unit air conditioners may be installed in air-conditioned rooms，provided that the required noise level，vibration level and watertight performance and airflow distribution are met.

5.1.6　Air conditioning unit and refrigeration unit should be of mechatronics.

5.1.7　Air temperature，relative humidity and cleanliness in air-conditioned rooms shall be determined according to process units，instruments and control systems，analysis instruments and health requirements.

Air temperature，relative humidity and maximum allowable concentration of harmful substances in control rooms without special requirements may be selected from Table 1 below:

5.1.8　Air-conditioned rooms without harmful substance shall be maintained at a positive pressure not greater than 50Pa.

5.1.9　Artificial refrigeration methods for air conditioning service shall be determined through technoeconomic comparisons according to refrigeration capacity，power supply source，water supply source，heat source and building services.Thermal-powered refrigeration systems should be used for any one of the following conditions:

a）Excess heat sources are available in the plant.

b）Heat supply is surplus in the plant in summer.

5.1.10　Heat transfer coefficient of building envelopes shall be determined through techno-economic comparisons according to building services and air conditioning categories.For process air conditioning service，heat transfer coefficient of building envelopes shall not be larger than that defined in Table 2 below，and for comfort air conditioning service，it shall conform to the applicable national design codes and standards for energy conservation.