Heating, ventilation, and air conditioning, that is HVAC for substation. This topic explains about importance of HVAC system, air conditioning and ventilation, steps involved in HVAC design, HVAC equipment selection criteria. Importance of heating, ventilation, and air conditioning system, that is, HVAC in substation: improves the efficiency of the electrical equipment in the substation, provides dust and noise-free environmental conditions, provides thermal comfort, increases productivity by maintaining the constant and workable temperature inside , circulates clean, filtered, healthy, comfortable air in the working premises, avoids ingress of outset foreign particles into the room. Avoids malfunctioning of sensitive electrical panels in control rooms, removes stale air and fouling smell inside the room. Air conditioning is the process of controlling temperature, humidity, air movement and a quality in an enclosed space irrespective of outside conditions. Unit of measurement for air conditioning system is tons of refrigeration. That is TR. One ton of refrigeration is equal to 12,000 British thermal unit per hour. That is BTU/hr. One ton of refrigeration, that is one TR, consumes electrical power in the range of 0.95 kilowatt to 1.4 kilowatt. The following split type air conditioning system are mostly used in domestic substations; high wall split type AC units and Cassatt type AC units. Ventilation introduces fresh air in a confined environment to improve indoor air quality by diluting and displacing indoor pollutants. Ventilation system types. Natural ventilation, by natural means of a draft and differential pressures. Forced ventilation, forced through mechanical means by fans. The types of ventilation fans are centrifugal fans, axial flow fans. Applications of forced ventilation system in substation are; smoke extract system, stairwell pressurization, battery room, toilet, and kitchen exhaust. The HVAC practices in domestic and the Middle East are given in the table. The onscreen table contains the inside design criteria for air conditioning and ventilation. The steps involved in the HVAC design are the heat load estimation derived from inputs like equipment heat dissipation, number of personnel, heat emitted by lighting, solar gains from walls and roofs, etc. Ventilation airflow rate calculation. Ducting layout preparation, AC equipment selection, ventilation equipment selection. Next, we see the relation between heat dissipation and air conditioner capacity. Heat dissipated by equipment and occupants is directly proportional to the capacity of air conditioning system. An increase in total heat dissipation will increase the air conditioner capacity significantly. Parameters required for the selection of air conditioning units, tonnage, that is TR, dehumidified air quantity, that is cubic feet per minute, CFM. TR and CFM are obtained from heat load calculation. External static pressure, ESP in millimeters of water column. ESP is calculated based on duct pressure loss, filters, diffusers, and dampers. Two in 200 percent, that is one into 200 percent working, plus one into 100 percent standby, or three into 50 percent, that is, two into 50 percent working, plus one into 50 percent standby. Number and capacity of standby units shall be chosen based on selected configuration and budget allocation. Parameters required for the selection of ventilation funds : air quantity, that the CFM. CFM is obtained based on air changes method or temperature rise method calculation. External static pressure in mm of water column. ESP is calculated based on duct pressure loss, filters, diffusers, and dampers. Here is a quick recap of what you have learned thus far. Importance of heating, ventilation, and air conditioning system, that is, HVAC in substation: improves the efficiency of the electrical equipment and provides dust and moist free environmental conditions, provides thermal comfort, avoids malfunctioning of sensitive electrical panels in control rooms. Air conditioning is the process of controlling temperature, humidity, air movement, and air equality in an enclosed space irrespective of outside conditions. Ventilation introduces fresh air in a confined environment to improve indoor air quality. Natural and forced ventilation are the types of ventilation system. TR, dehumidifier air quantity, and external static pressure are the main parameters required for the selection of air conditioners. Air quantity and external static pressure are the main parameters required for the selection of ventilation fans.
