and Air Conditioning (Part II)


Fabrication of Ducting. The fabrication of HVAC ducting should incorporate energy efficient measures such as turning vanes at 90° bends and smooth transitions between ducting and components of different sizes or sections. Galvanic corrosion between galvanized steel and stainless steel should be prevented by isolating them from each other; this will save on duct / component replacement costs.

Diffusers and Grilles. The supply and extraction of the air to the rooms / offices can be made more efficient by using modern diffusers and grilles and improving airflow control. These ensure that the optimum amount of air is admitted and extracted from the rooms, promoting more uniform room temperatures.

Heating and Cooling Methods to Upgrade HVAC. Hot or cold air is supplied to the building by the fans that draw the air through coils in the air handling unit. Large commercial buildings use hot water as supplied by a furnace to circulate through the coils producing hot air and cold water from chillers being used for the air conditioning. Both these methods have been in use for some time, but modern appliances have seen efficiency rise by 20%, therefore the modern furnaces and chillers should be examined. One of the biggest energy efficiency savings in heating and cooling can be achieved by using a heat pump. In the hot air mode, refrigerant gas is circulated around the coils of the heat pump condenser located in the AHU. When the fans draw the air over the coils. the refrigerant condenses to a liquid, giving up its heat to the air. The fans then discharge the hot air to the building. In the air conditioning mode the system is reversed by a reversing valve; the coils in the AHU act as an evaporator, with liquid refrigerant being circulated through the coils this time. The air is drawn over the coils by the fans, evaporating the refrigerant and converting it back to a gas. This removes the heat from the air before being discharged by the fans to the building.

This system can be made even more efficient by the use of geothermal energy in the form of a geothermal heat pump, which is suitable for large buildings provided there is the ground-space to locate the buried pipe loops. Vertical loops take up less space, but these are more costly to install than their horizontal counterparts. During the winter months, the heat pump uses the heat from the underground loops to evaporate the refrigerant. This heat from the refrigerant gas is transferred to the air that is then used to heat the building. In the summertime the heat pump is used to cool the air by dissipating the heat from the building back into the ground through the geothermal loops. Heat pump components for use in commercial buildings are continuously being upgraded. For instance, modern screw or scroll compressors are much more efficient than the standard reciprocating ones.

Control Systems. Modern HVAC management control systems can also improve the efficiency of the system. The control system constantly monitors the temperatures and pressures of the air at strategic points throughout the HVAC system. Ducting static air pressure monitoring and control are fulfilled through automatic adjustment of circulating fans / dampers, (also detects air leaks).

Electronic Programmable Thermostats. These automatically control pre-set, comfortable temperatures both during working hours, and when building is unoccupied, reducing energy and increasing overall plant efficiency.

Zone sensors. These are sensors for control of air quality and quantity supplied to the different zones or areas of the building, e.g. offices, rest rooms, conference rooms, executive suites, canteens, and cafeterias.



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