Commercial heating and air conditioning is commonly referred to as HVAC systems, which stands for Heating, Ventilation and Air Conditioning systems. These systems are used for maintaining comfortable temperatures and air quality in homes and large buildings. The main purpose is to make the environment healthy and safe in terms of temperature and humidity. The laws of heat transfer, fluid mechanics and thermodynamics are used for designing.
HVAC systems are aimed at improving air quality, providing ventilation and maintaining pressure. Room air distribution methods are employed for delivering air. The ambient conditions and fresh air requirements must be specified whenever designing an HVAC system.
The heating systems used in HVAC can be any of the several kinds available. In cold areas, central heating is implemented. The system consists of a furnace, boiler and heat pump. Air control is maintained from a central location like a furnace or mechanical room.
Water is used as a medium for transferring heat. Pipes and ducts serve as passage for the heated fluid which is transferred to rooms through radiators. Radiators may be wall mounted or fixed under the floor.
The pump circulates water and ensures an equal supply of heat to all locations. If the weather is warm, the same pipes and ducts are used for cooling. The heating process may also be achieved through resistive heating. An electric current is used for heating conductive filaments.
There are a few considerations which should be kept in mind. Heat pumps are efficient but more expensive. They should be used in moderate climates only. Radiators should be situated near windows or in the colder parts of the building. Harmful gases are formed if the heating system is not working correctly. This is why proper ventilation is a must for every commercial heating and air conditioning system.
Ventilation is classified as mechanical or forced and natural. In the former kind, an air handler is used to control the air quality through dilution of inside air or substituting it with fresh air. Mechanical or forced ventilation is not energy efficient in humid regions.
In these areas, exhausts, direct drive fans are used for controlling air quality and humidity as well. In cold areas, ceiling fans can also be utilized to achieve ventilation. They circulate the warm air in the upper portion through the entire room.
Natural ventilation does not use any mechanical equipment. It ventilates a room with open windows, vents or openings in the wall. It works well only in small areas but is still widely used due to economical prices and no energy consumption.
Air conditioning systems remove heat from a room using radiation, convection and even heat pumps. The process is termed as the refrigeration cycle. The systems are designed not only to cool the area but also to ventilate it and control air humidity. Sophisticated designs employ a reversing valve which automatically switches between heating and cooling a room depending on the outside climate.
There are central cooling systems but they can be installed only when a building is being constructed. Retrofitting them in an already built structure is difficult because the ducts are very large. In such cases separate coils for indoors and outdoors can be used. The two units are connected through pipes, providing a passage for the refrigerant.
Dehumidification is important in air conditioning systems. Evaporators or open chiller cabinets are used for the purpose. Basements serve as good locations because water density is higher in the air at lower levels and temperatures. Filtering is also necessary for removing particle sand gases, which can be dangerous. The filtering and condenser coils must be cleaned regularly because the dirt built – up can damage the compressor.