All-Air systems

There are Three main types Hvac Systems
Equipment and systems generally fall into three main types, all-air, all-water and all-refrigerant, however, in every case, refrigerant is used as the final cooling source or medium.

Most systems these days are also referred to as air cooled, as opposed to water cooled. That is, the final rejection of heat to external atmosphere is via air, using a dry coil and fans. Water-cooled systems use a cooling tower and if this is not properly maintained can lead to problems with legionnella or legionnaires disease.

All-Air systems
All-air systems transfer cooled or heated air from a central plant via ducting, distributing air through a series of grilles or diffusers to the room or rooms being served. It normally comprises the cheapest equipment cost, but is not necessarily easy or cheap to install in a building due to the size of ducting required and the cost to install. It can be a problem to control temperature properly, and the system may be energy inefficient. All-air is generally rated in second place compared to other systems in relation to the amount of energy used to achieve the desired result.