Hydronics

Hydronics () is the use of liquid water or gaseous water (steam) or a water solution (usually glycol with water) as heat-transfer medium in heating and cooling systems. The name differentiates such systems from oil and refrigerant systems. Historically, in large-scale commercial buildings such as high-rise and campus facilities, a hydronic system may include both a chilled and a heated water loop, to provide for both heating and air conditioning. Chillers and cooling towers are used either separately or together as means to provide water cooling, while boilers heat water. A recent innovation is the chiller boiler system, which provides an efficient form of HVAC for homes and smaller commercial spaces. District heating Many larger cities have a district heating system that provides, through underground piping, publicly available high temperature hot water and chilled water. A building in the service district may be connected to these on payment of a service fee. Hydronic systems can include the following kinds of distributions: Chilled water systems Hot water systems Steam systems Steam condensate systems Ground source heat pump systems Hydronic systems are further classified in five ways: Flow generation (forced flow or gravity flow) Temperature (low, medium, and high) Pressurization (low, medium, and high) Piping arrangement Pumping arrangement Hydronic systems may be divided into several general piping arrangement categories: Single or one-pipe Two pipe steam (direct return or reverse return) Three pipe Four pipe Series loop In the oldest modern hydronic heating technology, a single-pipe steam system delivers steam to the radiators where the steam gives up its heat and is condensed back to water. The radiators and steam supply pipes are pitched so that gravity eventually takes this condensate back down through the steam supply piping to the boiler where it can once again be turned into steam and returned to the radiators. Despite its name, a radiator does not primarily heat a room by radiation.