Heating is the forced warming of a room up to the required temperature. In the cold season a heating system compensates heat loss of the building, maintains comfortable temperature in living and public premises, and creates the conditions required for uninterrupted work of industrial and engineering sites.
A heating system consists of a heat generator (heat source), heating pipelines (media conduits) and heaters (medium-to-air heat transfer appliances). The latter include stoves, solid fuel boilers, gas boilers and electric boilers, as well as radiators connected to the central heating system. Underfloor heating, infrared heaters, heat pumps and solar collectors are alternative heating solutions.
According to the heat source location relative to the heated room, a heating system can be:
- Central heating system with the heat source (boiler room, CHP, etc.) outside the heated room, covering several premises or entire buildings at the same time
- Local heating system with the heat source and heat appliance at the same premises
By heater design, the heating systems can be classified as follows:
- Radiant systems with heating through heat radiation by the heater
- Convective systems with heating through air warming up and convection around the heater
The heating systems differ by the circulating heating medium:
1. Water. Water heating systems can be classified by the maximum water circuit temperature as follows:
- Low-potential systems with the maximum water temperature not above 65°C (solar heating, heat pump systems)
- Low-temperature systems with the maximum water temperature not above 105°C
- High-temperature systems with the maximum water temperature up to 150°C
2. Steam. Steam heating systems can be classified by the steam pressure as follows:
- Vacuum steam heating systems with the absolute steam pressure not above 0.1 MPa and maximum steam temperature not above 100°C
- Low-pressure heating systems with the absolute steam pressure not above 0.17 MPa and maximum steam temperature not above 115°C
- High-pressure heating systems with the absolute steam pressure up to 0.3 MPa and maximum steam temperature up to 132°C
3. Air at 45°C to 70°C
4. Electricity
5. Gas
6. Combination of several media
By the medium circulation method, the water and steam heating systems are classified as:
- Natural-circulation or gravity heating systems where the turnover is driven by the difference in the density of cold and hot media
- Forced circulation heating systems, or pump-driven systems, use pumping equipment to build pressure
In addition, according to the arrangement of heater connection pipes, a water or steam heating systems can be:
- Vertical heating system. Vertical heating conduits include mains, risers and connecting pipes to and from the heaters: hot water/steam inlets and cooled water/steam outlets, respectively
- Horizontal heating system
The water and steam heating systems can be classified by the medium flow direction as follows:
- Heating systems with co-current water flow, where the medium in the supply and return mains flows in the same direction
- Heating systems with dead-ended water flow, where the medium in the supply and return mains flows in opposite directions
There are different heating system designs as to riser arrangement and heater connection techniques:
- Single-pipe
- Double-pipe
- Bifilar heating systems which supply medium at different temperatures to one or more heaters in the same room
Also, heating can be either periodic (seasonal) or all-season.
