A Heat Station, also known as a District Heating Substation or a Hot Water Station, plays a crucial role in central heating and cooling systems by serving as an interface between the energy source and an independent area. It controls the heating and cooling of this area and measures energy consumption. Generally, heat stations do not produce energy themselves; instead, they utilize hot water from sources such as boilers, geothermal, district heating, and other similar energy sources, using control valves within them to meet the hot water, heating, and cooling demands of a unit or another independent space. Depending on the plumbing design and comfort requirements, heat stations can have various components and instruments, and we will briefly describe some commonly used equipment within the heat station below.
- Domestic Hot Water Heat Exchanger: Heat stations, if they do not contain a storage tank, supply a unit’s hot water needs based on the “instantaneous heating principle.” Therefore, the importance of the domestic hot water heat exchanger used within the station is very high. Total pressure drops within the unit, electrical consumption of the pump in the main system, return temperatures to the energy source, and consequently, consumption at the main energy source are all related to the heat exchanger used in the station.
When selecting domestic hot water, energy efficiency and comfort design requirements are considered, and the correct heat exchanger is chosen by examining LMTD (Logarithmic Mean Temperature Difference) and NTU (Number of Transfer Units) values.
- Thermostatic Control Valve: To maintain a constant water temperature, regardless of changes in the flow rate of the requested hot water, the thermostatic control valve is an essential component. The Kvs value of the thermostatic control valve should be at a point where it can meet the flow rate required to prepare hot water at the point where consumption is taking place. Otherwise, even if the correct hot water heat exchanger is selected, the desired comfort level for hot water use may not be achieved if sufficient flow cannot be supplied.
- Differential Pressure Valve: In systems where central energy sources heat or cool the water, and individual temperature control is carried out, meaning they have a variable flow rate and differential pressure regime, the correct operation of the system can only be achieved with differential pressure valves and proper regulation. Without proper regulation and control of variables, the entire system’s hydronic balance is disrupted, resulting in comfort issues and unforeseen energy consumption.
- Zone Valve: In situations where the capacity of domestic hot water is high (>75 kW), zone valves are used to statically limit the flow of heating/cooling lines. Zone valves provide a fixed flow limitation while also enabling control by a room thermostat using a thermal actuator. In fact, with the use of a smart thermostat, heating and cooling for the unit can be controlled via a mobile application.
