Four types of fluids are used in heating systems. Heating systems are named according to the types of fluids that provide the transport of heat energy.

Hot Water Heating System : Although the cost is cheap, the fluid that carries the heat best is water. They are systems with leaving water temperature up to 110°C. Today, hot water heating systems are generally used in building heating. Hot water heating systems are generally designed for 80 degrees flow and 60 degrees return temperatures. If an underfloor heating system is to be built, 55 degrees of flow and 45 degrees of return temperatures are taken.

Superheated Water Heating System: These are the systems where the leaving water temperature is above 110 degrees. It is used in large-capacity district heating and process heating.

Steam Heating System: It is preferred in large facilities and process heating, due to its high temperature and high heat transfer feature.

Hot Oil Heating System: When the water temperature increases, the pressure of the installation carrying the heat increases in parallel. Costs increase due to the increase in installation pressure. Additional safety requirements must be met. For these reasons, it is preferred in process heating where high temperature is required.

In comfort heating systems, low temperature boilers are generally used. High efficiency condensing boilers should be used in natural gas fired heating systems where the return water temperature is below 50°C. In order to increase efficiency in comfort heating systems, programmable automation systems that work depending on outside and indoor air temperatures, proportionally controlled burners, economizers, circulation pumps with frequency inverters, thermostatic control equipment in heated spaces, heat recovery devices, insulation materials with low heat permeability calculated in accordance with standards should be used.