The THERMIS heat exchangers are energy-saving thermal devices that exploit the temperature of the boiler’s flue gases.

They were developed to comply with the European Directive 813/2013, which mandates an increase in boiler efficiency based on the higher heating value of the fuel, as opposed to the lower heating value that was the point of reference in the past. Furthermore, according to the directive, there is a control on the quality of flue gases, and one of their main components, NOx, is reduced to below 120 mg/kW for oil combustion and 56 mg/kW for Natural Gas combustion.

As evident from the above, the primary objective of Directive 813/2013 is environmental protection and, by extension, energy savings.

Thus, the exchanger acts as an extension of the boiler.

The THERMIS heat exchangers function best when the return water of the installation passes through the exchanger from one side and the boiler’s flue gases pass through from the other.

The temperature drop of the flue gases within the exchanger is significant, and the exit temperature from the exchanger is around 90°C at full boiler load, with water inlet – return temperatures of 80-60°C.

At water inlet – return temperatures of 50-30°C, the temperature of the flue gases is around 50°C, where the condensation process occurs.

The above results from our measurements, as well as according to the results obtained during the certification of our boilers at the National Technical University of Athens.

The “THERMIS” exchangers come in three types of construction:

a) Vertical type, with Inox tubes through which the flue gases pass and are surrounded by the installation water.

Power range 30-500 kW

b) Plate type, with specially shaped Inox panels within a suitable casing. The installation water passes through the panels, and the flue gases pass outside them.

Power range 30-145 kW

c) Spiral type, with specially shaped Inox tube within a suitable casing. The installation water passes through the tube, and the flue gases pass outside it.

Power range 20-45 kW

They are tested under a hydraulic water pressure of 8 bar and operate at pressures up to 4 bar. The material of the final chimney must be inox or PPF 120°C.

An essential component of the exchanger is the siphon for the outlet and disposal of condensates.

The Inox siphon, located at the bottom of the exchanger, must be filled with water before starting the system. The siphon can be filled through the exchanger, from a chimney orifice.

By applying these exchangers, compliance with Directive 813/2013 is achieved, and an energy saving of up to 20% is realized.