Katla segamissõlm
The mixing unit is a device based on the thermocouple operation, which is installed between the boiler and the accumulation tank for keeping the boiler operating temperature automatically. The mixing unit is especially useful for solid fuel boilers. Keeping the correct boiler temperature and increasing the fast temperature after ignition will significantly reduce the boiler's corrosion and soot, as the condensation time from the boiler and the smoke pipes heating up will reduce to to ten times ( NB! 5 mm soot on the boiler wall eaquals about 15 mm thickness layer of stone wool ) The use of the mixing unit prevents the formation of micro-cracks and consequently the leakage or breakage of the boiler.
Starting
It is advisable to control (start and stop) the mixing unit circulation pump using a contact thermometer located on the smoke duct. If the boiler lights up, the flue gas contact thermometer turns on the circulation pump. Therefore, if the flame goes out in the boiler, the flue gas temperature drops, and when it falls to the minimum regulated value of the contact thermometer, the pump switches off.
Working principle
The thermostatic valve of the mixing unit warms up by the returning hot water from boiler. 
When warming up, the thermostatic valve opens and allows cool water in from return line. The thermal opening depends on the temperature of the water around the thermocouple, which means that the temperature of the water from the thermostatic valve is always kept constant. Generally, thermocouples operating at 61C, 72C are used. The return temperature of the boiler is maintained at a temperature between 60 and 65 ° C. Due to the pressure generated by the circulation pump, the reflux stop valve (TERMOBAC) closes by blocking the cool water coming back from the battery tank or the heating system directly to the boiler. However, the hot water coming from the boiler is pumped through the thermostatic valve back to the boiler. Water only moves in the small circle of the boiler. The boiler is heating up quickly and evenly.
Free flow
If the circulation pump is stopped (in the event of a power failure etc), the water pressure from the pump will drop, causing the shut-off valve to open due to natural circulation, thus allowing the system to circulate naturally, protecting the boiler from overheating and breaking.
© 2002 Guides on the ACASO AB website.
