Hot water boiler intend for heating of bigger space such as chicken farms, green houses, shopping malls, furniture stores, workshops etc. He basic type variant is designed for operation with inside and outside air without any filters. Calorifier of this type is composed of hot water exchanger, axial fan with electric motor operation and adjustment shutters. Calorifiers are regularly produces in three sizes with three-line exchangers. We can produce them as one-line and two-line, and we can deliver calorifiers of a higher power.