Basic large volume sanitary water boiler heater are installed in the lowest zone of the boiler. It is mostly at the place of the water heater inspection opening or at the place provided by the water heater manufacturer and serves to heat the entire volume of the water heater. In order to shorten the time of heating the entire amount of water, additional heaters are added to the basic heaters as an auxiliary means.

Additional large volume sanitary water boiler heater is installed in the central zone of the tank, which is generally located above half of the boiler, so we can say that it is the upper third of the boiler. Considering that the heaters are installed in the upper zone of the water heater, they serve to quickly heat a small amount of water so that users can get hot water in the shortest possible time. Additional heaters also serve as an auxiliary means to the basic electric heaters, given that when the set temperature is reached in the upper zone of the sanitary water heater, the additional electric heater is turned off, and the basic heater continues to work until the set temperature is reached in the lower zone of the water heater.