The most common type of electrode boiler pumps water from the lower part of the vessel to an internal header that has nozzles that allow the water to flow to electrodes. Generally the working pressure is maintained at 10 bar. If more pressure is needed the controls speed up the pump to increase flow through additional nozzles. As the needed pressure is reached the pump controls the flow of water to obtain the desired steam output at the desired pressure. On larger systems the pump can be controlled by a variable frequency drive so energy is not wasted. This control system can also control de-aerator pumps and controls. The electrodes are connected to a medium voltage AC source. Electrode boilers can work on both single phase and three phase supplies. If DC voltage is used, electrolysis of water occurs, decomposing water into its elements H2 at the cathode and O2 at the anode. The electrode boiler is 99.9% efficient with almost all the energy consumed producing steam. Losses are radiant heat from the vessel only. During the operation of the boiler, it is fed with water which contains conductive substances like salts. Because the departing steam is free of these substances, conductivity of water increases. With cleaner water in the boiler, the conductivity decreases. When conductivity rises beyond a set limit, some of the water must be removed and replaced with fresh water. The conductivity of the water and the voltage applied determine how much steam is generated in each stream of water.
As it doesn't directly generate pollution, no pollution control system is needed.
Unlike fossil fuel or conventional electric boilers, no boiler component is at high temperature except the water itself.
As compared to other boilers, electrode boilers experience little thermal stress.
The compact size of electrode boiler makes it easier to work with than other boiler types.
Low voltage transformers are not required due to which a medium voltage grid connection can be established.
Electric boilers have few components making it easier to control and maintain.
Dropping water levels inhibits current flow and allows the boiler to self-regulate.
Drawbacks
Due to the water serving as a conductor, the water becomes live at a significant portion of the input voltage. This creates a serious shock hazard when used, for example, to heat water for a bath or for tea making.
AC electric sources must be used, because DC electric sources leads to electrolysis of the water, breaking it down into its component hydrogen and oxygen.
Scale formation will insulate the electrodes which results in reduction of current and boiler output.
Safety measures
Water level should be maintained up to certain level and it should not be allowed to lower than that limit.
If water level falls below the limit level, current stops flowing as the circuit is not complete. This stops heating the water and producing steam.
