An electric steam boiler is a steam generation unit which utilizes the thermal energy developed by electric elements to heat water inside an enclosed tank or shell. Apart from its heat source, the electric steam boiler is similar in its basic construction and operation to other types using gas or oil furnaces to heat the water. These boilers fall into two categories — resistance and electrode —, types defined by the elements used in their design. Resistance boilers feature conventional resistive immersion elements similar to those used in a kettle while electrode types utilize a current passed through the water between two electrodes to provide a heat source. Although they are more costly to run, electric steam boilers offer operators several benefits over gas and oil types, including zero emissions, no fuel leakage concerns and ease of use.
Steam generation for food processing facilities, laundries and hospitals is generally achieved using a steam boiler. Similar in construction to a conventional water heater, these boilers use a thermal energy source to boil water in an enclosed tank to generate steam. The heat source may be a gas or oil flame or, in the case of an electric steam boiler, a set of electric elements. Electrically-heated boilers are fairly costly to run, but offer many benefits which offset the costs involved. These include simple operation, low maintenance requirements, and zero emissions.
The resistance element electric steam boilers feature one or more resistive immersion elements. These elements are similar to those used in a kettle and consist of a resistive core enclosed in a sealed tube. The elements are usually long, U-shaped units passed through a bulkhead or flange bolted onto the boiler body, placing the connections on the outside of the boiler with the element immersed in the water inside the tank. When an electric current is applied to these elements, the resistance offered to its passage by the element cores causes them to heat up which, in turn, heats the water.
Electrode boilers have far higher outputs than resistance types and utilize a set of conductive rods or electrodes immersed in the boiler water. When an electric current is applied to the electrodes, the water becomes a conductor and resistive element to the passage of current between the two. This causes the water to heat up in the same way as the resistive core in the immersion element does. This type of electric steam boiler is generally used where large steam volumes are required and are capable of producing up to 110,000 lbs. (242,000 kg) of steam per hour. Resistive element boilers generally produce less steam with average values ranging between 50 and 13,000 lbs. (110 and 28,600 kg) per hour.