What are the two general designs of electric boilers?

Electric boilers are primarily categorized into two general designs: electrode and immersion.

In electrode boilers, the heating elements are immersed directly in the water, and the water itself conducts electricity. When voltage is applied, the resistance of the water creates heat, leading to the boiling of water. This type of boiler is efficient for applications requiring rapid heating and can operate effectively in various operational conditions, provided the water conditions are properly controlled.

Immersion boilers, on the other hand, consist of heating elements that are typically mounted in a manner where they are surrounded by water but not directly immersed in it. The heating elements transfer heat to the water through conduction and convection. This design allows for a more controlled heating process, suitable for steady-state applications.

The other options present different characteristics that do not accurately define the general designs of electric boilers. Grounded and ungrounded relate to electrical safety rather than boiler design. AC and DC refer to different types of electrical current rather than boiler configurations, and firetube and watertube are designs for steam boilers, which can be fueled by various energy sources, not specifically for electric boilers. Thus, the classification of electric boilers indeed centers on the electrode and immersion designs.