What characterizes a heating boiler according to the definitions provided?

The definition of a heating boiler is characterized by its capability to produce steam at a specific pressure. A heating boiler specifically produces steam at a pressure of 103 kPa (15 psi) or less. This is significant because it distinguishes heating boilers from other types of boilers that may operate at higher pressures, including those which produce steam for industrial processes or electricity generation.

The pressure threshold is key to understanding the classification of boilers. Heating boilers are typically used for space heating, water heating, and other similar applications where low-pressure steam is sufficient. Maintaining pressure below 103 kPa ensures safety and matches the requirements for residential and commercial heating systems.

Other definitions provided may refer to higher pressures or specific conditions not typical of heating applications, which would not align with the characteristics of a heating boiler. This helps clarify why the correct answer emphasizes a steam production pressure that is at or below 103 kPa, aligning perfectly with standard definitions used in power engineering.