Which of the following types of boilers is classified as a "Heating Boiler"?

A "Heating Boiler" is specifically designed for providing heat to a space or for process heating through hot water or steam. In this context, the hot water supply boiler is categorized as a heating boiler because its primary function is to supply hot water for heating purposes. These boilers provide heat to residential and commercial buildings, making them essential for maintaining comfortable temperatures.

On the other hand, the other types of boilers mentioned do not fit into the "Heating Boiler" classification. A flue gas boiler is not designed primarily for heating; instead, it uses exhaust gases for heat recovery and efficiency improvements. A condensing boiler is primarily aimed at maximizing energy efficiency by condensing water vapor in flue gases, but it may not specifically denote the function of heating in the same way. Lastly, the term "heating value boiler" typically refers to the energy content of fuels rather than a classification of boiler types, making it irrelevant to this question.

Therefore, the hot water supply boiler is accurately recognized as the type that classifies as a "Heating Boiler."