Which of the following statements is true about heating boilers?

Heating boilers are designed to operate continuously at full load for maximum efficiency. When a boiler is running at full capacity, it can achieve optimal thermal efficiency because it is designed to convert fuel to heat at the best possible rate under stable operating conditions. This continuous operation allows for better management of heat output and minimizes energy losses that occur during start-up, shut-down, and varying load conditions.

While boilers can sometimes handle varying loads, their design philosophy emphasizes efficiency through consistent, high demand operation. This focus contributes to less energy waste and better thermal performance, making them suitable for applications where constant heat output is required.

The other statements do not align with the primary operational design and characteristics of heating boilers. For example, while some modern designs aim for space efficiency, traditional heating boilers are often not more space-saving than conventional boilers. Additionally, although heating boilers can be used in industrial processes, they are also widely utilized in residential and commercial settings, thus not limited to industrial use only.