What type of boiler has sections stacked on one another?

The correct answer is a vertical sectional boiler. This type of boiler is designed with sections that are arranged vertically, allowing for a more compact design and efficient use of space. The vertical arrangement facilitates easier maintenance and can lead to enhanced natural circulation within the boiler, ensuring more even heat distribution and improved performance.

In a vertical sectional boiler, the configuration typically allows multiple sections to be stacked on top of each other, optimizing the height of the installation area. This is particularly beneficial in situations where space is limited, such as in smaller facilities or older buildings.

The other types of boilers, while having their unique designs and advantages, do not conform to the vertical stacking of sections. Horizontal sectional boilers, for example, are laid out with the sections arranged side by side. Combination boilers may incorporate features of both types but do not specifically refer to the vertical stacking characteristic. Lastly, a single-stack boiler design usually means it has one stack for exhaust and doesn't imply a sectional arrangement.