Question

How do the operating controls for hot water boilers compare to those used for steam boilers in terms of their construction and application? What causes the bellows of these controls to actuate in the case of hot water boilers?

Answer 1

Hot water boilers use an aquastat as the main control device, while steam boilers use a pressuretrol. The bellows of the aquastat actuate based on the expansion/contraction of a liquid-filled bulb sensitive to temperature changes.

Step-by-step explanation:

The operating controls for hot water boilers differ from those used for steam boilers in terms of construction and application. Hot water boilers typically use a aquastat as the main control device, while steam boilers use a pressuretrol. These controls are responsible for controlling temperature and pressure, respectively. In hot water boilers, the bellows of the aquastat actuate based on the expansion or contraction of a liquid-filled bulb, which is sensitive to temperature changes. When the temperature of the water rises above or falls below the set point, the bellows expand or contract, causing the aquastat to activate the boiler's burner or circulator.