Question

What firing control will prevent thermal shock to a hot water boiler?

a) a low limit control
b) an operating control
c) a high limit control
d) none of the above

Answer 1

A high limit control is the firing control that will prevent thermal shock to a hot water boiler.

Step-by-step explanation:

The firing control that will prevent thermal shock to a hot water boiler is a high limit control. A high limit control is a safety device that shuts down the burner if the temperature in the boiler exceeds a set limit. It prevents the water from overheating and causing thermal shock, which can lead to damage in the boiler.

When the temperature reaches the high limit, the high limit control will signal the burner to shut off, preventing further heating. Once the temperature drops below the set limit, the control will allow the burner to restart and provide heat to the boiler again.

Answer 2

None of the listed firing control options, specifically, prevent thermal shock to a hot water boiler. Boilers incorporate design features to ensure gradual heating and minimize the risk of thermal shock (option d).

Step-by-step explanation:

The firing control that will prevent thermal shock to a hot water boiler is none of the options listed above. Thermal shock refers to the rapid temperature change that can occur within the boiler that can cause damage due to the different expansion rates of the boiler's materials. To prevent thermal shock, boilers are typically designed with features like gradual heating procedures, proper circulation, and temperature maintenance strategies, rather than relying on a specific control such as low limit, operating, or high limit control. These basic controls are primarily established for other safety and operational efficiencies instead of specifically addressing thermal shock prevention.

Hence, the answer is option d.