When should a Low Water Cut Off (LWCO) be active?

A Low Water Cut Off (LWCO) is designed to monitor the water level within a boiler and is a critical safety device. The correct situation for the LWCO to be active is when the water level in the boiler is approximately 1/2 to 3/4 inches above the Low Steam Water Level (LSWL).

This is important because the LSWL is the minimum water level required to ensure safe operation of the boiler. If the water level drops below this threshold, there is a risk of overheating and damage to the boiler's components, which could lead to catastrophic failures. Therefore, the LWCO should be active to prevent the boiler from operating under unsafe conditions by cutting off the burner or heating elements when the water level is close to this critical point.

In contrast, the other options do not correctly describe the right conditions for the operation of the LWCO. For instance, water dropping below atmospheric pressure does not directly relate to the functionality of an LWCO, nor does reaching a maximum temperature or exceeding pressure limits pertain to the primary concern of maintaining a safe water level. Thus, the emphasis on maintaining the water level above the LSWL aligns with the safety role of the LWCO.