For automatically fired hot water heating boilers rated at 400,000 BTU or less, when is a low water cut off device required?

A low water cut-off device is essential for safety in automatically fired hot water heating boilers rated at 400,000 BTU or less, especially when any part of the circulation system is situated below the level of the boiler. This requirement is in place because if the water level drops below the boiler, the heating elements can continue to operate, leading to overheating, potential damage to the boiler, and even a risk of explosion if the system is not properly monitored.

By having the low water cut-off device installed, it ensures that the boiler will shut down automatically if the water level drops dangerously low, regardless of the operating conditions. This safeguard is crucial because it helps prevent hazardous situations that could arise from inadequate water levels, thus maintaining the integrity and safety of the heating system.

Other criteria mentioned, such as whether the system is filled with water, the pressure exceeding 50 psi, or continuous operation, do not inherently trigger the need for a low water cut-off device since the safety risk primarily arises when there's a potential for low water conditions.