A low water cut off device on an automatically fired hot water heating boiler rated at 350,000 BTUH is required when:

The correct answer regarding the requirement for a low water cut-off device on an automatically fired hot water heating boiler rated at 350,000 BTUH is that any portion of the circulating system is located below the boiler.

In hot water heating systems, a low water cut-off device serves a critical safety function. It prevents the boiler from operating if the water level drops below a certain point, which can happen if there are leaks in the system, or if the system is not being properly maintained. If any part of the circulating system is positioned below the boiler, there is a risk that the boiler could potentially become empty of water due to gravity draining, which can lead to overheating and damage to the boiler components. Hence, installation of a low water cut-off device becomes essential to ensure that the boiler will shut down safely under these conditions.

The other scenarios presented do not specifically necessitate the use of a low water cut-off device based on the fundamental operational principles and safety guidelines outlined for boiler systems. For example, the presence or absence of external ductwork or maintenance activities do not directly influence such a critical safety requirement in the same way that the relative position of system components does. The main focus is ensuring proper water level management across the heating system to prevent