When are two low water cut-offs required on a steam heating boiler?

Two low water cut-offs are required on a steam heating boiler specifically when the boiler has pumped condensate returns and an input over 200,000 BTU. This requirement is rooted in safety regulations and the operational needs of larger steam boilers.

When a steam heating boiler exceeds 200,000 BTU, it operates at a higher risk level for low water conditions, which can lead to overheating and boiler damage. The presence of pumped condensate returns further complicates the situation because it can create scenarios where the water level rapidly fluctuates. To mitigate the risks associated with these conditions, having two low water cut-offs provides an added layer of safety. One acts as a primary safeguard, while the second serves as a backup, ensuring that if one fails or becomes inaccurate, the other can still prevent the boiler from operating under unsafe low water conditions.

The other options do not warrant the need for dual low water cut-offs either because they fall under different categories of boiler operation or because they do not provide the same level of risk as those with over 200,000 BTU capacity combined with pumped condensate systems. For instance, smaller boilers may not pose the same risk, and altitude or steam traps do not inherently require dual cut-offs.