Where should a low water cutoff (LWCO) be installed on a heating boiler?

The low water cutoff (LWCO) should be installed 2 inches below the normal operating water level (NOWL) to ensure that it is able to effectively monitor the water level in the boiler. By positioning the LWCO below the NOWL, it acts as a safety device that can detect when the water level drops below a safe operating point, thus preventing potential damage to the boiler caused by low water conditions.

This installation strategy is crucial because if the water level drops too low, it could lead to overheating and failure of the boiler components. The LWCO will trigger an alarm or shut off the burner, providing a critical fail-safe mechanism that protects both the equipment and the overall system integrity.

The other options do not provide optimal locations for the installation of the LWCO. For instance, placing it at the waterline may not allow for early detection of low water conditions. Installing it above the NOWL would risk missing low water situations, while a location at the bottom of the boiler may not accurately indicate water levels that affect safe operation.