What should happen if you suddenly lose the ID fan on a balanced draft boiler installation equipped with interlocks?

In a balanced draft boiler installation, both the forced draft (FD) fan and the induced draft (ID) fan are crucial for maintaining the necessary airflow and ensuring safe combustion. Since these systems work together to control the combustion air and flue gas removal, losing the ID fan creates a critical situation that can lead to unsafe conditions.

When the ID fan suddenly stops operating, the system's interlocks are designed to respond to this change in airflow. The interlocks are implemented as safety mechanisms that monitor the performance of both fans. The sudden loss of the ID fan disrupts the balance between the air coming into the boiler and the flue gases being exhausted. This imbalance can lead to a buildup of flue gases, which is hazardous.

As a safety measure, the system will trigger the interlocks to ensure that the forced draft fan is also shut off. This prevents fuel from continuing to be fed into the combustion area without adequate ventilation and exhaust capabilities. By shutting off the FD fan and the fuel feed, the boiler avoids conditions that could lead to incomplete combustion, which could result in dangerous situations such as explosions or carbon monoxide buildup.

Therefore, the decision to shut off both the FD fan and the fuel feed is a critical safety protocol designed to protect