What should be the minimum air flow during the pre-purge of a gas or oil fired boiler?

The minimum air flow during the pre-purge of a gas or oil fired boiler is essential for ensuring safe and efficient operation. The correct choice indicates that a minimum of 25% full-load air flow is necessary during the pre-purge phase. This level of air flow is designed to effectively clear any combustible gases from the combustion chamber before ignition occurs.

Pre-purge is a critical safety step to prevent potential explosions or harmful emissions that could arise if residual fuel or gas was left in the combustion area. By utilizing 25% of the full-load air flow, the system adequately dilutes any lingering gases and ensures that the chamber is prepared for the ignition process in a controlled manner.

This requirement is based on industry standards and guidelines, which emphasize the importance of maintaining a specific air flow rate to enhance the efficiency of the combustion process while also ensuring safety protocols are firmly in place. While higher percentages of air flow may provide additional safety, the minimum requirement is set to balance both safety and operational efficiency without being unnecessarily excessive.