A: Standard atmospheric boilers have combustion
systems that require both primary air and secondary air
for operation. The primary air is introduced through the
air shutters and mixed with the gas from the gas
orifices. The rich gas/air mixture is then introduced into
the combustion chamber through the burners and is
ignited by an ignitor of some type (standing pilot,
interrupted pilot or hot surface ignitor, HSI). Upon
ignition, the flame has an insufficient supply of air
(primary air) provided with the gas and obtains the
additional air (secondary air) required for proper
combustion from the area immediately adjacent to the
flame. The primary and secondary air are draft induced
by a chimney or in the case of side wall vented boilers
by a draft inducer or power venter.
Download
