750-96 (revised 2010)
Model CB Packaged Boiler Manual
1-15
1.12 — Combustion Air
1.12 — Combustion Air
Air for combustion of fuel (often referred to as “secondary” air) is furnished by the forced draft fan mounted in the
boiler head. In operation, air pressure is built up in the entire head and is forced through a diffuser plate for a
thorough mixture with the fuel for proper combustion. The supply of secondary air to the burner is governed by
automatically throttling the output of the fan by regulating the rotary air damper. This furnishes the proper
amount of air for correct ratio of air to fuel for efficient combustion at all firing rates.
FIGURE 1-6. Secondary Air Flow
1.13 — Automatic Ignition
Oil or gas burners are ignited by an interrupted type pilot. The pilot flame is ignited automatically by an electric
spark.
A series 100 burner usually is equipped with a pilot fired with light oil fuel. All other burners, as well as a series
100 burner complying with insurance underwriters requirements, are equipped with a gas burning pilot. In the
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