750-91 (revised 2009)
Model CB-LE Packaged Boiler Manual
6-25
6.22 — Burner Drawer Adjustment
6.21.1 — Standard Burner Low-Fire Adjustment: Heavy Oil
The fuel input should be adjusted with the low-fire cam screw, to approximately 25% of that at high-fire. At low
fire the O
2
flue gas reading should be between 7% and 8%.
6.21.2 — High Turndown Burner Low-Fire Adjustment: Light Oil
Fuel input at low-fire should be approximately 12.5% of that at high-fire. The low-fire screw should be adjusted to
obtain the necessary input for the fuel turndown required. At low-fire the O
2
flue gas reading should be between
7% and 9%. The second cam adjusting screw may need to be adjusted in order to maintain a smooth cam profile.
6.22 — Burner Drawer Adjustment
There are relatively few adjustments that can be made to the burner; however, a check should be made to assure
that all components are properly located, and that all holding screws are properly tightened.
The diffuser location on gas fired boilers is quite important. There should be 1/4” distance between the edges of
the diffuser fins and gas outlet tubes (spuds) (see Figure 6-16). The setting of an oil fired burner is less exacting and
the diffuser should be located with the skirt approximately 1-1/8” from the end of the burner tube.
FIGURE 6-16. Standard Burner
When the proper diffuser location is ascertained, the setting of the nozzle in relation to the diffuser should be
checked. This generally is set at time of manufacture and seldom needs altering. It is most important that oil spray
does not impinge upon the diffuser. The distance that the nozzle is behind the diffuser has some latitude, and indi-
vidual installations may require a slight deviation. The spacing indicated is 2”.
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