Adjustment Procedures
6-20
750-91 (revised 2009)
Model CB-LE Packaged Boiler Manual
FIGURE 6-13. Fuel Modulating Cam
Through the manual flame control switch, position the cam so that the adjusting screw adjacent to the end or high-
fire screw contacts the cam follower. Perform a combustion analysis at this point. If an adjustment is necessary,
turn the adjustment screw accordingly to increase or decrease fuel flow. Take a combustion reading to verify input.
Repeat as necessary until the desired flow is obtained. Repeat the process, stopping at each adjusting screw, until
the low-fire adjusting screw is reached.
6.17.1 — Standard Burner Low-Fire Adjustment
The fuel input should be adjusted using the low-fire cam screw, to approximately 25% of that at high-fire (see Fig-
ure 6-8). At low-fire the O
2
flue gas reading should be between 6% and 7%.
It may be necessary to readjust the setting of the low-fire stopscrew to obtain the proper air/fuel ratio at the low-
fire rate. To ensure that the low-fire position of the gas butterfly valve is always the same, allow one turn of the stop
screw for overtravel.
If the air damper needs to be adjusted in order to provide the correct low-fire air/fuel ratio, combustion must be
rechecked at higher firing rates and adjusted as required.
If all cam screws are properly adjusted, none will deviate from the general overall contour of the cam face.
NOTE: Do not use any lubricant on the adjusting setscrews. The setscrews have a nylon locking insert intended to
provide locking torque and resistance to loosening and a lubricant could damage the equipment.
To Next Page
Loading...
Need help?
General
