Commissioning
4-22
750-382
CBT
4.1.17 — Low and high fire adjustments
All CBT boilers are factory tested firing natural gas at an altitude of 1000
ft ASL. Operating under different conditions may require re-adjustment of
the gas valve.
Adjustments are made using a TORX® T40 (low fire adjustment) and 3
mm hex wrench (main gas choke). The adjustment screws should initially
be set to half way through each setting’s range. The low fire adjustment
screw is accessed by removing the slotted cap on the gas regulator using
a blade screwdriver (see Figure 4-12). The high fire adjustment screw is
accessed by removing the blue plastic cap from the valve cover (see
Figure 4-13).
Turn the adjustment screw completely clockwise, counting the turns until
the screw will no longer turn. Then, turn the adjustment screw
counterclockwise half the number of turns counted when turning
clockwise.
NOTE:When adjusting low fire offset, clockwise adjustments increase gas flow, and counterclockwise
adjustments decrease gas flow.
When adjusting the main gas choke, clockwise adjustments decrease gas flow, and counterclockwise
adjustments increase gas flow.
Refer to Appendix A for further information on gas valve setup, operation, and
testing.
4.1.18 — Modulation OFF point
Prior to setting combustion, the steam pressure off hysteresis point should be
adjusted upward to avoid nuisance shutdowns while the burner is under
manual control. This parameter is located under Steam Configuration.
NOTE: Install the combustion analyzer probe as close as possible to the boiler
vent connection. Sampling too far from the boiler vent can produce false
readings due to air leakage diluting the flue gas.
4.1.19 — Setting Combustion
Note: A Combustion Analyzer is required to properly set-up the Model CBT burner. Do not attempt to fire and
adjust the burner without this equipment.
Note: Ensure boiler is filled with water prior to burner startup.
The burner does not have need of linkages for fuel/air adjustment, nor is a separate manual-auto switch
provided for burner positioning. All firing rate adjustments are accomplished via the CB Falcon Control. Setting
combustion will require manually modulating the burner via the CB Falcon from low fire to high fire to ensure
a consistent air/fuel ratio.
To enable the burner, go to the Operation screen and press the <Burner switch> button at the upper left. The
burner will not operate if this button is in the “OFF” state.
FIGURE 4-16. Regulating adjusting
screw - low fire offset
FIGURE 4-17. Main gas choke -
high fire adjustment
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