750-392
CBEX-DE
3-17
Linkage Settings (optional single-point systems)
The low fire setting should be regarded as tentative until the proper gas pressure for high-fire operation is estab-
lished. To reach high-fire rate:
1. Turn the manual flame control switch toward “OPEN” in minor increments while monitoring combustion for
overly rich or lean conditions.
2. At high-fire the gas butterfly valve should be open as wide as indicated by the slot on the end of the shaft. Set
and lock the high-fire stop screw so that it is just touching the valve arm.
3. Determine the actual gas flow from a meter reading.
4. With the butterfly valve open and with regulated gas pressure set at the calculated pressure, the actual flow
rate should be close to the required input. If corrections are necessary, increase or decrease the gas pressure
by adjusting the gas pressure regulator, following the manufacturer’s directions for regulator adjustment.
When proper gas flow is obtained, take a flue gas reading. The O2 should be between 3% and 4% at high-fire.
If the fuel input is correct, but the O2 values do not fall within this range, the air damper travel may need to be
adjusted.
With the high-fire air/fuel ratio established, the gas pressure regulator needs no further adjusting.
After being certain that the air control damper and its linkage are correctly adjusted to provide the proper amount
of air, and after adjusting the gas pressure regulator, final adjustment can be made, if necessary, to the gas mod-
ulating cam to obtain a constant air/fuel ratio throughout the entire firing range.
Since the input of combustion air is ordinarily fixed at any given point in the modulating cycle, the flue gas read-
ing is determined by varying the input of gas fuel at that setting. The adjustment is made to the metering cam by
means of adjusting screws, which are turned outward (counterclockwise from the hex-socket end) to increase the
flow of fuel, and inward (clockwise from the hex-socket end) to decrease it. Flow rate is highest when the cam
follower assembly is closest to the jackshaft.
To Next Page
Loading...
Need help?
General
