CleaverBrooks CBLE, Руководство по эксплуатации и обслуживанию

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Adjustment Procedures
6-6 750-91 (revised 2009)
Model CB-LE Packaged Boiler Manual
Separate and independent controls affect modulated firing and burner on-off cycling.
FIGURE 6-4.
Firing Graph
The burner will be “on” whenever the pressure or temperature is less than point B (see Figure 6-4) and “off ”
whenever pressure or temperature is greater than point A . The distance between points A and B represents the
“on-off ” differential of the operating limit control.
In normal operation, the burner will shut down whenever the pressure or temperature rises above setting A . At that
point the switch in the operating limit control will open. As the pressure or temperature drops back to B , the oper-
ating limit control closes and the burner will restart. The modulating control will signal the modulating motor to be
in a low-fire position. If the load demands exceed the low fire input potential, the modulating control will increase
the firing rate proportionately as pressure or temperature falls toward point
D . The modulating motor will stop at
any intermediate point between C and D whenever the fuel input balances the load requirement.
As the load requirement changes, the firing rate will change accordingly. Thus it is referred to as modulated firing.
Point D represents the maximum firing rate of the burner, or high-fire. In the event pressure or temperature drops
while the burner is firing at high-fire, it indicates that the load exceeds the capacity of the boiler.
The firing graph (Figure 6-4) shows that point B and point C do not coincide. Extreme load conditions could
require the points be closely matched.