CleaverBrooks FLX 1000, Руководство по эксплуатации, обслуживанию и запасным частям

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Adjustment Procedures Chapter 5
750-177 5-5
To properly set the modulating control, carefully adjust it under load conditions, until the load is maintained
with the burner firing at a steady rate. The firing rate at that point may be full high fire or slightly less,
depending upon the relationship of the boiler size to the load.
When the modulating control is set and the burner is in full high fire, the scale setting of the modulating
pressure control on a steam boiler will indicate the low point of the modulating range. The scale setting of the
modulating temperature control on a hot water boiler will have a reading that indicates the midpoint of the
modulating range.
The operating limit control should now be adjusted and the differential established. In an installation that does
not require a very close control of steam pressure or water temperature the adjustable differential (Figure 5-3
A to B) should be set as wide as conditions permit, since a wide setting will provide less frequent burner
cycling.
The high limit control provides a safety factor to shut the burner off in the event the operating limit control
should fail. The setting of the control should be sufficiently above the operating limit control to avoid nuisance
shutdowns. The setting, however, must be within the limits of the safety valve settings and should not exceed
90% of the valve setting. The control requires manual resetting after it shuts off the burner.
In the setting of the controls, consideration must be given to the time required for a burner restart. Each start,
requires a prepurge period, plus the fixed time required for proving the pilot and main flame. In addition,
approximately one-half minute is required for the damper motor to travel from low to high fire. The time lag
may allow pressure or temperature to drop below desirable limits.
F. MODULATING PRESSURE CONTROL
(Steam)
Figure 5-2: Steam Controls
Turn the adjusting screw until the indicator is opposite
the low point of the desired modulating range.
Modulated firing will range between the low point and a
higher point equal to the modulating range of the
particular control. In 0-15 psi controls the range is 1/2
psi.
! DANGER CAUTION
To prevent burner shutdown at other than low-fire
setting, adjust the modulating pressure control to
modulate to low fire BEFORE the operating limit
pressure control shuts off the burner. Failure to fol-
low these instructions could result in damage to
the equipment
G. OPERATING LIMIT PRESSURE CONTROL (Steam)
Set the “cut-out” (burner-off) pressure on the main scale using the large adjusting screw. Set the differential
on the short scale by turning the small adjusting screw until the indicator points to the desired difference
between cut-out and cut-in pressures. The “cut-in” (burner-on) pressure is the cut-out pressure MINUS the
differential. The cut-out pressure should not exceed 90% of the safety valve setting.
H. HIGH LIMIT PRESSURE CONTROL (Steam)
Set “cut-out” (burner off) pressure on the main scale using the adjusting screw. The control will break a circuit
when pressure reaches this point. The setting should be sufficiently above the operating limit pressure control
to avoid shutdowns, and preferably not exceed 90% of safety valve setting. The control requires manual
resetting after tripping on a pressure increase. To reset, allow pressure to return to normal and then press the
reset button.