Chapter 6 — Adjustment Procedures
Part No. 750-184 6-5
the modulating motor) is set to make red and blue tracer leads at
approximately 60° the on motor opening. Normally the settings are
left as is, but job conditions may require readjustment. If the cams
require adjustment or resetting, follow the instructions in the
manufacturer’s technical manual.
E. BURNER OPERATING CONTROLS - GENERAL
Note: Adjustments to the boiler operating controls should be
made by an authorized Cleaver-Brooks Representative.
Refer to the appropriate boiler Operation and
Maintenance manual for specific information on boiler
startup and operation.
The standard boiler operating control package consists of three
separate controls, the High Limit Control
, Operating Limit Control
and the Modulating control.
The High Limit Control
senses the hot water temperature or steam
pressure. It is used as a safety limit to turn the burner off in the
event the operating limit control fails. The high limit control should
be set sufficiently above the operating limit control to avoid
nuisance shutdowns.
The Operating Limit Control
senses temperature or pressure and
automatically turns the burner on to initiate the start up sequence
when required and turns the burner off to initiate the shutdown
sequence when the demand is satisfied. The control must be set to
initiate startup only at the low fire position.
The Modulating Control
senses changes in the hot water
temperature or steam pressure and signals the modulating motor to
control the flow of fuel and air to the burner. With either steam or
hot water boilers, the modulating control must be set to ensure the
burner is at its minimum low fire position before the operating limit
control either starts or stops the burner.
When adjusting or setting controls, first be sure all control devices
are securely mounted and level. With the temperature sensing
control, make sure the sensing bulb is properly bottomed in its well
and is secured against movement. Be sure the connecting tubing is
not kinked.
The dial settings are generally accurate, although it is not unusual
to have a slight variation between a scale setting and an actual
pressure gauge or thermometer reading. Always adjust control
setting to agree with pressure gauge or thermometer readings.
Accurate instrument readings are required. When necessary use
auxiliary test equipment to set controls.
Burner controls correctly set to match load demands will provide
operational advantages and achieve the following desirable
objectives:
• The burner will be operating in low fire position prior to shut
down.
• The burner will operate at low fire for a brief period on each start
during normal operation.
Figure 6-4 Steam Operating Controls
Figure 6-5 Hot Water Controls
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