Chapter 6 Adjustment Procedures
6-2 750-177
2. Initial adjustment should be made with the motor in full
closed position, that is with the shaft on the power end of
the motor in its most counterclockwise position.
3. The closer the linkage rod connector is to the drive shaft,
the less the arm will travel; the closer the connector is to
the driven shaft, the farther that arm will travel.
Figure 6-1 shows the linkage required for a gas-oil
combination burner. Prior to initially firing a boiler it is
advisable to check for free movement of the linkage. The
damper motor must be allowed to complete its full stroke and
the damper must move freely from low to high fire position.
Adjustment of linkage connected to a gas butterfly valve is
described in Section P of Chapter 6.
C. MODULATING MOTOR
The modulating motor has a 90° shaft rotation. The motor
manufacturer also provides a 160° stroke model for other
applications.
If a replacement is obtained from someone other
than a Cleaver-Brooks Service or Parts representative, it may
have an incorrect stroke. To prevent damage, verify the 90°
stroke prior to installing a replacement.
The stroke may be determined by powering the motor and
connecting terminals R-B to actually determine the stroke as
motor drives to an open position.
D. MODULATING MOTOR SWITCHES
- LOW FIRE AND HIGH FIRE
The modulating motor contains either one or two internal
switches depending upon application. The microswitches are
actuated by adjustable cams attached to the motor shaft.
Factory replacement motors have the cams preset. The low
fire start switch is set to make the red and yellow leads at
approximately 8° on motor closing. The high fire purge air
proving switch (located in 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 Service Technician. 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.
Figure 6-1: Complete Linkage Assembly -
Combination Gas and Oil
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