Cleaver-Brooks CBH 40 - Page 58

Chapter 5--Adjustment and Maintenance
scale lock down and turn the scale clockwise
approximately 70° (motor stroke is 75°).
Release the scale lock.
e) Turn cam until the cam roller of the switch
lever is exactly over the outer corner of the
operational cam lobe. Slight movement of the
cam at this point should produce an audible
click in the switch. Tighten the operational
cam's locking screw.
f) No cam differential is desired between the
make and the break of the contacts, so be sure
that the differential cam lobe (brass colored)
and the operational cam lobe are aligned so
that the differential cam has no effect on the
switch.
g) Tighten thumb screw.
h) Mount the switch on the motor. Connect the
red and blue leads to the oil valve circuit
(HFOV) or to the high fire switch (HFS) as
shown on your boiler wiring diagram. The
yellow lead is not required and its end should
be insulated to prevent short circuits.
i) Check
out the operation of the switch under
actual operating conditions. Readjust the cam
SCALEPLATE
(BLACK SCALE)
DIFFERENTIAL CAM
LOCKING SCREW
CAM
ROLLER -----:
SWITCH
if necessary to assure oil valve opening and
closing at the desired point. If the switch is
used for proving that the air damper reaches
high fire position during pre-purge, the setting
is not critical and it should make between
two-thirds and full motor travel.
HIGH FIRE SWITCH -
CBH 25 THRU 40 AND 50A
When insurance requirements call for a high fire
switch on the 25 thru 40 and 50A sizes, a Q607B
switch (two micro-switches) is attached to the
damper motor.
The first switch is used for the high fire oil valve
circuit. The second switch is used to prove that the
air damper is open during pre-purge.
The following directions are based on adjusting
the switch prior to its attachment to the damper.
While particularly useful during replacement, they
also serve as a guide for final adjustment.
a) BEFORE attaching switch to the mounting
bracket, depress the scale lock and rotate the
scale so that the zero mark on the black scale
is close to the index mark as shown in Figure
5-7.
INDEX
MARK
OPERATING CAM
(SILVER)
DIFFERENTIAL
CAM (BRASS)
THUMBNUT
SCALE
LOCK
FIGURE 5-6. Q607A AUXILIARY SWITCH (SINGLE MICRO-SWITCH)
5-16