Cleaver-Brooks CBH 40 - High Gas Pressure Switch; Programming Control; Control Operational Test

control consideration must be given to the fact that
gas line distribution pressure may decrease under
some conditions and it is advisable that the control
does not cut out unnecessarily.
The switch must be manually reset after tripping
on a drop of gas pressure below the cut-out setting.
To reset allow gas pressure to rise and press the
manual reset button.
HIGH GAS PRESSURE SWITCH
Turn adjusting screw until indicator on scale
moves to a pressure setting slightly above the
maximum operating gas pressure. The control will
break a circuit if pressure exceeds this value. The
control should be adjusted to prevent operation
with excessive gas pressure but should not be set at
a value close enough to normal operating pressure
to cause unnecessary shutdowns.
This switch must be manually reset after tripping
on a rise of gas pressure above the cut-out setting.
To reset allow gas pressure to drop and press the
manual reset button.
LOW OIL PRESSURE SWITCH
(Optional)
This control prevents burner from igniting or stops
its operation when the oil pressure drops below a
set point. The control contains a single-pole,
single-throw mercury switch which closes on a
pressure rise. Pressure settings are made with the
knobs on the face of the control. The "low" setting
indicates the point at which switch action takes
place on a pressure drop. Initially set this knob to
the bottom of the scale. Adjust the "high" knob to
a point slightly below the normal operating oil
pressure. Then set "low" knob somewhat lower.
The burner will operate as long as oil pressure ex-
ceeds the lower setting.
PROGRAMMING CONTROL
This control requires no adjustment, nor should
any attempt be made to alter contact settings. The
contacts may require occasional cleaning. If so,
follow
instructions given in the manufacturer's
bulletin. Do not use abrasive materials. The con-
trol cabinet door should be closed during normal
operation.
The manufacturer's bulletin also contains trouble-
shooting information.
The flame detector lens should be cleaned as often
as operating conditions demand. Use a soft cloth
moistened with detergent if necessary.
Replacement of internal components, other than
the plug in amplifier is neither practical nor
recommended.
When replacing a control or cleaning contacts, be
Chapter 5-Adiustment and Maintenance
sure to open the main power supply switch, since
the control is "hot" even though the burner switch
is off.
A
periodic safety check procedure should be
established to test the complete safeguard system
at least once a month or oftener. Tests should
verify safety shut down and a safety lock out upon
failure to ignite the pilot, upon failure to ignite the
main flame, and upon loss of flame. Each of these
conditions should be checked on a scheduled basis.
These tests will also verify fuel valve tightness.
Checking Pilot flame failure
Close the gas pilot shutoff cock. Also shut off the
main fuel supply. Turn the burner switch "on''.
The pilot system will be energized at the end of the
prepurge period. Since there is no pilot flame to be
detected, the pilot valve will be de-energized and
the main fuel valves will not be energized. Check
to see that there is an ignition spark but no flame.
The programmer will complete its cycle during
which time the lockout switch will trip on a safety
lock out.
Turn the burner switch off. Reset the safety switch
after allowing the thermal element to cool for a
few
moments. Reopen the gas pilot shut off cock
and re-establish main fuel supply.
Checking failure to lighl Main Flame
Leave the gas pilot shut off cock open. Shut off the
main burner fuel supply. Turn the burner switch
on. The pilot will light upon completion of the pre-
purge period. The main fuel valve(s) will be
energized but there should be no flame. Relay 2K
should drop out within 4 seconds after main bur-
ner ignition trial ends. The safety switch should
trip and lock out about 30 seconds after end of the
ignition trial.
Turn the burner switch off. Reset the safety switch
after allowing the thermal element to cool for a
few
moments. Re-establish the main fuel supply.
Checking Loss of Flame
With the burner in normal operation, shut off the
main burner fuel supply to extinguish main flame.
Relay 2K should drop out within 4 seconds after
flame is extinguished. The blower motor runs
during the post purge. The lock out switch will trip
approximately 30 seconds later de-energizing
master relay lK.
Turn the burner switch off. Reset the safety switch
after allowing the thermal element to cool for a
few
moments. Re-establish main fuel supply.
CONTROL OPERATIONAL TEST
Proper operation of the various controls should be
verified and tested when the boiler is initially
placed into service or whenever a control is
replaced. Periodic checks should be made there-
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