Cleaver-Brooks CBH 40 - Gas Burner

the flue gas. Efficiency is measured by the per-
centage of C02 present in the flue gas. The ideal
setting from a standpoint of efficiency is reached
when there is no measurable percentage of oxygen
present. It is, however, more practical to set the
burner to operate with a reasonable amount of ex-
cess air to compensate for minor variations in the
pressure or burning properties of oil. 15 to 20 per-
cent excess air is considered normal. A C02 range
of 12 to 13% is desirable. The burner should never
be operated with an air-fuel ratio that indicates a
detectable percentage of carbon monoxide.
Turn the burner to high fire and let it operate at
this rate for several minutes. Observe the color and
size ot the flame. Color alone is a poor means of
determining efficiency, although it can serve as a
guide for tentative setting. If smoke or haze is
visible additional combustion air is required. If the
flame is overly bright, rumbles or emits sparks the
amount of combustion air will have to be reduced.
Determine that the proper atomizing oil pressure
exists as mentioned in the preceding section cover-
ing nozzles. In some instances, conditions may
require that the oil pressure be reduced below the
suggested setting if a desired flue gas analysis can
not be obtained with an open damper.
Take a sample of flue gas with an instrument
known to be in good working order and determine
COz reading. Based on this analysis, make any
required adjustments to increase or decrease air
flow. See the section on air damper adjustment in
this chapter.
Recheck low fire to determine whether it was af-
fected by high fire adjustments. If so, additional
linkage adjustment may be required.
G. GAS BURNER
GENERAL
There are relatively few adjustments that can be
made to the burner drawer, however, a check
should be made to see that all components are
properly located and that all holding devices such
as setscrews are properly tightened. Periodically
inspect the burner drawer for evidence of damage
due to improperly adjusted combustion.
Check the gas pilot electrode for proper setting (see
figure 5-4)
and also for any cracks in the porcelain
insulator. Cracks can cause grounding of ignition
voltage. Check the tip of electrode for signs of pit-
ting and dress as required. Check the ignition cable
for insulation cracks. See that all connections be-
tween transformer and electrode are tight.
GAS PILOT FLAME ADJUSTMENT
The size of the gas pilot flame is regulated by ad-
justing the gas flow through the pilot gas regulator.
The flame must be sufficient to ignite the main
flame and to be seen by the flame detector but an
Chapter 5-Adjustment and Maintenance
extremely large flame is not required. An overly
rich flame can cause sooting of the flame detector.
Too small a flame can cause ignition problems.
To check the pilot flame, visually observe it thru
the rear sight port. A flame that encircles approxi-
mately one-half of the diffuser is satisfactory. To
control the flame size, make the necessary adjust-
ment to the gas pilot regulator.
A preferred method of setting a flame is to obtain a
micro-amp reading of the flame signal. This can be
measured with a good quality micro-ammeter or a
suitable multi-meter with a zero to 25 micro amp
DC rating.
The meter is connected to a jack in the amplifier of
the flame safeguard control. Use a meter connect-
ing plug harness (Cleaver-Brooks 884-72). Connect
the plus (red meter lead) to the red tab of the har-
ness and the minus (black meter lead) to the black
tab before inserting the plug in the meter jack.
( 1) To measure and adjust the pilot, turn the
damper switch to low. Fully open the pilot
shut-off cock. Close the cock in the main gas
line.
(2)
Connect the micro-ammeter as outlined
above.
(3) Turn burner switch on. Let the burner go
through the normal pre-purge cycle. When
the ignition area of the timer dial is op-
posite the index notch, set the timer switch
to the TEST position to stop the timer.
Relay 2K should pull in when the pilot
ignites.
( 4)
If the pilot flame is not established within
ten seconds, turn off the burner switch.
Repeat the lighting attempt.
NOTE: On an initial starting attempt, portions of
the fuel lines may be empty and require
"bleeding" time. It is better to accomplish
this with repeated short lighting trial
periods with intervening purge periods
than to risk prolonged fuel introduction. If
the pilot does not light after several at-
tempts, check all components of the pilot
system.
(5) When the pilot flame is established, remove
the flame detector from the burner plate.
The pilot flame can then be observed thru
this opening.
CAUTION: Keep eyes sufficiently away from the
sight tube opening and wear a pro-
tective shield or suitable glasses.
Never remove the flame detector
while the main burner is firing.
(6) To make the final adjustment, slowly close
the gas pilot regulator until the flame can
no longer be seen through the sight tube.
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