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FORCED DRAFT OIL FIRED BOILERS
BOILER SERIES
DRAFT AT
BOILER
OUTLET (i.w.c.)
CO
2
@
HIGH FIRE
O
2
@
HIGH FIRE
CO
(ppm)
SMOKE
NO.
D -0.01 TO -0.04 10.0 TO 12.0 % 4.0 TO 7.2 % < 400 0
CL 0.0 TO -0.04 10.0 TO 12.0 % 4.0 TO 7.2 % < 400 0
RV & RW +0.50 TO -0.10 11.5 TO 12.5 % 3.7 TO 5.0 % < 400 0
AB +0.25 TO -0.06 11.5 TO 12.5 % 3.7 TO 5.0 % < 400 0
NOTE: THE VALUES FOR CO
2
AND O
2
ARE SHOWN FOR HIGH FIRE ONLY. THE VALUES FOR LOW
FIRE OR MID RANGE WILL GENERALLY BE LOWER, PARTICULARLY FOR ATMOSPHERIC GAS-
FIRED BOILERS. DRAFT SHOULD BE MEASURED APPROXIMATELY 24" FROM TOP OF BOILER,
BEFORE ANY DRAFT CONTROL.
2.5.1 DRAFT ADJUSTMENT - ATMOSPHERIC
GAS BOILERS
Refer to Section 1.8.6 for the adjustment method
for barometric dampers. Adjust the damper so as
to yield a draft which results in values of CO
2
and
CO within the allowable limits listed above in the
appropriate table.
Draft adjustments are generally not required for
boilers equipped with draft diverters. The diverter
must be installed without modification.
Combustion readings are required, however, to
assure that the boiler operation is both safe and
efficient.
Draft measurement should preferably be made
with an inclined tube manometer. If a draft gauge
is not available, check to be sure the flue gases
are being carried up the venting system by
passing a lighted taper or match around the edge
of the draft hood relief opening (or barometric). If
the venting system is operating correctly, the
match flame will be drawn toward the draft hood
relief opening. Otherwise the products of
combustion will tend to push the flame and
extinguish it.
CAUTION
IF THE PRODUCTS OF COMBUSTION ARE
BEING EMITTED INTO THE ROOM (VENTING
SYSTEM NOT OPERATING CORRECTLY),
THE BOILER MUST NOT BE OPERATED
UNTIL PROPER ADJUSTMENTS OR REPAIRS
ARE MADE TO ASSURE ADEQUATE DRAFT
THROUGH THE VENTING SYSTEM.
2.5.2 DRAFT ADJUSTMENT -FORCED DRAFT
BOILERS
Draft adjustments are generally not necessary on
forced draft boilers. The draft must be measured
as part of the start-up procedure. The measured
draft at the boiler flue should fall within the
recommended range specified in the appropriate
table.
On some installations the draft may be excessive
due to a high chimney. In these cases, the draft
should be adjusted within the recommended
range specified in the above appropriate table.
This may be done using a barometric damper, a
restrictor, or a locking quadrant damper. Such
devices must be installed and adjusted by a
qualified technician.
2.5.3 COMBUSTION ADJUSTMENTS -
FORCED DRAFT
Refer to the separate burner manual for the
procedures for burner adjustments. The burner
must be adjusted for smooth lightoff. Combustion
parameters should be within the range specified
in the above appropriate table. In no case should
the level of CO be allowed to exceed the limit
given, and the smoke spot reading must also not
exceed the value shown.