Adjustment Procedures
5-14
750-96 (revised 2010)
Model CB Packaged Boiler Manual
THEN
4,184
= 3,546 CFH
1.18
This is the CFH (at line pressure) which must pass through the meter so that the equivalent full input requirement of
4,184 CFH (at base pressure) will be delivered.
Checking Gas Flow: Your gas supplier can generally furnish a gas meter flow chart from which gas flow can be
determined. After a short observation period, this information aids in adjusting the regulator to increase or
decrease flow as required to obtain rating.
Final adjustment of gas fuel is carried out by means of the adjusting screws in the gas modulating cam while per-
forming a combustion efficiency analysis. See Section 5.8 for details.
5.8 — Gas Fuel Combustion Adjustment
After operating for a sufficient period of time to assure a warm boiler, adjustments should be made to obtain effi-
cient combustion.
The appearance or color of the gas flame is not an indication of its efficiency since an efficient gas flame will vary
from transparent blue to translucent yellow.
Proper setting of the air/fuel ratios at all rates of firing must be established by the use of a combustion gas ana-
lyzer. This instrument measures the content, by percentage, of carbon dioxide (CO
2
), oxygen (O
2
), and carbon
monoxide (CO) in the flue gas.
Burner efficiency is measured by the amount or percentage of CO
2
present in the flue gas. The theoretical maxi-
mum CO
2
percentage for natural gas is approximately 11.7%. As shown in Figure 5-5, this is attained when there
is no excess oxygen (O
2
) or carbon monoxide (CO). A definite percentage of excess air (oxygen) is required by
most local authorities and the burner should never be operated with an air-fuel ratio that indicates a detectable
percentage of carbon monoxide.
Subject to local regulations pertaining to specific amounts of excess oxygen, it is generally recommended that
CO
2
readings of between 9-1/2% and 10-1/2% be attained with corresponding O
2
readings of 2% to 4%.
From information in Section 5.7 of this chapter, determine the standard condition of gas pressure and flow for the
size of the boiler and its gas train. Calculate the actual pressure and flow through the use of correction factors
that compensate for incoming gas pressure and altitude.
NOTE: The information given in this section is for all practical purposes sufficient to set and adjust controls for gas
input. Your gas supplier can, if necessary, furnish exact correction factors that take into consideration BTU content,
exact base pressure, specific gravity, temperature, etc., of the gas used.
Courtesy of: C3 Surplus LLC
Surplus Industrial Superstore
305-428-2777
https://www.c3surplus.com
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