Bryan Boilers Forced Draft Steam Boilers ユーザーズマニュアル

 

 

 

 

 

 

 

 

 

 

 

 

 

Ventilation Air: In addition to air needed for 
combustion, sufficient air must be supplied for 
ventilation, including air required for comfort and 
proper working conditions for personnel in the 
boiler room. In colder climates, provision should 
also be made to heat the boiler room, if 
necessary, for personnel comfort. 
                                                                  

Protection from combustion air contamination: 
Where corrosive or flammable process fumes are 
present in the vicinity of the boiler room or the air 
stream for the combustion air supply, it is 
essential that suitable means be provided for their 
safe  

disposal. The boiler room and the combustion air 
supply must not be exposed to the fumes. Such 
fumes include, but are not limited to, carbon 
monoxide, hydrogen sulfide, ammonia, chlorine, 
and halogenated hydrocarbons. 
 
NOTE: Halogenated hydrocarbons are 
particularly injurious and corrosive after exposure 
to high temperatures. 
                                                                  

 

 

 
CODE COMPLIANCE 
The installation must conform to the requirements 
of NFPA 54, the National Gas Code  (ANSI 
Z223.1-1984), Part 7, "Venting of Equipment", or 
to the applicable requirements of all local building 
codes. For factory-built and listed chimney 
systems (such as type B vent), consult the 
system manufacturer's instructions for correct 
installation procedures. Gas vents may be of any 
of the construction types listed in this manual. No 
portion of a venting system may extend into or 
pass through any circulating air duct or plenum. 
 
MINIMUM SAFE PERFORMANCE 
Venting systems must be designed to develop 
positive flow adequate to remove flue gases to 
the outside atmosphere. Guidelines are provided 
in this manual and in the National Fuel Gas Code, 
NFPA 54, for sizing and design of flue gas 
venting systems. For additional reference to good 
practice in vent design, refer to the "Chimney, 
Gas Vent, and Fireplace Design" chapter of the 
ASHRAE Equipment Handbook. 
 
OUTSIDE VENTS AND CHIMNEYS 
Outside uninsulated single wall pipe is not 
recommended for use in cold climates for venting 
gas-fired appliances since temperature 
differentials may cause corrosion in such pipe, as 
well as poor draft on start ups. When local 
experience indicates that condensate may be a 
problem, provisions should be made to drain off 
the condensate in the gas vent or chimney. 

ESTIMATING FLUE GAS FLOW RATE (ACFM) 
Flue gas volumetric flow rate in SCFM (standard 
cubic feet per minute) and ACFM (actual cubic 
feet per minute) can be estimated by using the 
information in 1.8.1A.  Divide the Total Input of 
appliances connected to the chimney or vent by 
1000. Then multiply this result times the factor 
listed in the SCFM and ACFM table. The ACFM 
data is required for determining stack exit velocity 
and induced draft fan requirements. 
 
ESTIMATING STACK EXIT VELOCITY 
First, determine the ACFM for the stack as 
described above. Multiply the total ACFM times 
the Velocity Factor from the Velocity Table in 
Table 1.8.1B for the stack diameter used. The 
result is the Stack Exit Velocity in feet per second. 
 
ESTIMATING STACK EMISSIONS 
Table 1.8.1C lists approximate emissions of NOx 
(oxides of nitrogen) and CO (carbon monoxide). 
The table lists both the concentration, in parts per 
million (ppm),  and the flow rate, in pounds per 
hour (PPH), of each compound: Divide the total 
input of appliances connected to the chimney or 
vent by 1,000,000. Then multiply this result times 
the value listed in the table for PPH emissions. 
 
MANUAL REFERENCES 
See Figure 1.8.1 for a graphics listing of 
applicable sections of this manual for each 
section of the vent system.