12
APPLICABLE FEDERAL CODES
VENT SYSTEM MODIFICATION
When an existing boiler is removed from a common venting
system, the common venting system is likely to be too large
for the proper venting of the appliances remained connected
to it. If this situation occurs, the following test procedure must
be followed:
REMOVAL OF BOILER FROM VENTING SYSTEM
At the time of removal of an existing boiler, the following steps
shall be followed with each appliance remaining connected
to the common venting system placed in operation, while the
other appliances remaining connected to the common venting
system are not in operation.
Seal an unused opening in the common venting system.
1.
Visually inspect the venting system for proper size and
2.
horizontal pitch and determine there is no blockage or re
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striction, leakage, corrosion and other deficiencies which
could cause an unsafe condition.
Insofar as is practical, close all building doors and win-
3.
dows and all doors between the space in which the
appliances remaining connected to the common venting
system are located and other spaces of the building. Turn
on clothes dryers and any other appliance not connected
to the common venting system. Turn on any exhaust fans,
such as range hoods and bathroom exhausts, so they
operate at maximum speed. Do not operate a summer
exhaust fan. Close fireplace dampers.
Place in operation the appliance being inspected. Follow
4.
the lighting instructions. Adjust thermostat so appliance
will operate continuously.
Test for spillage at the draft hood relief opening after 5
5.
minutes of main burner operation. Use the flame of a
match or candle, or smoke from a cigarette, cigar or pipe.
After it has been determined that each appliance remain
-
6.
ing connected to a common venting system properly
vents when tested as outlined above, return doors, win-
dows, exhaust fans, fireplace dampers and any other gas
burning appliances to their previous condition of use.
Any improper operation of the common venting system
7.
should be corrected so the installation conforms with
the latest revision of the National Fuel Gas Code, ANSI
Z223.1. When resizing any portion of the common venting
system, the common venting system should be resized to
approach the minimum size as determined using the ap
-
propriate tables in the latest revision of the National Fuel
Gas Code, ANSI Z223.1.
NFPA 54/ANSI Z223.1, National Fuel Gas Code and NFPA/
ANSI 211, Chimneys, Fireplaces, Vents and Solid Fuel Burning
Appliances. These codes contain information on special gas
vents for Category II, III and IV appliances, vent sizing, location,
air space clearances to combustibles and safe installation
practices. The gas vent installer should be familiar with these
Federal Codes as well as Local Codes and Regulations.
GENERAL INFORMATION GAS VENTS AND
APPLIANCES:
By Federal Codes, gas appliances are categorized by the
pressure and temperature of the flue gas vented from the
appliance. Category I and II appliances are natural draft (draft
hood) vented, with high flue gas temperatures (Category I), and
low flue gas temperatures (Category II). Category III and IV
appliances are fan forced vents with high temperature (Category
III) and low temperature (Category IV) flue gasses. Appliance
efficiency is directly related to flue gas temperature. Higher
efficiency appliances remove more heat from the gas, so they
Vents for Category I appliances may not be suitable
for use with Category II, III, or IV appliances because
condensate may corrode the vent.
WARNING
!
Vents for Category III appliances may not be suitable
for use with Category I appliances because flue gas
temperatures may be too high.
WARNING
!
will have lower temperature flue products. When flue gas
temperatures are lowered, corrosive condensates may form
in the gas vent or in the appliance. Condensates may form
in Category II, III, IV appliance vents, so special, corrosive
resistant venting systems are required for higher efficiency
appliances.