FIGURE 7
GENERAL INFORMA
GENERAL INFORMA
GENERAL INFORMA
GENERAL INFORMA
GENERAL INFORMATION
TION
TION
TION
TION
GAS VENTS AND APPLIANCES
GAS VENTS AND APPLIANCES
GAS VENTS AND APPLIANCES
GAS VENTS AND APPLIANCES
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), or low flue gas temperatures
(Category II). Category III and IV appliances are fan forced vents with high temperature
(Category III) or 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 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.
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WARNING:
ARNING:
ARNING:
ARNING:
ARNING:
Vents for Category I appliances may not be suitable for use with
Category II, III, or IV appliances because condensate may corrode the vent.
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WARNING:
ARNING:
ARNING:
ARNING:
ARNING:
Vents for Category III appliances may not be suitable for use
with Category I appliances because flue gas temperatures may be too high.
Proper operation of the vent system and appliance is dependent upon the use of all parts
specified by the manufacturer for use in the particular installation. Appliance and vent
system performance may be affected by improper assembly.
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