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Section 2 - STACK AND INTAKE VENTING
2.1 - Venting Connections - General
2.1.1 - Appliance Categories
Proper installation of flue gas exhaust venting is critical for the efficient and safe operation of the CFC-
E boiler. The boiler’s appliance category is a major factor determining venting system design.
Definitions:
Boilers are divided into four categories based on the pressure and temperature produced in the exhaust
stack and the likelihood of condensate production in the vent.
• Category I. A boiler which operates with a non-positive vent static pressure and with a vent gas temperature that avoids
excessive condensate production in the vent.
• Category II. A boiler which operates with a non-positive vent static pressure and with a vent gas temperature that may cause
excessive condensate production in the vent.
• Category III. A boiler which operates with a positive vent pressure and with a vent gas temperature that avoids excessive
condensate production in the vent.
• Category IV. A boiler which operates with a positive vent pressure and with a vent gas temperature that may cause excessive
condensate production in the vent.
Depending on the application, the Model CFC-E may be considered Category II, III, or IV. The
specifying engineer should dictate flue venting as appropriate to the installation.
Notice
For additional information on boiler categorization, see appropriate ANSI Z21 Standard and
the latest edition Standard of National Fuel Gas Code or in Canada, the latest edition of CSA
Standard B149 Installation Code for Gas Burning Appliances and Equipment, or applicable
provisions of local building codes.
!
Warning
Contact the manufacturer of the vent material if there is any question about the boiler categorization
and suitability of a vent material for application on a Category II, III or IV vent system. Using improper
venting materials can result in property damage, personal injury, or death.
Notice
A vent cap is not recommended for condensing applications. Condensate can freeze on the
vent cap, resulting in a blocked flue. See below for more information.
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