23
Category III or IV Installation of Vent/Air Piping
SECTION III - CATEGORY III OR IV INSTAL-
LATION OF VENT/AIR PIPING
A Category III or IV appliance utilizes uncontaminated
indoor or outdoor air (surrounding the appliance) for com-
bustion.
Category III or IV - Vertical - Thru the Roof or An
Unused Chimney
Installation of the vent and combustion air piping
must comply with local codes and requirements and
with the National Fuel Gas Code NFPA 54, ANSI
Z223.1 for installations in the U.S. or CSA B149.1 or
B149.2 for installations in Canada.
When using an unused chimney as a means of a
raceway for the vent, the surrounding space
within the chimney cannot be used to draw com-
bustion air or vent another appliance,
A gas vent extending through a roof should not
terminate near an adjacent wall or below any
building extensions such as roof eaves, balconies
or decks. Failure to comply with the required
clearances could result in severe personal injury,
death or substantial property damage.
WARNING
NOTICE
NOTICE
Determine Termination Location
Locate the vent and combustion air termination using the
following guidelines:
1.
The total length of the vent must not exceed the limits
given in Table 3 on page 30.
Do not include the rain cap used to terminate the
vent when determining the total length of pipe.
2. The combustion air piping must terminate at the
appliance with a 90
º
elbow.
3. The vent must terminate vertically with a rain cap
and must be located 12 inches above the roof or
projected snowline as shown in Fig. 14.
NOTICE
Refer to Vent
Manufacturer's
Recommended
Clearances
Refer to Vent Manufacturer's
Recommended Clearances
000
To Drain
According to
Local Codes
Combustion
Air Inlet
Condensate
Drain with
Trap Loop
Storm
Collar
Rain Cap
Adjustable
Flashing
Roof Jack
Firestop
Support
Clamp
2 Ft.
Max.
12” Min. Above
Grade or Projected
Snow Line
Vertical- Single Pipe
Fig. 14:
