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5 Vertical direct venting (continued)
Vent/air termination – vertical
Prepare roof penetrations
1. Air pipe penetration:
a. Cut a hole for the air pipe. Size the air pipe hole as
close as desired to the air pipe outside diameter.
2. Vent pipe penetration:
a. Cut a hole for the vent pipe. For either combustible
or noncombustible construction, size the vent pipe
hole with at least a 1/2 inch clearance around the
vent pipe outer diameter:
• 5½ inch hole (140 mm) hole for 4 inch (102 mm)
vent pipe
• 7½ inch hole (191 mm) hole for 6 inch (152 mm)
vent pipe
b. Insert a galvanized metal thimble in the vent pipe
hole (when required by local codes).
3. Space the air and vent holes to provide the minimum
spacing shown in FIG.’s 5-1A and 5-1B, page 30.
4. Follow all local codes for isolation of vent pipe when
passing through fl oors, ceilings, and roofs.
5. Provide fl ashing and sealing boots sized for the vent pipe
and air pipe.
Termination and fi ttings
1. Prepare the vent termination coupling and the air
termination elbow (FIG.’s 5-1A and 5-1B) by inserting
bird screens. Bird screens should be obtained locally.
2. The air piping must terminate in a down-turned 180°
return bend as shown in FIG.’s 5-1A and 5-1B. Locate the
air inlet pipe no further than 2 feet (.6 m) from the center
of the vent pipe. This placement avoids recirculation of
fl ue products into the combustion air stream.
3. The vent piping must terminate in an up-turned coupling
as shown in FIG. 5-1A. The top of the coupling must be
at least 1 foot (.3 m) above the air intake. When the vent
termination uses a rain cap as illustrated in FIG. 5-1B
maintain at least 36" (914 mm) above the air inlet. The
air inlet pipe and vent pipe can be located in any desired
position on the roof, but must always be no further than
2 feet (.6 m) apart and with the vent termination at least
1 foot (.3 m) above the air intake.
4. Maintain the required dimensions of the fi nished
termination piping as shown in FIG.’s 5-1A and 5-1B.
5. Do not extend exposed vent pipe outside of building
more than shown in this document. Condensate could
freeze and block vent pipe.
Multiple vent/air terminations
1. When terminating multiple Knight XL boilers, terminate
each vent/air connection as described in this manual
(FIG. 5-2).
Terminate all vent pipes at the same height
and all air pipes at the same height to
avoid recirculation of fl ue products and
the possibility of severe personal injury,
death, or substantial property damage.
2. Place roof penetrations to obtain minimum clearance
of 12 inches (305 mm) between edge of air intake
elbow and adjacent vent pipe of another boiler for U.S.
installations (see FIG. 5-2). For Canadian installations,
provide clearances required by CSA B149.1 Installation
Code.
3. The air inlet of a Knight XL boiler is part of a direct vent
connection. It is not classifi ed as a forced air intake with
regard to spacing from adjacent boiler vents.
12" (305 MM) MINIMUM
VERTICALLY FROM VENT
OUTLET TO ANY AIR INLET
12" (305 MM) MINIMUM FROM EDGE
OF AIR INTAKE PIPE TO ADJACENT
VENT PIPE FROM ANOTHER BOILE
R
AIR
AIR
VENT
VENT
Figure 5-2 Vertical Terminations with Multiple Boilers
VENT
VENT
AIR
AIR
12" (305 MM) MINIMUM
VERTICALLY FROM VENT
OUTLET TO ANY AIR INLET
Figure 5-3 Alternate Vertical Terminations with Multiple
Boilers
ƽ WARNING
Installation & Operation Manual