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VII. Venting
D. Design Requirements Unique to Split Vent Systems (continued)
Table 7.21 summarizes all split vent options. Illustrations of split vent systems are shown in Figures 7.22, 7.23,
7.24a and 7.25a. In addition to the requirements in Section VII - A, observe the following design requirements:
1. Permitted Terminals for Split Venting:
Rigid Vent Systems (Vent Options 25-32) – Vent terminates in a plain end (coupling for PVC, bell end for PolyPro,
Polyflue, and plain end pipe for InnoFlue). Intake terminates in a PVC 90 sweep elbow pointing down. The
section of PolyPro, Polyflue or InnoFlue exposed to the outdoors must be UV resistant.
Use of a rodent screen is generally recommended for the vent termination. Two rodent screens are included
within the available 2" and 3" vent kits or can be fabricated from 1/2" stainless steel mesh screen. Rodent
screens are installed as shown in Figure 7.28. Rodent screens ("bird guards") for PolyPro, Polyflue and InnoFlue
are as follows:
Size/Vent System
2" PolyPro
3" PolyPro
2" Polyflue
3" Polyflue
2" InnoFlue
3" InnoFlue
Flex Vent Terminals (Options 33-39) – The flex vent kits shown for options 33-39 include vent terminals that must
be installed in accordance with the vent manufacturer's instructions. In some cases, different terminals are used
for Masonry and B-vent chimney chases.
Air Intake Terminals (Vent Options 25-39) - All split venting options shown in Tables 7.21 terminate in a PVC 90
sweep elbow pointing down. Use of rodent screens is generally recommended for both intake terminations. Two
rodent screens are included within the available 2" and 3" vent kits or can be fabricated from 1/2" stainless steel
mesh screen. Rodent screens are installed as shown in Figure 7.28.
2. Vent Terminal Location – Observe the following clearances from roof mounted vent terminals (also see Figures
7.22, 7.23, 7.24a or 7.25a):
•
Bottom of terminal must be at least 12" above the normal snow line anticipated on the roof.
•
Exhaust opening must be at least 2ft above any portion of the roof or structure located within horizontally
within 10ft.
3. Horizontal Air Intake Terminal Location - Observe the following limitations on the intake terminal location (also
see Figures 7.22, 7.23,7.24a, and 7.25a):
•
The bottom of all terminals must be at least 12" above the normal snow line. In no case should they be less
than 12" above grade level.
•
If possible, install the intake terminal on a wall away from the prevailing wind. Reliable operation of this boiler
cannot be guaranteed if the intake terminal is subjected to winds in excess of 40 mph.
•
Air intake terminal must not terminate in areas that might contain combustion air contaminates, such as near
swimming pools. See WARNING on page 13.
4. Use of abandoned chimneys as a Vent Chase for flexible Polypropylene Venting (Options 33-38) – Vent options
33-38 permit flexible Polypropylene venting to be routed to the roof using an abandoned masonry or B- vent
chimney. In these applications combustion air is drawn horizontally from a wall terminal. See Figure 7.23 or
7.24a. When using one of these vent options, observe the following requirements:
•
When a masonry chimney containing multiple flues is used as a chase, ALL flues must be abandoned
(Figure 7.24b).
•
Masonry or B vent chimney used as a chase must be structurally sound and in good repair.
•
Use of flex Polypropylene outside of a masonry or B-vent chimney is not permitted unless allowed by the
vent manufacturer and permitted by local codes.
•
All venting is Polypropylene supplied by the vent manufacturer shown in Table 7.21. The portion of this
venting within the masonry or B–vent chimney is flexible.
•
All flex pipe must be installed vertically. Up to two offsets (four bends) may be made in the vertical run of flex
pipe. Bends used to make these offsets may not exceed 45 degrees (Figure 7.24b).
•
Because the flex pipe is corrugated, it has a higher pressure drop than the rigid pipe used elsewhere in the
vent system. Equivalent lengths for flex venting are shown in Table 7.14. Reduce the maximum allowable
vent length shown in Table 7.21 by this equivalent length for each foot of flex pipe used, as well as for each
elbow in addition to the first. The first elbow and termination are not counted. If offsets (described above)
are present, the equivalent length of the bends in these offsets can also be ignored.
34
D. Design Requirements Unique to Split Vent Systems
Rodent Screen ("Bird Guard")
DuraVent # 2PPS-BG
DuraVent # 3PPS-BG
Selkirk #2PF-HVST
Selkirk #3PF-HVST
Centrotherm # IASPP02
Centrotherm # IASPP03
107672-03 - 5/18
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