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Cast Iron Condensing Boilers – Installation Manual
FlexCore Stainless Steel Condensing Boilers – Installation Manual
DIRECT VENT
POSITIVE PRESSURE, CATEGORY IV
In this configuration the boiler blower is used to push
the flue products to the outdoors while drawing
combustion air from the outdoors. The INTAKE AIR
OPTION instructions under the COMBUSTION AIR &
VENTILATION SECTION must be followed!
Horizontal Direct Vent Systems - Figures 2 & 3
The vent materials used in positive pressure vent
systems must be certified to UL 1738 for installations in
the United States, ULC S636 for installations in Canada.
To maximize the performance of single wall sheet metal
vent systems locate 90° elbows as far from the boiler as
possible and from one another. For best results, horizontal
vent systems should be as short and straight as possible.
The vent system must be both gas and water tight.
All seams and joints in metal pipes must be joined and
sealed in accordance with the vent system manufacturer’s
instructions.
Use (Table 4) for the maximum Category (IV) equivalent vent length and the equivalent length per fitting.
Table 4 - “Category IV Equivalent Length per Fitting” chart is meant as a guideline for preliminary sizing. If
vent length approaches 75% of maximum length listed, an engineered vent system calculation must be
performed. Consult factory.
Table 4 - Category IV Maximum Equivalent Vent Length & Equivalent Length per Fitting
The RBI Flexcore is supplied with a factory installed DuraVent FastNSeal flue outlet adapter. A
manufacturers supplied stainless steel transition piece must be used when installed with different vent
systems. Do not mix vent systems of different manufacturers. Use only listed manufacturers (Table X),
terminations (Table Y), and transition adapters (Table Z). The chimney systems manufacturer's installation
instructions must be followed.
Model/Outlet
Diameter
K*
0850 1000 1500 2000 2500 3000 3500 4000 4500 5000 6000 7000 8000 9000
5"
5"
6" 6" 8"
8"
10"
10"
10"
12"
12"
14"
14"
14"
Maximum Equivalent
Length (Catagory IV)
100' 100' 100' 100' 100' 100' 100' 100' 100' 100' 100' 100' 100' 100'
Standard Tee
1.25 20 ft 25 ft 25 ft 30 ft 35 ft 35 ft 40 ft 40 ft 40 ft 50 ft 50 ft 55 ft 55 ft 55 ft
Boot Tee
0.65 10 ft 15 ft 15 ft 15 ft 15 ft 15 ft 20 ft 20 ft 20 ft 25 ft 25 ft 30 ft 30 ft 30 ft
Cap - Low Res (UL)
0.50 10 ft 10 ft 10 ft 15 ft 15 ft 15 ft 15 ft 15 ft 15 ft 20 ft 20 ft 25 ft 25 ft 25 ft
45° w/Bird Screen
0.40 7 ft 10 ft 10 ft 10 ft 10 ft 10 ft 15 ft 15 ft 15 ft 15 ft 15 ft 15 ft 15 ft 15 ft
Elbow - 90°
0.38 10 ft 10 ft 10 ft 10 ft 10 ft 10 ft 15 ft 15 ft 15 ft 15 ft 15 ft 20 ft 20 ft 20 ft
Elbow - 45°
0.15 5 ft
5 ft
5 ft
5 ft
5 ft
5 ft
7 ft
7 ft
7 ft
7 ft
7 ft
7 ft
7 ft
7 ft
*Equivalent lengths based on K factors and (5X) pipe diameters straight length between fittings.
When horizontal vent runs exceed
5 ft, 1.5m they must
be supported at
3 ft, 0.98 m intervals with overhead
hangers. If any part of a single wall metal vent system
passes through an unheated space it must be insulated
with insulation rated for
400°F, 212°C.
Horizontal vent systems shall terminate at least
4 ft,
1.3 m below,
4 ft, 1.3 m horizontally from or 1 ft,
0.23 m above any door, window or gravity air inlet into any
building. It must not terminate less than
4 ft, 1.3 m
horizontally from, and in no case above or below, unless
a
4 ft, 1.3 m horizontal distance is maintained, from electric
meters, gas meters, regulators and relief equipment and
not less than
7 ft, 2.3 m above adjacent public walkway.
The bottom of the vent terminal(s) shall be located at least
5 ft, 1.5 m above the air intake terminal(s) unless there is
a
5 ft, 1.5 m distance between them.
4)
Vertical Vent (individual venting only) (page 14)
- Negative Pressure, Category II uses stainless
steel vent system certified to UL 1738 for
installations in the United States, and a stainless
steel vent system certified to ULC S636 for
installation in Canada. Combustion air is obtained
from the space in which the unit is installed.
5)
Common Vent (page 10) - Negative Pressure,
Category II uses a stainless steel vent system
certified to UL 1738 for installations in the United
States, and a stainless steel vent system certified to
ULC S636 for installations in Canada.
