RBI Gas boilers - Direct Vent System Configurations; Horizontal Direct Vent Systems; Vertical Direct Vent Systems; Combination Direct Vent Systems

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Table 4 Category IV Equivalent Length Per Fitting
Model/Outlet
Diameter
*K
Equivalent Feet of Straight Pipe
CB500
7"
CB750
7"
CB1000
7"
CB1250
8"
CB1500
8"
CB1750
10"
CB2000
10"
Standard Tee 1.25 25 ft 25 ft 30 ft 30 ft 35 ft 40 ft 40 ft
Boot Tee 0.65 15 ft 15 ft 15 ft 15 ft 15 ft 20 ft 20 ft
Cap - Low Res (UL) 0.50 10 ft 10 ft 10 ft 10 ft 10 ft 15 ft 15 ft
45° w/Bird Screen 0.40 10 ft 10 ft 10 ft 10 ft 10 ft 10 ft 10 ft
Elbow - 90° 0.38 10 ft 10 ft 10 ft 10 ft 10 ft 15 ft 15 ft
Elbow - 45° 0.15 5 ft 5 ft 5 ft 5 ft 5 ft 5 ft 40 ft
*Equivalent lengths based on listed K-factors and (5x) pipe diameters straight length between  ttings.
Must consult factory when venting single or multiple unit(s)
over 60 equivalent feet. Mechanical system may be required.
DIRECT VENT, POSITIVE PRESSURE,
CATEGORY IV
In this con guration the boiler/water heater blower is used to push
the  ue products to the outdoors while drawing combustion air
from the outdoors.  e Intake Air Option instructions under the
“COMBUSTION AIR & VENTILATION” section must be
followed!  e vent system must be sized per Table 5.
Table 5 Category IV
Model
Size
Pipe Diameter (Min.)
(Up to 60 ft)
in mm
500 7 178
750 7 178
1000 7 178
1250 8 203
1500 8 203
1750 10 254
2000 10 254
Horizontal Direct Vent Systems
Figures 1 & 2
 e vent materials used in horizontal vent systems must be certi ed
to UL 1738 for installations in the United States, ULC S636 for
installations in Canada.  e certi ed vent terminal from RBI must
also be used.
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,
204°C. Structural penetrations must be made using approved  re-
stops. For best results, horizontal vent systems should be as short
and straight as possible.
 e vent system must be both gas tight and watertight. All seams
and joints in metal pipes must be joined and sealed in accordance
with the vent system manufacturer’s instructions.
When horizontal vent runs exceed 5  , 1.5 m they must be supported
at 3  , 0.9 m intervals with overhead hangers.  e vent system must
be pitched down, toward the vent terminal, 1/4 in/ , 20 mm/m. 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, 204°C.
Horizontal vent systems shall terminate at least 4  , 1.2 m below,
4  , 1.2 m horizontally from or 1  , 0.30 m above any door, window
or gravity air inlet into any building. It must not terminate less than
4  , 1.2 m horizontally from, and in no case above or below, unless
a 4  , 1.2 m horizontal distance is maintained, from electric meters,
gas meters, regulators and relief equipment and not less than 7  ,
2.1 m above adjacent public walkway.  e bo om of the vent
terminal(s) shall be located at least 5  , 1.5 m above the air intake
terminal(s) unless there is a minimum 5  , 1.5 m horizontal
separation between them. Avoid terminal locations likely to be
a ected by winds, snowdri s, people and pets. Protect building
materials and vegetation from degradation caused by the  ue gases.
Vertical Direct Vent Systems – Figure 3
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, 204°C.
Structural penetrations must be made using approved  re-stops.
An approved, nonrestrictive vent terminal must be used.  e top
of a vertical vent system must extend at least 5
1
/
2
 , 1.7 m above
the roof surface and maximum snow line that it passes through,
4  , 1.2 m above the intake air terminal, see Figure 3.
In addition the vent system must conform to the dimensions shown
in Figure 3.  e penetration point in the roof must be properly
 ashed and sealed.
 e vent system must be gas tight. All seams and joints in metal
pipes must be joined and sealed in accordance with the vent system
manufacturer’s instructions.
Combination Direct Vent Systems – Figure 4
 e boiler/water heater can be vented vertically with the intake
air piped horizontally through an outside wall. Follow the instruc-
tions in the Intake Air Option – Horizontal Guidelines on page
5. Also follow the general instructions in the “COMBUSTION
AIR & VENTILATION” and “GENE L VENTING GUIDE
LINES” sections.