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Cast Iron Condensing Boilers – Installation Manual
FlexCore Stainless Steel Condensing Boilers – Installation Manual
Figure 8 - Vertical Venting with a Metal Chimney System
Vent Connections
Locate the boiler as close to the chimney system as
possible. Use the shortest, straightest vent connector
possible for the installation. If horizontal runs exceed
5 ft, 1.5 m they must be supported at 3 ft, 0.9 m
intervals with overhead hangers. Use the appropriate
vent connector of the same diameter as the flue collar
to connect the boiler to a listed metal chimney system.
Follow the chimney system manufacturer’s instructions
for proper assembly.
The vent system should be sloped up toward the
chimney at a minimum rate of
1/4 in/ft, 2 cm/m.
Always provide a minimum clearance of
6 in, 152 mm
between single wall vent pipe and any combustible
materials.
Failure to maintain minimum clearances
between vent connectors and any
combustible material can result in a fire
causing extensive property damage, severe
personal injury or death!
Exit cones are favorable when used
to increase the velocity of the flue
gas exiting the stack and, may also
help, in cold climates, to reduce ice
build-up. Exit cone terminations must
be supplied by others, installed per
manufacturer’s instructions, and meet
local and federal code.
generic exit cone
VERTICAL VENT (Optional)
NEGATIVE PRESSURE - CATEGORY II
The FlexCore is listed as a Category II appliance when
vented vertically into a UL 1738 listed stainless steel
chimney system, Figure 8. The chimney system must
provide a negative pressure of
0.02 to 0.10 in, 0.51 to
2.5 mm WC at the boiler flue collar with the unit running.
When using a listed metal chimney system
the chimney system manufacturer ’s
instructions must be followed.
Multiple boiler vent systems must be
designed and verified by a qualified
professional and stack manufacturer. The
vent system must prevent backflow of
exhaust gas through idle boilers.
When more than one appliance is connected to the same
chimney system the system must be large enough to
safely vent the combined output of all of the appliances.
Table 5 lists the equivalent breeching and chimney
sizes required for a single boiler installation.
If an appliance using any type of a
mechanical draft system operating under
positive pressure is connected to a chimney
flue, never connect any other appliances to
this flue. Doing so can result in excessive
levels of carbon monoxide which can cause
severe personal injury or death!
Table 5 - Equivalent Breeching & Chimney Size,
Negative Pressure - Single Boiler
These sizes are based on a
20 ft, 6.1m
chimney height.
2 FT .6 m ABOVE
THE HIGHEST POINT
WITHIN 10 FT 3.1 m
CAP
STORM COLLAR
ROOF FLASHING
CLEARANCES PER VENT
MANUFACTURER'S INSTRUCTIONS
OFFSET ONLY IF
NECESSARY
FRAMING MEMBERS
BETWEEN JOISTS
JOIST
INSULATION
CLEARANCES
PER VENT
MANUFACTURER'S
INSTRUCTIONS
RIOM-0208_B
FIRESTOP
Model
Size
Breech & Flue Diameter
in
mm
0850
8
204
1000
8
204
1500
8
204
2000
10
254
2500
12
305
3000
12
305
3500
12
305
4000
12
305
4500
14
356
5000
14
356
6000
14
356
7000
16
406
8000
16
406
9000
16
406
Note:
1) All building
structural
modifications
by others.
2) Firestopping
per local
building codes.
