Venting — general information
3a
Chimney draft venting
Chimney draft venting uses the natural draft provided
by a vertical vent or chimney. Category I appliance (non-
positive vent static pressure and vent gas temperature
that avoids excessive condensate production in vent).
See Section
3b
. Chimney draft installations use:
1. Vent connector (single or doublewall) sized to
eliminate positive pressure in vent system. Diameter
increases immediately at boiler.
2. Doublewall metal vent (B-vent) or chimney with
liner approved by the National Fuel Gas Code,
ANSI Z223.1 – latest edition, or in Canada B149.1
or B149.2 Installation Code.
Direct exhaust venting
(vertical or sidewall)
Direct exhaust venting uses inside combustion air with
no combustion air connector piping. All CGt flue gas
vents are pressurized, requiring careful sealing of all
joints. Category III appliance (positive vent static pres-
sure and vent gas temperature that avoids excessive
condensate production in vent). See pages 15-19. Direct
exhaust installations use:
1. Vent pipe specified in this manual.
2. Vent termination through outside wall, roof or un-
used chimney. Tight chimney areas will make vent
joint construction very difficult.
Venting — chimney draft venting
3b
1. Use doublewall metal vent (B-vent) or chimney with liner as required by
the National Fuel Gas Code, ANSI Z223.1 – latest edition, or in Canada,
B149.1 or B149.2 Installation Code.
2. To prevent downdrafts, chimney should extend at least 3 feet above the
highest point where it passes through a roof and at least 2 feet higher
than any portion of a building within a horizontal distance of 10 feet.
3. To vent with another appliance, see National Fuel Gas Code, ANSI
Z223.1 – latest edition or in Canada B149.2 or B149.2 Installation Code.
4. Do not connect breeching to any portion of a mechanical draft system
that can operate under positive pressure.
5. Maintain minimum 2” clearance from combustible materials to vent
pipe.
6. Do not use chimney with an open fireplace.
7. Make horizontal runs as short as possible. Long runs can cause con-
densation.
8. When longer runs are used, support pipe with appropriate hangers.
9. To prevent blockage, do not vent into bottom of chimney.
10. Vent pipe must not go beyond inside wall of chimney.
11. Vent passing through floors or ceilings must be firestopped.
12. See
Figure 7
and
Table 2
to connect boiler to venting system.
Inspect existing chimney before installing boiler. Failure
to clean or replace perforated pipe or lining will cause
severe personal injury or death.
Vent sizing given in
Table 2
is only a general guideline.
The vent connector and chimney must be designed,
sized and constructed in compliance with all applicable
codes. Failure to correctly size and install the vent
system could result in severe personal injury, death or
substantial property damage.
CGt venting options — Chimney draft or Direct exhaust
14
Part Number
550-110-290/0219
CGt
GAS-FIRED WATER BOILER — Series 2 —
Boiler Manual
Boiler
model
number
“D” Minimum
vent connector
diameter
CGt
5”
Figure 7
Chimney draft
venting
Table 2
Vent connctor
diameter