John Wood Atmospheric Gas (Standard) - Manual (Page 14)

14
Do not terminate the vent connector in a chimney that has not
been certified for this purpose. Some local codes may prohibit
the termination of vent connectors in a masonry chimney.
Vertical Exhaust Gas Vent
Vertical exhaust gas vents must be installed with certified
(listed) type B vent pipe according to the vent manufacturer’s
instructions and the terms of its listing.
It must be connected to the water heater’s draft hood by
a certified vent connector or by directly originating at the
draft hood opening.
Vertical gas vents must terminate with a certified cap or
other roof assembly and be installed according to their
manufacturer’s instructions.
Gas vents must be supported to prevent damage, joint
separation, and maintain clearances to combustible
surfaces (Figures 9 and 10).
IMPORTANT: This gas vent must be terminated in a
vertical position to facilitate the removal of the burnt gases.
An unused chimney flue or masonry enclosure may be used
as a passageway for the installation of a gas vent (Figure 10).
Common (combined) venting is allowable with vertical type
B vent systems and lined masonry chimneys as long as
proper draft for the water heater is established under all
conditions of operation. CAUTION: DO NOT common vent
this water heater with any power vented appliance.
Figures 8-10 are examples of vent pipe system
VENTING THROUGH A CHIMNEY WITH
TYPE B DOUBLE WALL VENT PIPE.
LISTED VENT CAP
VENT CONNECTOR
UNUSED CHIMNEY
FLUE OR MASONRY
ENCLOSURE
SEAL
MAINTAIN
CLEARANCE
VENT
CONNECTOR
SLOPE UP
1/4 IN. PER FT.
(21 mm
PER METRE)
MINIMUM
MAINTAIN
SPECIFIED
CLEARANCE
SUPPORT
STRAP
MAINTAIN SPECIFIED CLEARANCE
1,2
1
1
FIGURE 10.
VERTICAL GAS VENT SYSTEM WITH
TYPE B DOUBLE WALL VENT PIPE.
LISTED VENT CAP
TYPE B DOUBLE
WALL VENT PIPE
MAINTAIN
SPECIFIED
CLEARANCE
VENT
CONNECTOR
SLOPE UP
1/4 IN. PER FT.
(21 mm PER METRE)
MINIMUM
MAINTAIN
CLEARANCE
SUPPORT
STRAP
MAINTAIN SPECIFIED CLEARANCE MAINTAIN
SPECIFIED
CLEARANCE
1,2
1
1
1
FIGURE 9.
1 Vent pipe must be installed according to CAN/CSA B149.1-current edition (Natural Gas and Propane
Installation Code) and all local/provincial codes.
2 Refer to local building code and/or the National Building Code of Canada.
installations and may or may not be typical for your
specific application. Consult the “Natural Gas and Propane
Installation Code,” CAN/CSA B149.1-current edition and
the guidelines set forth by prevailing local codes.
Vent Size Verification
It is possible that the existing venting system was sized
through a common vent for a previous installation. Such
an arrangement is appropriate for venting two appliances
(such as the original water heater and a standard vent
furnace). If this is true and the second appliance has been
removed from the existing venting system (such as when
the furnace has been upgraded to a power vent type), the
venting system is now supplying only one appliance. This
condition is commonly referred to as “orphaning.” In such
cases, the venting system must be properly resized
for a single appliance.
Therefore, it is important to verify the size of the existing
venting system. Improper sizing can cause a number
of undesirable and potentially unsafe results including
spillage of the products of combustion into the room, poor
combustion, excessive condensation, pilot outage, or
delayed ignition. The vent pipe must not be obstructed so
as to prevent the removal of exhaust gases to the outside
atmosphere.