Finned copper tube gas boilers & water heaters – Boiler Manual
10
Chimney Inspection & Sizing – Category I and II
A thorough inspection of the masonry chimney must be performed to
ensure that the chimney is clean, properly constructed, lined and sized.
Exterior masonry chimneys should not be used unless properly lined
to prevent condensation and draft problems. Tables 5 & 6 list the
equivalent breeching and flue sizes required for the boiler/water heater.
Correctly identify the type of vent system the appliance
requires before proceeding. Category identification is
noted on the unit rating label.
Table 5 Equivalent Breeching & Chimney Size, Negative Pressure
(Category I)
Model Size
Pipe Diameter
in
mm
500
–
–
750
8
203
1000
10
254
1250
10
254
1500
10
254
1750
12
305
2000
12
305
Note: These sizes are based on a
20 ft, 6.1m chimney height.
Figure 6
Vertical Venting with a Metal Chimney System
(Category I)
Figure 7
Vertical Venting with a Metal Chimney System
(Category II)
Vent Connections
Locate the boiler/water heater as close to the chimney 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 a
single wall stainless steel vent pipe the same diameter as the flue
collar to connect the boiler/water heater to a masonry chimney.
When using a listed metal chimney system use the appropriate vent
connector.
The vent connector should be sloped up toward the chimney at a
minimum rate of
1/4 in/ft
,
21 mm/m
. On masonry chimneys
the connector must terminate flush with the inside of the chimney
flue, Figures 8 & 9. Fasten each single wall vent connection with at
least 3 corrosion resistant sheet metal screws.
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
Model Size
Pipe Diameter
in
mm
500
6
152
750
6
152
1000
7
178
1250
8
203
1500
8
203
1750
10
254
2000
10
254
Note: These sizes are based on a
20 ft, 6.1m chimney height.
Table 6 Equivalent Breeching & Chimney Size, Negative Pressure
(Category II)
