Form 433-CV/LN, Page 6
Figure 5B - Typical Common Vent Application of a unit
heater and a water heater venting into a Tile-lined
Masonry Chimney
11. Venting (cont'd)
11B. Requirements and Instructions for Common Venting (Refer to Figures 5A and 5B and
Common Vent Tables 1-4) (cont'd)
n
Vent Connector Rise (cont'd)
Tile-lined
Masonry
Chimney
R1
H
4", Type B
Double-Wall
Vent Connector -
Maximum
horizontal length
is 6 ft (1.8M)
Water
Heater
Key to Figures 5A and 5B AND/OR Tables (pages 7-10)
H (appears in illustrations and tables) = Common Vent Height
Definition - The common vent height is the vertical distance
measurement from the highest drafthood outlet or flue collar
to the vent cap or chimney outlet of the common vent.
R (appears in tables only) = Vent Connector Rise
Definition - The vent connector rise is the vertical
distance measurement from each heater or appliance
outlet to the centerline where the vent gas streams come
together.
R1 (appears in illustrations only) = Vent Connector Rise (R
above) of the Category I Appliance in Figures 5A and
5B IMPORTANT: Be certain that the appliance being
vented with the heater is one that is permissible for common
Category I venting.
R2 (appears in illustrations only) = Vent Connector Rise (R
above) of Model FT30-CV, FT45-CV, or FT45-LN in
Figures 5A and 5B (NOTE: In Figure 5B, there is no
R2 because the vent connector rise is zero.)
Type B
Double-Wall
Common Vent
4" Type B Double-Wall
Vent Connector -
Maximum horizontal
length is 6 ft (1.8M)
Vent
Connector
of another
Category I
appliance
H
R1
R2
Category I Appliance
(water heater)
Model FT
-CV or -LN
Model FT
-CV or -LN
Maximum Length of the Vent Connector of Other Category I
Appliance
Connector Diameter
Maximum Horizontal Length
3"
4-1/2 ft (1.4M)
4"
6 ft (1.8M)
5"
7-1/2 ft (2.3M)
6"
9 ft (2.7M)
7"
10-1/2 ft (3.2M)
8"
12 ft (3.7M)
9"
13-1/2 ft (4.1M)
10"
15 ft (4.6M)
n
Common Vent
Definition - The vertical portion of a Type B double-wall vent or
tile-lined masonry chimney into which two or more vent connec-
tors attach
n
Common Vent Height
Definition - Vertical distance measurement from the highest draft-
hood outlet or flue collar to the vent cap or chimney outlet of the
common vent (See Figures 5A and 5B).
Add the BTUH's of the appliances and use the Common Vent Ca-
pacity Tables to determine permissible common vent size and height
combination. If either of the connector vents in the system are single-
wall vent pipe, use a single-wall vent pipe table.
Model FT-CV or FT-LN Common Vent Height Requirements
NOTE: Because Model FT-CV and -LN is fan assisted, the col-
umn Nat/Nat does not apply. Depending on the other appli-
ance, use either Fan+Nat or Fan+Fan.
Type B Double-Wall Pipe - Depending on the type of vent con-
nector, use Table 1B or Table 2B
Masonry Chimney lined with Type B or a Listed Liner (see note
under table) - Depending on the type of vent connector, use Table
1B or Table 2B
Interior Tile-lined Masonry Chimney - Depending on the type
of vent connector, use Table 3B or Table 4B
Figure 5A - Typical
Common Vent
Application of a unit
heater and a water
heater using a Type
B Double-Wall
Common Vent
