5-565.1
7
additional requirements for Horizontally vented
category iii units
1. Seal the joints with a metallic tape or silastic suitable for
temperatures up to 350°F. (3M tapes 433 or 363 are
acceptable.) Wrap tape two full turns around the vent pipe.
2. Refer to Table 7.2 for total minimum and maximum vent
lengths making the vent system as straight as possible.
The equivalent length of a 90° elbow is 5 feet for 4" diameter
and 7 feet for 6" diameter.
3. The vent terminal must be a Gary Steel 1092.
4. The vent must extend a minimum of 12" beyond the exterior
wall surface as shown in Figure 7.2. The vent must be
supported as shown in Figure 7.3. Precautions must be taken
to prevent degradation of building materials by flue products.
5. The vent system shall terminate at least 3 feet above any
forced air inlet (except direct vent units) located within 10 feet,
and at least 4 feet below, 4 feet horizontally from, or 1 foot
above any door, window, or gravity air inlet into any building.
The bottom of the vent terminal shall be located above the
snow line or at least 1 foot above grade; whichever is greater.
When located adjacent to public walkways the vent system
shall terminate not less than 7 feet above grade.
6. The venting system must be exclusive to a single unit, and
no other unit is allowed to be vented into it.
7. Horizontally vented units must use single wall vent pipe
although one continuous section of double wall vent pipe
may be used with the vent system. Under no circumstances
should two sections of double wall vent pipe be joined
together within one vent system due to the inability to verify
complete seal of inner pipes.
12" MIN
RECOMMENDED
4" MIN
TEE WITH DRIP LEG
AND CLEANOUT CAP
(SLOPE 1/4" PER
FOOT DOWNWARD
TOWARD DRIP LEG)
EXHAUST
"H" MIN*
12" MIN
RECOMMENDED
4" MIN
BACK VIEW
ROOF PITCH IS:
X / 12
TEE WITH DRIP LEG
AND CLEANOUT CAP
(SLOPE 1/4" PER
FOOT DOWNWARD
TOWARD DRIP LEG)
ROOF FLASHING
USE LISTED THIMBLE
THROUGH ROOF AND
CEILING
EXHAUST
12
X
LISTED TERMINAL
* SIZE ACCORNING
TO EXPECTED
SNOW DEPTH.
TO WALL OR ADJOINING BUILDING
2' MIN
2' MIN*
USE THIMBLE
THROUGH
CELLING
ROOF FLASHING
TERMINAL
figure 7.1 - vertical category i vent system
rise X (in)
roof Pitch
min Height H (ft)
➀
0-6
Flat to 6/12
1.00
6-7
6/12 to 7/12
1.25
7-8
7/12 to 8/12
1.50
8-9
8/12 to 9/12
2.00
9-10
9/12 to 10/12
2.50
10-11
10/12 to 11/12
3.25
11-12
11/12 to 12/12
4.00
12-14
12/12 to 14/12
5.00
14-16
14/12 to 16/12
6.00
16-18
16/12 to 18/12
7.00
18-20
18/12 to 20/12
7.50
20-21
20/12 to 21/12
8.00
table 7.1 - minimum Height from roof to lowest
discharge opening
➀
Size according to expected snow depth.
METAL
SLEEVE
FIBER GLASS
INSULATION
MIN. 2"
2" MIN.
VENT TERMINATION
SUPPORT BRACKET
(where required)
(Make from 1" x 1" steel angle)
9"
9"
45
1"
METAL
SLEEVE
2" MIN.
VENT PIPE
DIAMETER
METAL FACE
PLATE
1"
12" min
figure 7.3 - venting through combustible Walls
TEE WITH DRIP LEG
AND CLEANOUT CAP
AT LOW POINT OF
VENT SYSTEM
POWER EXHAUSTER OUTLET
PITCH VENT PIPE DOWNWARD
FROM UNIT 1/4" PER FOOT
12"
Min.
GARY STEEL
MODEL 1092 TERMINAL
figure 7.2 - Horizontal venting
installation
table 7.2 - Horizontal category iii vent sizing
requirements
model size
vent connector
diameter
minimum vent
Pipe diameter
maxium vent
length
75
4"
4"
48'
100-175
4"
4"
55'
200
6"
5"
➀
70'
225
6"
6"
70'
250-300
6"
6"
63'
350-400
6"
6"
70'
➀
Unit can be vented with 5" diameter pipe if a 6" to 5" reducer is used.
Otherwise, use 6" pipe.
