Install Instructions

10
6-583.4
INSTALLATION - VENTING
Section C – Horizontal, Category III Vent System
Installation
C1. This section applies to horizontally vented Category III
vent systems and is in addition to “Section A – General
Instructions – All Units”.
C2. All heaters that are horizontally vented with 3" (for sizes
30-75) or 4" (for sizes 100 and 125) vent pipe perform as
a Category III appliance. Category III venting has special
venting requirements as follows:
• Allresidential, horizontally vented Category III heaters
must be vented with an agency certified (UL1738)
Category III venting system. Agency certified Category
III venting systems are available from your local vent
pipe distributor. Follow the agency certified Category III
vent manufacturer's instructions for installation.
• Forcommercial and industrial horizontally vented
heaters you may use either agency certified Category
III venting systems as noted above, or single wall
galvanized or stainless steel vent pipe. If single wall
vent pipe is used, all seams and joints must be sealed
with metallic tape or silastic suitable for temperatures
up to 400°F. Wrap the tape two full turns around the
vent pipe. For single wall vent systems, one continuous
section of double wall vent pipe may be used within
the vent system. Refer to instruction A10 in “Section A
– General Instructions – All Units” for attaching double
wall pipe to single wall pipe.
C3. Limit the total equivalent vent pipe length to a minimum of 3'
and a maximum of 30', making the vent system as straight
as possible. The equivalent length of a 3" elbow is 1' and for
a 4” elbow is 5’.
C4. All horizontal Category III vents must be terminated with
a Gary Steel 1092 vent cap. The cap must terminate a
minimum distance from the external wall, as summarized in
Table 10.1.
➀ Refer to Figure 10.2 and 10.3.
C5. The vent must be supported as shown in Figure 10.1.
C6. When condensation may be a problem, the vent system shall
not terminate over public walkways or over an area where
condensate or vapor could create a nuisance or hazard or
could be detrimental to the operation of regulators, relief
openings, or other equipment.
C7. The venting system must be exclusive to a single unit, and
no other unit is allowed to be vented into it.
C8. When vented horizontally, maintain a 1/4" per foot rise away
from the heater and place a drip leg with clean out near the
unit as shown in Figure 10.2. Where local authorities have
jurisdiction, a 1/4" per foot downward slope is acceptable
with a drip leg and clean out near the exit of the vent as
shown in Figure 10.3, or allow the condensate to drip out the
end.
C9. For a vent termination located under an eave, the distance
of the overhang must not exceed 24". The clearance to
combustibles above the exterior vent must be maintained
at a minimum of 12". Consult the National Fuel Gas Code
for additional requirements for eaves that have ventilation
openings.
C10. Once venting is complete, proceed to the section titled
“Installation – Gas Connections”.
Table 10.1 - Minimum Length Between External
Wall and Vent
Model Min. Length
Size Application A ➀
30-75 Residential & Commercial 11"
100, 125 Residential 12"
100, 125 Commercial 24"
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"
Figure 10.1 - Exhaust Vent Construction Through
Combustible Walls and Support Bracket
Figure 10.2 - Horizontal Category III Venting with
Upward Pitch
1
/4" Slope per foot up towards termination
Drip leg / Clean out cap
6"
Above
snow
grade
Listed Thimble
A
Specified Terminal
3' Min
30' Max
Figure 10.3 - Horizontal Category III Venting with
Downward Pitch (with drip leg)
1
/4" Slope per foot down towards termination
Listed
Thimble
A
3' Min
30' Max
Specified Terminal
Drip leg / Clean out cap