Use and Care Manual

10
6-583.12
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”. Category III vent systems listed by
a nationally recognized agency and matching the diameters
specified may be used. Different brands of vent pipe
materials may not be intermixed. Under no circumstances
should two sections of double wall vent pipe be joined together
within one horizontal vent system due to the inability to verify
complete seal of inner pipes.
C2. All heaters that are horizontally vented 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. For single wall vent systems,
one continuous section of double wall vent pipe may be
used within the vent system to pass through the wall to
the listed terminal. Refer to instruction A10 in “Section A –
General Instructions – All Units” for attaching double wall
pipe to single wall pipe. If un-gasketed 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 (3M
aluminum foil tapes 433 or 363 are acceptable). Wrap tape
two full turns around the vent pipe.
C3. All horizontal Category III vents must be terminated with a
listed vent cap. The cap must terminate a minimum distance
from the external wall, as summarized in Table 10.1.
C4. The vent must be supported as shown in Figure 10.1.
C5. 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.
INSTALLATION - VENTING
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
Listed 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
Listed Terminal
Drip leg / Clean out cap
Table 10.1 - Minimum Length Between External
Wall and Vent
Model Min. Length
Size Application A j
30-75 Residential & Commercial 11"
100, 125 Residential 12"
100, 125 Commercial 24"
j Refer to Figure 10.2 and 10.3.
C6. The venting system must be exclusive to a single unit, and
no other unit is allowed to be vented into it.
C7. 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.
C8. 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.
C9. Once venting is complete, proceed to the section titled
“Installation – Gas Connections”.