16
Harsco Industrial, Patterson-Kelley Technical Service 1.877.728.5351
INST
alla
TION
Gas Fired Boiler
n
oTICe
!
Make sure that the weight of the
vent is
not supported
by the
boiler vent collar.
the collar is
not designed to support the
weight of the vent.
Horizontal
vent sections shall be supported
in a manner to prevent sags or
low spots where condensate can
collect. Structural supports must
be connected to building elements
of sufficient strength to withstand
the weight of the vent system and
any bending forces imposed by
the venting system.
Do not locate intake or exhaust
terminations directly above a
walkway; dripping of condensation
can cause icing of the walking
surface. Maintain a minimum
clearance of 6 ft (1.83 m)
horizontally from any electric
or gas meter, regulator or relief
equipment.
!
WARNING
Conventional Vent Systems Clearances
The following termination clearance requirements are for conventional,
non-direct vent installations:
• The vent system shall terminate at least 3 ft above a forced air inlet within 10
feet horizontally.
• The vent system shall terminate at least 4 ft below, 4 ft horizontally from or 1 ft
above any door, operable window or gravity inlet into any building. The bottom of
the vent terminal shall be at least 12 in. above grade or highest expected snow
line (if applicable).
• Through the wall terminations 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 valves or other equipment.
Combustible
Non-Combustibles
Unlisted single wall metal pipe
Do NOT Use
Do NOT Use
Single wall PVC pipe
Do NOT Use
Do NOT Use
UL 1738 listed Category IV vent
Per manufacturer’s listing
Per manufacturer’s listing
Direct Vent (sealed Combustion) systems Clearances
•
The vent terminal shall be located at least 12 in. from any air opening into a
building. The bottom of the vent terminal shall be at least 12 in. above grade.
Both the vent and air intake terminals must be at least 12 in. above the highest
expected snow line.
•
Through the wall terminations 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 valves or other equipment.
•
When multiple direct vent appliances are adjacent, the exhaust must terminate
at least 10 feet horizontally or three feet vertically from the air intake of another
appliance.
3.5.3.2 Required Clearances
Forced air inlet
Less
than
10 ft.
12 in.
min.
12 in.
min.
Mechanical draft
vent terminal
Direct vent
terminal clearance
Minimum
clearance
12 in.
4 ft.
min.
12 in.
min.
4 ft.
min.
Mechanical draft
vent terminal
3 ft.
min.
Grad
e
Mechanical
draft vent
terminal
Reference: NFPA 54/ANSI Z223.1 National Fuel Gas Code
17
Harsco Industrial, Patterson-Kelley Technical Service 1.877.728.5351
INST
alla
TION
Gas Fired Boiler
The boiler vent should not be
connected into any portion of another
mechanical draft system without
consulting the vent manufacturer.
The boiler shall not be connected
to any part of a vent system serving
a Category I appliance, nor shall a
Category I appliance be connected
to any part of the vent system serving
this appliance. For CAT II common
venting refer to local venting codes.
Improper interconnection of venting
systems may result in leakage of flue
gases into occupied spaces.
!
WARNING
The condensate formed from
combustion flue gases is acidic.
The condensate shall be drained
in accordance with local code
requirements. A condensate
neutralizer may be required by
local code.
n
oTe
!
3.5.3.3 Flue Connection
The complete exhaust with
drain system is shown in the
figure. The boiler connector
(provided) is designed to
accept a 10”
OD
nominal pipe.
This connector incorporates
provisions to drain condensate
formed in the vent system
using a 3/4”
OD
drain stub. This
drain stub should be connected
with the condensate drain on
the boiler. The condensate
drains shall have a 4” tall trap
to prevent the passage of flue
gases through the condensate
system.
4” Tall Condensate Trap
The connection from the boiler to the vent should be as direct as possible
and the upward slope of any horizontal breaching should be at least 1/4
inch per linear foot.
←
The vent shall extend at least three (3) feet above the roof, or at least two
(2) feet above the highest part of any structure within ten (10) feet of the
vent. This is illustrated in the following diagram.
Additionally the boiler vent shall terminate at
least 3 ft above a forced air inlet located within
10 ft.
To prevent the possible re-circulation of flue
gases, the vent designer must take into
consideration such things as prevailing winds,
eddy zones, building configurations, etc.
harsco Industrial, Patterson-Kelley cannot
be responsible for the effects such adverse
conditions may have on the operation of the
boilers
. Dimensions listed above are minimums
and may not be sufficient for conditions at a
specific job site.
Vertical vents are allowed to be terminated
with a variety of ends, including plain straight
pipe, elbow or vent tee. Horizontal vents must
be terminated as illustrated in section 3.5.5. A
birdscreen with 1” x 1” openings is recommended
for the termination. Harsco Industrial, Patterson-
Kelley does not recommend using a vent rain
cap of any type.
3.5.3.4 Vent termination
While the vent design parameters outlined in Section 3.5.3 still apply, achieving those same parameters in a
combined vent system, adds a significant degree of complexity. Therefore, venting systems for multiple boilers
shall be designed by experienced and knowledgeable venting professionals. The venting system shall be
3.5.4 Venting for multiple Boilers
Table 3.5.3.2
Interior Component Clearances
All vent system components shall be installed so as to maintain the
following required minimum clearances:
Figure 3.5.3.2
Figure 3.5.3.3
Figure 3.5.3.4
