Single-wall metal pipe
shall be used for runs directly from the space in
which the appliance is located through the roof or
exterior wall to the outer air. A pipe passing through
a roof shall extend without interruption through the
roof flashing, roof jacket, or roof thimble. [NFPA
54:12.8.4.2]
Single-wall
metal pipe shall not originate in an unoccupied
attic or concealed space and shall not pass through
an attic, inside wall, concealed space, or floor. [NFPA 54:12.8.4.3]
Single-wall metal pipe used
for venting an incinerator shall be exposed and readily
examinable for its full length and shall have
required clearances maintained.
Minimum clearances from
single-wall metal pipe to combustible material shall
be in accordance with Table 509.7.3.4(1). Reduced
clearances from single-wall metal pipe to combustible
material shall be as specified for vent connectors
in Table 509.7.3.4(2). [NFPA 54:12.8.4.4]
For SI units: 1 inch = 25.4 mm
* These clearances shall apply unless the installation instructions of a listed appliance or connector specify different clearances, in which case the listed clearances shall apply.
TABLE 509.7.3.4(2)
REDUCTION OF CLEARANCES WITH SPECIFIED FORMS OF PROTECTION1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
[NFPA 54: TABLE 10.2.3]
TYPE OF PROTECTION APPLIED TO AND COVERING ALL SURFACES OF COMBUSTIBLE MATERIAL WITHIN THE DISTANCE SPECIFIED AS THE REQUIRED CLEARANCE WITH NO PROTECTION [SEE FIGURE 509.7.3.4(1) THROUGH FIGURE 509.7.3.4(3)]
WHERE THE REQUIRED CLEARANCE WITH NO PROTECTION FROM APPLIANCE, VENT CONNECTOR, OR SINGLE-WALL METAL PIPE IS:
36 (inches)
18 (inches)
12 (inches)
9 (inches)
6 (inches)
ALLOWABLE CLEARANCES WITH SPECIFIED PROTECTION (inches)
USE COLUMN 1 FOR CLEARANCES ABOVE APPLIANCE OR HORIZONTAL CONNECTOR. USE COLUMN 2 FOR CLEARANCES FROM APPLIANCES, VERTICAL CONNECTOR, AND SINGLE-WALL METAL PIPE.
ABOVE COLUMN 1
SIDES AND REAR COLUMN 2
ABOVE COLUMN 1
SIDES AND REAR COLUMN 2
ABOVE COLUMN
1
SIDES AND REAR COLUMN 2
ABOVE COLUMN 1
SIDES AND REAR COLUMN 2
ABOVE COLUMN 1
SIDES AND REAR COLUMN 2
(1) 31/2 inch thick masonry wall without ventilated air space
-
24
-
12
-
9
-
6
-
5
(2) 1/2 of an inch insulation board over 1 inch glass fiber or mineral wool batts
24
18
12
9
9
6
6
5
4
3
(3) 0.024 inch (nominal 24 gauge) sheet metal over 1 inch glass fiber or mineral wool batts reinforced with wire on rear face with ventilated air space
18
12
9
6
6
4
5
3
3
3
(4) 31/2 inch thick masonry wall with ventilated air space
-
12
-
6
-
6
-
6
-
6
(5) 0.024 inch (nominal 24 gauge) sheet metal with ventilated air space
18
12
9
6
6
4
5
3
3
2
(6) 1/2 of an inch thick insulation board with ventilated air space
18
12
9
6
6
4
5
3
3
3
(7) 0.024 inch (nominal 24 gauge) sheet metal with ventilated air space over 0.024 inch (nominal 24 gauge) sheet metal with ventilated air space
18
12
9
6
6
4
5
3
3
3
(8) 1 inch glass fiber or mineral wool batts sandwiched between two sheets 0.024 inch (nominal 24 gauge) sheet metal with ventilated air space
1 Reduction of clearances from combustible materials shall not interfere with combustion air, draft hood clearance and relief, and accessibility of servicing.
2 Clearances shall be measured from the outer surface of the combustible material to the nearest point on the surface of the appliance, disregarding an intervening
protection applied to the combustible material.
3 Spacers and ties shall be of noncombustible material. No spacer or tie shall be used directly opposite the appliance or connector.
4 Where clearance reduction systems use a ventilated air space, adequate provision for air circulation shall be provided as described. [See Figure 509.7.3.4(2)
and Figure 509.7.3.4(3)]
5 There shall be not less than 1 inch (25.4 mm) between clearance reduction systems and combustible walls and ceilings for reduction systems using a ventilated
air space.
6 Where a wall protector is mounted on a single flat wall away from corners, it shall have a minimum 1 inch (25.4 mm) air gap. To provide air circulation, the
bottom and top edges, or only the side and top edges, or edges shall be left open.
7 Mineral wool batts (blanket or board) shall have a minimum density of 8 pounds per cubic foot (lb/ft3) (128 kg/m3) and a minimum melting point of 1500°F
(816°C).
8 Insulation material used as part of a clearance reduction system shall have a thermal conductivity of 1 British thermal unit inch per hour square foot degree
Fahrenheit [Btu•in/(h•ft2•°F)] [0.1 W/(m•K)] or less.
9 There shall be not less than 1 inch (25.4 mm) between the appliance and the protector. In no case shall the clearance between the appliance and the combustible
surface be reduced below that allowed in this table.
10 Clearances and thicknesses are minimum; larger clearances and thicknesses are acceptable.
11 Listed single-wall connectors shall be installed in accordance with the terms of their listing and the manufacturer's installation instructions.
Single-wall
metal pipe shall not pass through a combustible
exterior wall unless guarded at the point of passage
by a ventilated metal thimble not smaller than the
following:
For listed appliances with draft hoods and appliances
listed for use with Type B gas vents, the
thimble shall be a minimum of 4 inches (100 mm) larger in diameter than the metal pipe. Where there is a run of not less than 6 feet
(1829 mm) of metal pipe in the opening
between the draft hood outlet and the thimble,
the thimble shall be a minimum of 2 inches (50
mm) larger in diameter than the metal pipe.
For unlisted appliances having draft hoods, the
thimble shall be a minimum of 6 inches (150
mm) larger in diameter than the metal pipe.
For residential and low-heat appliances, the
thimble shall be a minimum of 12 inches (300
mm) larger in diameter than the metal pipe.
Exception: In lieu of thimble protection, all combustible
material in the wall shall be removed a sufficient
distance from the metal pipe to provide the
specified clearance from such metal pipe to combustible
material. Any material used to close up such
opening shall be noncombustible. [NFPA 54:12.8.4.6]
Where a single-wall
metal pipe passes through a roof constructed of combustible
material, a noncombustible, nonventilating
thimble shall be used at the point of passage. The
thimble shall extend not less than 18 inches (457
mm) above and 6 inches (152 mm) below the roof
with the annular space open at the bottom and closed
at the top. The thimble shall be sized in accordance
with Section 509.7.3.5. [NFPA 54:12.8.4.5]
with Section 716.2.6.6. Doors shall not have air transfer openings and shall not be undercut in excess of the clearance permitted in accordance with NFPA ...