509.7.3 Installation With Appliances Permitted by Section 509.4
TABLE 509.7.3.4(1)
CLEARANCE FOR CONNECTORS
[NFPA 54: TABLE 12.8.4.4]*
| MINIMUM DISTANCE FROM COMBUSTIBLE MATERIAL (inches) | ||||
|---|---|---|---|---|
| APPLIANCE | LISTED TYPE B GAS VENT MATERIAL | LISTED TYPE L VENT MATERIAL | SINGLE-WALL METAL PIPE | FACTORY-BUILT CHIMNEY SECTIONS |
| Listed appliances with draft hoods and appliances listed for use with Type B gas vents | As listed | As listed | 6 | As listed |
| Residential boilers and furnaces with listed gas conversion burner and with draft hood | 6 | 6 | 9 | As listed |
| Residential appliances listed for use with Type L vents | Not permitted | As listed | 9 | As listed |
| Unlisted residential appliances with draft hood | Not permitted | 6 | 9 | As listed |
| Residential and low-heat appliances other than those above | Not permitted | 9 | 18 | As listed |
| Medium-heat appliances | Not permitted | Not permitted | 36 | As listed |
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.
Notes:
1 A — Equals the clearance with no protection specified in Table 509.7.3.4(1) and Table 509.7.3.4(2) and in the sections applying to various types of appliances.
2 B — Equals the reduced clearance permitted in accordance with Table 509.7.3.4(2).
3 The protection applied to the construction using combustible material shall extend far enough in each direction to make C equal to A.
FIGURE 509.7.3.4(1)1, 2, 3
EXTENT OF PROTECTION NECESSARY TO REDUCE CLEARANCES FROM GAS APPLIANCES OR VENT CONNECTORS
[NFPA 54: FIGURE 10.3.2.3(a)]
For SI units: 1 inch = 25.4 mm
Note: Masonry walls shall be attached to combustible walls using wall tics. Spacers shall not be used directly behind appliance or connector.
FIGURE 509.7.3.4(2)
WALL PROTECTION REDUCTION SYSTEM
[NFPA 54: FIGURE 10.3.2.3(b)]
For SI units: 1 inch = 25.4 mm
FIGURE 509.7.3.4(3)
MASONRY CLEARANCE REDUCTION SYSTEM
[NFPA 54: FIGURE 10.3.2.3(c)]
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 | 18 | 12 | 9 | 6 | 6 | 4 | 5 | 3 | 3 | 3 |
For SI units: 1 inch = 25.4 mm, °C = (°F—32)/1.8
Notes:
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 comers, 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.
- 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]