N.Y.C. Admin. Code § FGC 308: Section FGC 308: Clearance Reduction

308.1 Scope.

This section shall govern the reduction in required clearances to gypsum board, combustible materials and combustible assemblies for chimneys, vents, appliances, devices and equipment. Clearance requirements for air-conditioning equipment and central heating boilers and furnaces shall comply with Sections 308.3 and 308.4.

308.2 Reduction table.

The allowable clearance reduction shall be based on one of the methods specified in Table 308.2 or shall utilize a reduced clearance protective assembly listed and labeled in accordance with UL 1618. Where required clearances are not listed in Table 308.2, the reduced clearances shall be determined by linear interpolation between the distances listed in the table. Reduced clearances shall not be derived by extrapolation below the range of the table. The reduction of the required clearances to combustibles for listed and labeled appliances and equipment shall be in accordance with the requirements of this section except that such clearances shall not be reduced where reduction is specifically prohibited by the terms of the appliance or equipment listing (see Figures 308.2(1) through 308.2(3)).

Table 308.2

a through k

  Reduction of Clearances With Specified Forms of Protection

Type of Protection Applied to and Covering All Surfaces of Combustible Material Within the Distance Specified as the Required Clearance With No Protection

Where the Required Clearance With No Protection Appliance, Vent Connector, or Single-Wall Metal Pipe is: (inches)

36

18

12

9

6

Allowable clearances with specified protection (inches)

Use Column 1 for clearances above appliance or horizontal connector. Use Column 2 for clearances from appliance, vertical connector, and single-wall metal pipe.

Above Col. 1

Sides and rear Col. 2

Above Col. 1

Sides and rear Col. 2

Above Col. 1

Sides and rear Col. 2

Above Col. 1

Sides and rear Col. 2

Above Col. 1

Sides and rear Col. 2

1.

3 1/2-inch-thick masonry wall without ventilated airspace

—

24

—

12

—

9

—

6

—

5

2.

1/2-inch insulation board over1-inch glass fiber or mineral wool batts

24

18

12

9

9

6

6

5

4

3

3.

0.0296 inch (No. 22 gauge) galvanized sheet metal over 1-inch glass fiber or mineral wool batts reinforced with wire on rear face with ventilated airspace

18

12

9

6

6

4

5

3

3

3

4.

3 1/2-inch-thick masonry wall with ventilated airspace

—

12

—

6

—

6

—

6

—

6

5.

0.024-inch (nominal 24 gage) sheet metal with ventilated airspace

18

12

9

6

6

4

5

3

3

2

6.

1/2-inch thick insulation board with ventilated airspace

18

12

9

6

6

4

5

3

3

3

7.

0.024-inch (nominal 24 gage) sheet metal with ventilated airspace over 0.024-inch (nominal 24 gage) sheet metal with ventilated airspace

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 gage) sheet metal with ventilated airspace

18

12

9

6

6

4

5

3

3

3

For SI: 1 inch = 25.4 mm, °C = [(°F-32)/1.8], 1 pound per cubic foot = 16.02 kg/m

3

, 1 Btu per inch per square foot per hour per °F = 0.144 W/m

2

K.

a. Reduction of clearances from combustible materials shall not interfere with combustion air, draft hood clearance and relief, and accessibility of servicing.

b. All clearances shall be measured from the outer surface of the combustible material to the nearest point on the surface of the appliance, disregarding any intervening protection applied to the combustible material.

c. Spacers and ties shall be of noncombustible material. No spacer or tie shall be used directly opposite an appliance or connector.

d. For all clearance reduction systems using a ventilated airspace, adequate provision for air circulation shall be provided as described.

e. There shall be not less than 1 inch between clearance reduction systems and combustible walls and ceilings for reduction systems using ventilated airspace.

f. Where a wall protector is mounted on a single flat wall away from corners, it shall have a minimum 1-inch air gap. To provide air circulation, the bottom and top edges, or only the side and top edges, or all edges shall be left open.

g. Mineral wool batts (blanket or board) shall have a minimum density of 8 pounds per cubic foot and a minimum melting point of 1,500°F.

h. Insulation material used as part of a clearance reduction system shall have a thermal conductivity of 1.0 Btu per inch per square foot per hour per °F or less.

i. There shall be not less than 1 inch 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.

j. All clearances and thicknesses are minimum; larger clearances and thicknesses are acceptable.

k. Listed single-wall connectors shall be installed in accordance with the manufacturer's instructions.

Notes:

"A" equals the clearance with no protection.

"B" equals the reduced clearance permitted in accordance with Table 308.2. The protection applied to the construction using combustible materials shall extend far enough in each direction to make "C" equal to "A".

Figure 308.2(1) Extent of Protection Necessary to Reduce Clearances from Appliance or Vent Connections

For SI: 1 Inch = 25.4 mm.

Figure 308.2(2) Wall Protector Clearance Reduction System

For SI: 1 Inch = 25.4 mm.

Figure 308.2(3) Masonry Clearance Reduction System

308.3 Clearances for indoor air-conditioning appliances.

Clearance requirements for indoor air-conditioning equipment shall comply with Sections 308.3.1 through 308.3.4.

308.3.1 Appliance clearances.

Air-conditioning appliances shall be installed with clearances in accordance with the terms of their listing and the manufacturer's instructions.

308.3.2 Clearance reduction.

Air-conditioning appliances shall be permitted to be installed with reduced clearances to combustible material, provided that the combustible material or appliance is protected as described in Table 308.2 and such reduction is allowed by the manufacturer's instructions.

308.3.3 Plenum clearances.

Where the furnace plenum is adjacent to plaster on metal lath or noncombustible material attached to combustible material, the clearance shall be measured to the surface of the plaster or other noncombustible finish where the clearance specified is 2 inches (50.8 mm) or less.

308.3.4 Clearance from supply ducts.

Supply air ducts connecting to listed central heating furnaces shall have the same minimum clearance to combustibles as required for the furnace supply plenum for a distance of not less than 3 feet (914.4 mm) from the supply plenum. Clearance is not required beyond the 3-foot (914.4 mm) distance.

308.4 Central-heating boilers and furnaces.

Clearance requirements for central-heating boilers and furnaces shall comply with Sections 308.4.1 through 308.4.5. The clearance to these appliances shall not interfere with combustion air; draft hood clearance and relief; and accessibility for servicing.

308.4.1 Appliance clearances.

Central-heating furnaces and low-pressure boilers shall be installed with clearances in accordance with the manufacturer's instructions.

308.4.2 Clearance reduction.

Central-heating furnaces and low-pressure boilers shall be permitted to be installed with reduced clearances to combustible material provided that such reduction is allowed by the manufacturer's instructions and the combustible material or appliance is protected as described in Table 308.2.

308.4.3 Clearance for servicing appliances.

Front clearance shall be sufficient for servicing the burner and the furnace or boiler.

308.4.4 Plenum clearances.

Where the furnace plenum is adjacent to plaster on metal lath or noncombustible material attached to combustible material, the clearance shall be measured to the surface of the plaster or other noncombustible finish where the clearance specified is 2 inches (50.8 mm) or less.

308.4.5 Clearance from supply ducts.

Supply air ducts connecting to listed central heating furnaces shall have the same minimum clearance to combustibles as required for the furnace supply plenum for a distance of not less than 3 feet (914.4 mm) from the supply plenum. Clearance is not required beyond the 3-foot (914.4 mm) distance.