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California Mechanical Code (Part 4, Title 24, California Code of Regulations) - page 7 / 49

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Table 5-3

2007 CALIFORNIA MECHANICAL CODE

TABLE 5-3 Reduction of Clearances with Specified Forms of Protection

Where the required clearance with no protection from appliance, vent connector, or

36 in.

18 in

.

single-wall metal pipe is: 12 in.

9 in.

6 in.

Allowable Clearances with Specified Protection (in.)

Type of protection applied to and covering all surfaces of combustible material within the distance specified as the required clearance with no protection [See Figures 9-1(a) through 9-1(c)]

(1) 3-1/2 in. thick masonry wall without ventilated air- space (2) 1/2 in. insulation board over 1 in. glass fiber or mineral wool batts (3) 0.024 sheet metal over 1 in. glass fiber or mineral wool batts reinforced with wire on rear face with ventilated airspace (4) 3-1/2 in. thick masonry wall with ventilated air space (5) 0.024 sheet metal with ventilated airspace (6) 1/2 in. thick insulation board with ventilated air- space (7) 0.024 sheet metal with ventilated airspace over 0.024 sheet metal with ventilated airspace (8) 1 in. glass fiber or mineral wool batts sandwiched between two sheets 0.024 sheet metal with ventilated airspace

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

--

24

--

12

--

9

--

6

--

5

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

24

18

12

9

9

6

6

5

4

3

18

12

9

6

6

4

5

3

3

3

--

12

--

6

--

6

--

6

--

6

18

12

9

6

6

4

5

3

3

2

18

12

9

6

6

4

5

3

3

3

18

12

9

6

6

4

5

3

3

3

18

12

9

6

6

4

5

3

3

3

For SI units, 1 in. = 25.4 mm. Notes: 1 Reduction of clearances from combustible materials shall not interfere with combustion air, draft hood clearance and relief, and accessibility of servicing. 2 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. 3 Spacers and ties shall be of noncombustible material. No spacer or tie shall be used directly opposite the appliance or connector. 4 Where all clearance reduction systems use a ventilated air space, adequate provision for air circulation shall be provided as described. [See Figures 9-1(a) through 9-1(c).] 5 There shall be at least 1 in. (25 mm) between clearance reduction systems and combustible walls and ceilings for reduction systems using a ventilated airspace. 6 Where a wall protector is mounted on a single flat wall away from corners, it shall have a minimum 1 in. (25 mm) air gap. To provide adequate air circulation, the bottom and top edges, or only the side and top edges, or all edges shall be left open. 7 Mineral wool batts (blanket or board) shall have a minimum density of 8 lb./ft.3 (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 1.0 Btu in./ft.2 /hr.-˚F (0.144 W/m-K) or less. 9 There shall be at least 1 in. (25 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 Table 5-3. 10 All 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 instructions.

68

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