READ ONLY. Adopting Agency BSC SFM. Adopt Entire Chapter Adopt Entire Chapter as amended (amended sections listed below)

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1 CALIFORNIA MECHANICAL CODE MATRIX ADOPTION TABLE APPENDIX F SIZING OF VENTING SYSTEMS SERVING APPLIANCES EQUIPPED WITH DRAFT HOODS, CATEGORY I APPLIANCES, AND APPLIANCES LISTED FOR USE WITH TYPE B VENTS. (Matrix Adoption Tables are non-regulatory, intended only as an aid to the user. See Chapter 1 for state agency authority and building application.) Adopting Agency BSC SFM Adopt Entire Chapter Adopt Entire Chapter as amended (amended sections listed below) HCD DSA OSHPD AC AC SS SS/CC BSCC DPH AGR DWR CA SL SLC Adopt only those sections that are listed below Chapter/Section 2013 CALIFORNIA MECHANICAL CODE 433

2 CALIFORNIA MECHANICAL CODE

3 SIZING OF VENTING SYSTEMS SERVING APPLIANCES EQUIPPED WITH DRAFT HOODS, CATEGORY I APPLIANCES, AND APPLIANCES LISTED FOR USE WITH TYPE B VENTS. (The content of this Appendix is based on Annex G and Annex J of NFPA 54) F 1.0 Examples Using Single Appliance Venting Tables. [See Figure F 1.0(a) through Figure F 1.0(n)] Table (1) is used where sizing a Type B double-wall gas vent connected directly to the appliance. Note: The appliance is permitted to be either Category I draft hood-equipped or fan-assisted type. FIGURE F 1.0(a) TYPE B DOUBLE-WALL VENT SYSTEM SERVING A SINGLE APPLIANCE WITH A TYPE B DOUBLE-WALL VENT Table (2) is used where sizing a single-wall metal vent connector attached to a Type B double-wall gas vent. Note: The appliance is permitted to be either Category I draft hood-equipped or fan-assisted type. FIGURE F 1.0(b) TYPE B DOUBLE-WALL VENT SYSTEM SERVING A SINGLE APPLIANCE WITH A SINGLE-WALL METAL VENT CONNECTOR Table (3) is used where sizing a Type B double-wall gas vent connector attached to a tile-lined masonry chimney. Notes: 1. A is the equivalent cross-sectional area of the tile liner. 2. The appliance is permitted to be either Category I draft hood-equipped or fan-assisted type. FIGURE F 1.0(c) VENT SYSTEM SERVING A SINGLE APPLIANCE WITH A MASONRY CHIMNEY AND A TYPE B DOUBLE-WALL VENT CONNECTOR 2013 CALIFORNIA MECHANICAL CODE 435

4 Table (4) is used where sizing a single-wall vent connector attached to a tile-lined masonry chimney. Notes: 1. A is the equivalent cross-sectional area of the tile liner. 2. The appliance is permitted to be either Category I draft hood-equipped or fan-assisted type. FIGURE F 1.0(d) VENT SYSTEM SERVING A SINGLE APPLIANCE USING A MASONRY CHIMNEY AND A SINGLE-WALL METAL VENT CONNECTOR Table (7) is used where sizing Type B double-wall gas vent connectors attached to a Type B double-wall common vent. Note: Each appliance is permitted to be either Category I draft hoodequipped or fan-assisted type. FIGURE F 1.0(f) VENT SYSTEM SERVING TWO OR MORE APPLIANCES WITH TYPE B DOUBLE-WALL VENT AND TYPE B DOUBLE-WALL VENT CONNECTORS Table (8) is used where sizing single-wall vent connectors attached to a Type B double-wall common vent. Asbestos cement Type B or single-wall metal vent serving a single draft hood-equipped appliance. [See Table (5)] FIGURE F 1.0(e) ASBESTOS CEMENT TYPE B OR SINGLE-WALL METAL VENT SYSTEM SERVING A SINGLE DRAFT HOOD-EQUIPPED APPLIANCE Note: Each appliance is permitted to be either Category I draft hoodequipped or fan-assisted type. FIGURE F 1.0(g) VENT SYSTEM SERVING TWO OR MORE APPLIANCES WITH TYPE B DOUBLE-WALL VENT AND SINGLE-WALL METAL VENT CONNECTORS CALIFORNIA MECHANICAL CODE

5 See Section Table (9) is used where sizing Type B double-wall vent connectors attached to a tile-lined masonry chimney. Notes: 1. A is the equivalent cross-sectional area of the tile liner. 2. The appliance is permitted to be either Category I draft hood-equipped or fan-assisted type. FIGURE F 1.0(h) MASONRY CHIMNEY SERVING TWO OR MORE APPLIANCES WITH TYPE B DOUBLE-WALL VENT CONNECTORS Asbestos cement Type B or single-wall metal pipe vent serving two or more draft hood-equipped appliances. [See Table (11)] FIGURE F 1.0(j) ASBESTOS CEMENT TYPE B OR SINGLE-WALL METAL VENT SYSTEMS SERVING TWO OR MORE DRAFT HOOD- EQUIPPED APPLIANCES Table (10) is used where sizing single-wall metal vent connectors attached to a tile-lined masonry chimney. Notes: 1. A is the equivalent cross-sectional area of the tile liner. 2. Each appliance is permitted to be either Category I draft hood-equipped or fan-assisted type. FIGURE F 1.0(i) MASONRY CHIMNEY SERVING TWO OR MORE APPLIANCES WITH SINGLE-WALL METAL VENT CONNECTORS Example: Manifolded common vent connector L M shall not exceed 18 times the common vent connector manifold inside diameter; that is, a 4 inch (102 mm) inside diameter common vent connector manifold shall not exceed 72 inches (1829 mm) in length. Note: This is an illustration of a typical manifolded vent connector. Different appliance, vent connector, or common vent types are possible. FIGURE F 1.0(k) USE OF MANIFOLDED COMMON VENT CONNECTORS 2013 CALIFORNIA MECHANICAL CODE 437

6 See Section Example: Offset common vent Note: This is an illustration of a typical offset vent. Different appliance, vent connector, or vent types are possible. FIGURE F 1.0(l) USE OF OFFSET COMMON VENT FIGURE F 1.0(n) PRINCIPLES OF DESIGN OF MULTISTORY VENTS USING VENT CONNECTOR AND COMMON VENT DESIGN TABLES F 1.1 Example 1: Single Draft Hood-Equipped Appliance. An installer has a British thermal units per hour (Btu/h) (35 kw) input appliance with a 5 inch (127 mm) diameter draft hood outlet that needs to be vented into a 10 foot (3048 mm) high Type B vent system. What size vent should be used assuming: (1) a 5 foot (1524 mm) lateral single-wall metal vent connector is used with two 90 degree (1.57 rad) elbows or (2) a 5 foot (1524 mm) lateral singlewall metal vent connector is used with three 90 degree (1.57 rad) elbows in the vent system? (See Figure F 1.1) FIGURE F 1.0(m) MULTISTORY GAS VENT DESIGN PROCEDURE FOR EACH SEGMENT OF SYSTEM Table (2) shall be used to solve this problem because single-wall metal vent connectors are being used with a Type B vent, as follows: CALIFORNIA MECHANICAL CODE

7 (1) Read down the first column in Table (2) until the row associated with a 10 foot (3048 mm) height and 5 foot (1524 mm) lateral is found. Read across this row until a vent capacity exceeding Btu/h (35 kw) is located in the shaded columns labeled NAT Max for draft hood-equipped appliances. In this case, a 5 inch (127 mm) diameter vent has a capacity of Btu/h (35.7 kw) and shall be permitted to be used for this application. (2) Where three 90 degree (1.57 rad) elbows are used in the vent system, the maximum vent capacity listed in the tables shall be reduced by 10 percent. This implies that the 5 inch (127 mm) diameter vent has an adjusted capacity of only Btu/h (32 kw). In this case, the vent system shall be increased to 6 inches (152 mm) in diameter. See the following calculations: Btu/h (35.7 kw) x 0.90 = Btu/h (32 kw) for 5 inch (127 mm) vent From Table (3), select 6 inch (152 mm) vent Btu/h (54.5 kw) x 0.90 = Btu/h (49 kw) This figure is exceeding the required Btu/h (35 kw). Therefore, use a 6 inch (152 mm) vent and connector where three elbows are used. Table (2) refers to the use of single-wall metal vent connectors with Type B vent. In the first column find the row associated with a 30 foot (9144 mm) height and a 10 foot (3048 mm) lateral. Read across this row, looking at the FAN Min and FAN Max columns, to find that a 3 inch (76 mm) diameter single-wall metal vent connector is not recommended. Moving to the next larger size single-wall connector 4 inch (102 mm), we find that a 4 inch (102 mm) diameter single-wall metal connector has a recommended maximum vent capacity of Btu/h (42 kw). The Btu/h (23.4 kw) fan-assisted appliance is outside this range, so the conclusion is that a single-wall metal connector shall be used to vent the appliance. Table (2) shows the acceptable range of vent capacities for a 4 inch (102 mm) vent with 5 feet (1524 mm) of lateral to be between Btu/h (21.1 kw) and Btu/h (46 kw). Where the appliance cannot be moved closer to the vertical vent, then a Type B vent shall be used as the connector material. In this case, Table (1) shows that, for a 30 foot (9144 mm) high vent with 10 feet (3048 mm) of lateral, the acceptable range of vent capacities for a 4 inch (102 mm) diameter vent attached to a fan-assisted appliance is between Btu/h (10.8 kw) and Btu/h (44 kw). For SI units: 1 foot = mm, 1000 British thermal units per hour = kw FIGURE F 1.1 SINGLE DRAFT HOOD-EQUIPPED APPLIANCE EXAMPLE 1 For SI units: 1 foot = mm, 1000 British thermal units per hour = kw FIGURE F 1.2 SINGLE FAN-ASSISTED APPLIANCE EXAMPLE 2 F 1.2 Example 2: Single Fan-Assisted Appliance. An installer has an Btu/h (23.4 kw) input fan-assisted appliance that shall be installed using 10 feet (3048 mm) of lateral connector attached to a 30 foot (9144 mm) high Type B vent. Two 90 degree (1.57 rad) elbows are needed for the installation. Is a single-wall metal vent connector permitted to be used for this application? (See Figure F 1.2) F 1.3 Example 3: Interpolating Between Table Values. An installer has an Btu/h (23.4 kw) input appliance with a 4 inch (102 mm) diameter draft hood outlet that needs to be vented into a 12 foot (3658 mm) high Type B vent. The vent connector has a 5 foot (1524 mm) lateral length and is also Type B vent. Is this appliance permitted to be vented using a 4 inch (102 mm) diameter vent? 2013 CALIFORNIA MECHANICAL CODE 439

8 Table (1) is used in the case of an all Type B Vent system. However, since there is no entry in Table (1) for a height of 12 feet (3658 mm), interpolation shall be used. Read down the 4 inch (102 mm) diameter NAT Max column to the row associated with a 10 foot (3048 mm) height and 5 foot (1524 mm) lateral to find the capacity value of Btu/h (22.6 kw). Read further down to the 15 foot (4572 mm) height, 5 foot (1524 mm) lateral row to find the capacity value of Btu/h (25.5 kw). The difference between the 15 foot (4572 mm) height capacity value and the 10 foot (3048 mm) height capacity value is Btu/h (3 kw). The capacity for a vent system with a 12 foot (3658 mm) height is equal to the capacity for a 10 foot (3048 mm) height plus two-fifths of the difference between the 10 foot (3048 mm) and 15 foot (4572 mm) height values, or Btu/h (22.6 kw) x Btu/h (3 kw) = Btu/h (23.7 kw). Therefore, a 4 inch (102 mm) diameter vent shall be used in the installation. F 2.0 Examples Using Common Venting Tables. F 2.1 Example 4: Common Venting Two Draft Hood- Equipped Appliances. A Btu/h (10.3 kw) water heater is to be common vented with a Btu/h (44 kw) furnace, using a common vent with a total height of 30 feet (9144 mm). The connector rise is 2 feet (610 mm) for the water heater with a horizontal length of 4 feet (1219 mm). The connector rise for the furnace is 3 feet (914 mm) with a horizontal length of 8 feet (2438 mm). Assume single-wall metal connectors will be used with Type B vent. What size connectors and combined vent should be used in this installation? (See Figure F 2.1) Table (8) shall be used to size single-wall metal vent connectors attached to Type B vertical vents. In the vent connector capacity portion of Table (8), find the row associated with a 30 foot (9144 mm) vent height. For a 2 foot (610 mm) rise on the vent connector for the water heater, read the shaded columns for draft hood-equipped appliances to find that a 3 inch (76 mm) diameter vent connector has a capacity of Btu/h (10.8 kw). Therefore, a 3 inch (76 mm) single-wall metal vent connector shall be used with the water heater. For a draft hood-equipped furnace with a 3 foot (914 mm) rise, read across the row to find that a 5 inch (127 mm) diameter vent connector has a maximum capacity of Btu/h (35 kw) (which is too small for the furnace), and a 6 inch (152 mm) diameter vent connector has a maximum vent capacity of Btu/h (50 kw). Therefore, a 6 inch (152 mm) diameter vent connector shall be used with the Btu/h (44 kw) furnace. Since both vent connector horizontal lengths are less than the maximum lengths listed in Section , the table values shall be used without adjustments. In the common vent capacity portion of Table (8), find the row associated with a 30 foot (9144 mm) vent height and read over to the NAT + NAT portion of the 6 inch (152 mm) diameter column to find a maximum combined capacity of Btu/h (75 kw). Since the two appliances total Btu/h (54 kw), a 6 inch (152 mm) common vent shall be used. For SI units: 1 foot = mm, 1000 British thermal units per hour = kw FIGURE F 2.1 COMMON VENTING TWO DRAFT HOOD-EQUIPPED APPLIANCES EXAMPLE 4 F 2.2 Example 5(a): Common Venting a Draft Hood- Equipped Water Heater with a Fan-Assisted Furnace into a Type B Vent. In this case, a Btu/h (10.3 kw) input draft hood-equipped water heater with a 4 inch (102 mm) diameter draft hood outlet, 2 feet (610 mm) of connector rise, and 4 feet (1219 mm) of horizontal length is to be common vented with a Btu/h (29 kw) fan-assisted furnace with a 4 inch (102 mm) diameter flue collar, 3 feet (914 mm) of connector rise, and 6 feet (1829 mm) of horizontal length. The common vent consists of a 30 foot (9144 mm) height of Type B vent. What are the recommended vent diameters for each connector and the common vent? The installer would like to use a single-wall metal vent connector. (See Figure F 2.2) Solution [See Table (8)]: Water Heater Vent Connector Diameter. Since the water heater vent connector horizontal length of 4 feet (1219 mm) is less than the maximum value listed in Table (8), the venting table values shall be used without adjustment. Using the Vent Connector Capacity portion of Table (8), read down the Total Vent Height (H) column to 30 feet (9144 mm) and read across the 2 feet (610 mm) Connector Rise (R) row to the first Btu/h rating in the NAT Max column that is equal to or exceeding the water heater input rating. The table shows that a 3 inch (76 mm) vent connector has a maximum input rating of Btu/h (10.8 kw). Although this rating is exceeding the water heater input rating, a 3 inch (76 mm) vent connector is prohibited by Section A 4 inch (102 mm) vent connector has a maximum input rating of CALIFORNIA MECHANICAL CODE

9 Btu/h (19.6 kw) and is equal to the draft hood outlet diameter. A 4 inch (102 mm) vent connector is selected. Since the water heater is equipped with a draft hood, there are no minimum input rating restrictions. Furnace Vent Connector Diameter. Using the Vent Connector Capacity portion of Table (8), read down the Total Vent Height (H) column to 30 feet (9144 mm) and across the 3 feet (914 mm) Connector Rise (R) row. Since the furnace has a fan-assisted combustion system, find the first FAN Max column with a Btu/h rating exceeding the furnace input rating. The 4 inch (102 mm) vent connector has a maximum input rating of Btu/h (34.9 kw) and a minimum input rating of Btu/h (24.9 kw). The Btu/h (29 kw) furnace in this example falls within this range, so a 4 inch (102 mm) connector shall be permitted. Since the furnace vent connector horizontal length of 6 feet (1829 mm) is less than the maximum value listed in Section , the venting table values shall be used without adjustment. Where the furnace had an input rating of Btu/h (23.4 kw), then a Type B vent connector shall be needed in order to meet the minimum capacity limit. [See Table (7)] Common Vent Diameter. The total input to the common vent is Btu/h (40 kw). Using the Common Vent Capacity portion of Table (8), read down the Vent Height (H) column to 30 feet (9144 mm) and across this row to find the smallest vent diameter in the FAN + NAT column that has a Btu/h rating equal to or exceeding Btu/h (40 kw). The 4 inch (102 mm) common vent has a capacity of Btu/h (39 kw) and the 5 inch (127 mm) common vent has a capacity of Btu/h (59 kw). Therefore, the 5 inch (127 mm) common vent shall be used in this example. Summary: In this example, the installer shall use a 4 inch (102 mm) diameter, single-wall metal vent connector for the water heater and a 4 inch (102 mm) diameter, single-wall metal vent connector for the furnace. The common vent shall be a 5 inch (127 mm) diameter Type B vent. For SI units: 1 foot = mm, 1000 British thermal units per hour = kw FIGURE F 2.2 COMMON VENTING A DRAFT HOOD-EQUIPPED WATER HEATER WITH A FAN-ASSISTED FURNACE INTO A TYPE B DOUBLE-WALL COMMON VENT EXAMPLE 5(a) F 2.3 Example 5(b): Common Venting into an Interior Masonry Chimney. In this case, the water heater and fanassisted furnace of Example 5(a) are to be common-vented into a clay-tile-lined masonry chimney with a 30 foot (9144 mm) height. The chimney is not exposed to the outdoors below the roof line. The internal dimensions of the clay tile liner are nominally 8 inches (203 mm) by 12 inches (305 mm). Assuming the same vent connector heights, laterals, and materials found in Example 5(a), what are the recommended vent connector diameters, and is this an acceptable installation? Table (10) is used to size common venting installations involving single-wall connectors into masonry chimneys. Water Heater Vent Connector Diameter. Using Table (10), Vent Connector Capacity, read down the Vent Height (H) column to 30 feet (9144 mm), and read across the 2 feet (610 mm) Connector Rise (R) row to the first Btu/h rating in the NAT Max column that is equal to or exceeding the water heater input rating. The table shows that a 3 inch (76 mm) vent connector has a maximum input of Btu/h (9 kw), while a 4 inch (102 mm) vent connector has a maximum input of Btu/h (16.7 kw). A 4 inch (102 mm) vent connector shall be used. Furnace Vent Connector Diameter. Using the Vent Connector Capacity portion of Table (10), read down the total Vent Height (H) column to 30 feet (9144 mm) and across the 3 feet (914 mm) Connector Rise (R) row. Because the furnace has a fan-assisted combustion system, find the first FAN Max column with a Btu/h rating exceeding the furnace input rating. The 4 inch (102 mm) vent connector has a maximum input rating of Btu/h (37 kw) and an input rating of not less than Btu/h (27.8 kw). The Btu/h (29 kw) furnace in this example falls within this range, so a 4 inch (102 mm) connector shall be permitted. Masonry Chimney. From Table F 2.3, the equivalent area for a nominal liner size of 8 inches (203 mm) by 12 inches (305 mm) is 63.6 of a square inch (0.041 m 2 ). Using Table (10), Common Vent Capacity, read down the FAN + NAT column under the Minimum Internal Area of Chimney value of 63 to the row for 30 foot (9144 mm) height to find a capacity value of Btu/h (217 kw). The combined input rating of the furnace and water heater, Btu/h (40 kw), is less than the table value so this is an acceptable installation. Section requires the common vent area to not exceed seven times the smallest listed appliance categorized vent area, flue collar area, or draft hood outlet area. Both appliances in this installation have 4 inch (102 mm) diameter outlets. From Table F 2.3, the equivalent area for an inside diameter of 4 inches (102 mm) is 12.2 of a square inch (0.008 m 2 ). Seven times 12.2 equals 85.4, which is exceeding 63.6, so this configuration is acceptable CALIFORNIA MECHANICAL CODE 441

10 F 2.4 Example 5(c): Common Venting into an Exterior Masonry Chimney. In this case, the water heater and fanassisted furnace of Example 5(a) and Example 5(b) are to be common-vented into an exterior masonry chimney. The chimney height, clay-tile-liner dimensions, and vent connector heights and laterals are the same as in Example 5(b). This system is being installed in Charlotte, North Carolina. Does this exterior masonry chimney need to be relined? Where so, what corrugated metallic liner size is recommended? What vent connector diameters are recommended? According to Section , Type B vent connectors are required to be used with exterior masonry chimneys. Use Table (14) and Table (15) to size FAN+NAT NOMINAL LINER SIZE (Inches) INSIDE DIMENSIONS OF LINER (Inches) common venting installations involving Type-B double-wall connectors into exterior masonry chimneys. The local 99 percent winter design temperature needed to use Table (14) and Table (15) shall be found in the ASHRAE Handbook Fundamentals. For Charlotte, North Carolina, this design temperature is 19 F (-7.2 C). Chimney Liner Requirement. As in Example 5(b), use the 63 square inch (0.04 m 2 ) column of Table (14) to the 30 foot (9144 mm) height row to find that the combined appliance maximum input is Btu/h (218.9 kw). The combined input rating of the appliance in this installation, Btu/h (40 kw), is less than the maximum value, so this criterion is satisfied. Table (15), at a 19 F (-7.2 C) design temperature, and at the same vent height and internal area used earlier, shows that the minimum allowable input rating of a spaceheating appliance is Btu/h (137.7 kw). The furnace TABLE F 2.3 MASONRY CHIMNEY LINER DIMENSIONS WITH CIRCULAR EQUIVALENTS* INSIDE DIAMETER OR EQUIVALENT DIAMETER (Inches) EQUIVALENT AREA (Square Inches) x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x For SI units, 1 inch. = 25.4 mm, 1 square inch = m 2 * Where liner sizes differ dimensionally from those shown in this table, equivalent diameters shall be permitted to be determined from published tables for square and rectangular ducts of equivalent carrying capacity or by other engineering methods CALIFORNIA MECHANICAL CODE

11 input rating of Btu/h (29 kw) is less than this minimum value. So this criterion is not satisfied, and an alternative venting design shall be used, such as a Type B vent shown in Example 5(a) or a listed chimney liner system shown in the rest of the example. According to Section , Table (7) or Table (8) are used for sizing corrugated metallic liners in masonry chimneys, with the maximum common vent capacities reduced by 20 percent. This example will be continued assuming Type B vent connectors. Water Heater Vent Connector Diameter. Using Table (7) Connector Capacity, read down the total Vent Height (H) column to 30 feet (9144 mm), and read across the 2 feet (610 mm) Connector Rise (R) row to the first Btu/hour rating in the NAT Max column that is equal to or exceeding the water heater input rating. The table shows that a 3 inch (76 mm) vent connector has a maximum capacity of Btu/h (11.4 kw). Although this rating is exceeding the water heater input rating, a 3 inch (76 mm) vent connector is prohibited by Section A 4 inch (102 mm) vent connector has a maximum input rating of Btu/h (20.5 kw) and is equal to the draft hood outlet diameter. A 4 inch (102 mm) vent connector is selected. Furnace Vent Connector Diameter. Using Table (7), Vent Connector Capacity, read down the total Vent Height (H) column to 30 feet (9144 mm), and read across the 3 feet (914 mm) Connector Rise (R) row to the first Btu/h rating in the FAN MAX column that is equal to or exceeding the furnace input rating. The Btu/h (29 kw) furnace in this example falls within this range, so a 4 inch (102 mm) connector shall be permitted. Chimney Liner Diameter. The total input to the common vent is Btu/h (40 kw). Using the Common Vent Capacity portion of Table (7), read down the total Vent Height (H) column to 30 feet (9144 mm) and across this row to find the smallest vent diameter in the FAN + NAT column that has a Btu/h rating exceeding Btu/h (40 kw). The 4 inch (102 mm) common vent has a capacity of Btu/h (40.4 kw). Reducing the maximum capacity by 20 percent results in a maximum capacity for a 4 inch (102 mm) corrugated liner of Btu/h (32 kw), less than the total input of Btu/h (40 kw). So a larger liner is needed. The 5 inch (127 mm) common vent capacity listed in Table (7) is Btu/h (62 kw), and after reducing by 20 percent is Btu/h (49.2 kw). Therefore, a 5 inch (127 mm) corrugated metal liner shall be used in this example. Single Wall Connectors. Once it has been established that relining the chimney is necessary, Type B double-wall vent connectors are not specifically required. This example shall be permitted to be redone using Table (8) for single-wall vent connectors. For this case, the vent connector and liner diameters would be the same as found for Type B double-wall connectors. F 3.0 Example of Combination Indoor and Outdoor Combustion Air Opening. Determine the required combination of indoor and outdoor combustion air opening sizes for the following appliance installation example. Example Installation: A fan-assisted furnace and a draft hoodequipped water heater with the following inputs are located in a 15 foot (4572 mm) by 30 foot (9144 mm) basement with an 8 foot (2438 mm) ceiling. No additional indoor spaces shall be used to help meet the appliance combustion air needs. Fan-Assisted Furnace Input: Btu/h (29 kw) Draft Hood-Equipped Water Heater Input: Btu/h (11.7 kw) (1) Determine the total available room volume. Equipment room volume. 15 feet (4572 mm) by 30 feet (9144 mm) with an 8 foot (2438 mm) ceiling = 3600 cubic feet ( m 3 ) (2) Determine the total required volume. The standard method to determine combustion air shall be used to calculate the required volume. The combined input for the appliances located in the basement is calculated as follows: Btu/h (29 kw) Btu/h (11.7 kw) = Btu/h (41 kw) The standard method requires that the required volume be determined based on 50 cubic feet per 1000 Btu/h (4.83 m 3 /kw). Using Table F 3.0 the required volume for a Btu/h (41 kw) water heater is 7000 cubic feet ( m 3 ). Conclusion: Indoor volume is insufficient to supply combustion air since the total of 3600 cubic feet ( m 3 ) does not meet the required volume of 7000 cubic feet ( m 3 ). Therefore, additional combustion air shall be provided from the outdoors. (3) Determine ratio of the available volume to the required volume cubic feet 7000 cubic feet = 0.51 (4) Determine the reduction factor to be used to reduce the full outdoor air opening size to the minimum required based on ratio of indoor spaces (from Step 3) = 0.49 (5) Determine the single outdoor combustion air opening size as if combustion air is to come from outdoors. In this example, the combustion air opening directly communicates with the outdoors Btu/h 3000 British thermal units per square inch (Btu/in 2 ) = 47 square inches (0.03m 2 ) 2013 CALIFORNIA MECHANICAL CODE 443

12 (6) Determine the minimum outdoor combustion air opening area. Outdoor opening area = 0.49 (from Step 4) x 47 square inches (0.03m 2 ) = 23 square inches (0.01m 2 ) Section (3) requires the minimum dimension of the air opening shall be not less than 3 inches (76 mm). TABLE F 3.0 STANDARD METHOD: REQUIRED VOLUME, ALL APPLIANCES APPLIANCE INPUT (Btu/h) REQUIRED VOLUME (cubic feet) For SI units: 1000 British thermal units per hour = kw, 1 cubic foot = m CALIFORNIA MECHANICAL CODE