Appendix J — COMBINATION OF INDOOR AND OUTDOOR COMBUSTION

(Matrix Adoption Tables are non-regulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)

Adopting Agency	BSC	BSC- CG	SFM	HCD			DSA			OSHPD						BSCC	DPH	AGR	DWR	CEC	CA	SL	SLC
Adopting Agency	BSC	BSC- CG	SFM	1	2	1-AC	AC	SS	SS/CC	1	1R	2	3	4	5	5	5	5	5	5	5	5	5
Adopt Entire Chapter	X
Adopt Entire Chapter as amended (amended sections listed below)
Adopt only those sections that are listed below
Chapter/Section

This state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.0.

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476 2022 CALIFORNIA PLUMBING CODE

APPENDIX J

COMBINATION OF INDOOR AND OUTDOOR COMBUSTION AND

VENTILATION OPENING DESIGN

(The content of this Appendix is based on Annex I of NFPA 54)

The provisions contained in this appendix are not mandatory unless specifically adopted by a state agency, or referenced in the adopting ordinance.

J 101.0 General. J 101.1 Applicability. This appendix provides general guidelines for the sizing of combination indoor and outdoor combustion and ventilation air openings.

J 101.2 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 drafthood-equipped water heater with the following inputs are located in a 15 foot by 30 foot (4572 mm by 9144 mm) basement with an 8 foot (2438 mm) ceiling. No additional indoor spaces can be used to help meet the appliance combustion air needs.

Fan-Assisted Furnace Input: 100 000 British thermal units per hour (Btu/h) (29 kW) Draft Hood-Equipped Water Heater Input: 40 000 Btu/h (11.7 kW)

Solution: (1) Determine the total available room volume. Appliance

room volume: 15 feet by 30 feet (4572 mm by 9144 mm) with an 8 foot (2438 mm) ceiling = 3600 cubic feet (101.94 m ³ )

(2) Determine the total required volume. The standard

method to determine combustion air is used to calculate the required volume. The combined input for the appliances located in the basement is calculated as follows:

100 000 Btu/h (29 kW) + 40 000 Btu/h (11.7 kW) = 140 000 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 J 101.2, the required volume for a 140 000 Btu/h (41 kW) water heater is 7000 cubic feet (198.22 m ³ ).

Conclusion: The indoor volume is insufficient to supply combustion air since the total of 3600 cubic feet (101.94 m ³ ) does not meet the required volume of 7000 cubic feet (198.22 m ³ ).

Therefore, additional combustion air shall be provided from the outdoors. (3) Determine ratio of the available volume to the required

volume:

(4) Determine the reduction factor to be used to reduce the

full outdoor air opening size to the minimum required based on the ratio of indoor spaces:

1.00 – 0.51 (from Step 3) = 0.49

(5) Determine the single outdoor combustion air opening

size as though all combustion air is to come from outdoors. In this example, the combustion air opening directly communicates with the outdoors:

140 000 Btu/h = 47 square inches (0.03 m ² ) 3000 British thermal units per square inch (Btu/in ² )

(6) Determine the minimum outdoor combustion air open ing area: Outdoor opening area = 0.49 (from Step 4) x 47 square inches (0.03 m ² ) = 23 square inches (0.01 m ² )

Section 506.5.3(3) requires the minimum dimension of the air opening should not be less than 3 inches (76 mm).

2022 CALIFORNIA PLUMBING CODE 477

APPENDIX J

TABLE J 101.2 STANDARD METHOD: REQUIRED VOLUME, ALL APPLIANCES*

[NFPA 54: TABLE A.9.3.2.1]

APPLIANCE INPUT (Btu/h)	REQUIRED VOLUME (cubic feet)
5000	250
10 000	500
15 000	750
20 000	1000
25 000	1250
30 000	1500
35 000	1750
40 000	2000
45 000	2250
50 000	2500
55 000	2750
60 000	3000
65 000	3250
70 000	3500
75 000	3750
80 000	4000
85 000	4250
90 000	4500
95 000	4750
100 000	5000
105 000	5250
110 000	5500
115 000	5750
120 000	6000
125 000	6250
130 000	6500
135 000	6750
140 000	7000
145 000	7250
150 000	7500
160 000	8000
170 000	8500
180 000	9000
190 000	9500
200 000	10 000
210 000	10 500
220 000	11 000
230 000	11 500
240 000	12 000
250 000	12 500
260 000	13 000
270 000	13 500
280 000	14 000
290 000	14 500
300 000	15 000

478 2022 CALIFORNIA PLUMBING CODE

CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE