Appendix J — COMBINATION OF INDOOR AND OUTDOOR COMBUSTION AND VENTILATION OPENING DESIGN

(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.)

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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APPENDIX J

COMBINATION OF INDOOR AND OUTDOOR COMBUSTION AND

VENTILATION OPENING DESIGN

The provisions contained in this appendix are not mandatory unless specifically adopted by a state agency, or referenced in (The content of this Appendix is based on Annex I of NFPA 54) 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 draft-hoodequipped 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:

volume:

3600 cubic feet = 0.51 7000 cubic feet

(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 through 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 be not less than 3 inches (76 mm).

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APPENDIX J any other purpose or distributed to any other persons or parti es.

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

[NFPA 54: TABLE A.9.3.2.1]

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CALIFORNIA PLUMBING CODE – MATRIX ADOPTION TABLE