SJVUAPCD 4902 - 1 3/19/2009

RULE 4902 RESIDENTIAL WATER HEATERS (Adopted June 17, 1993; Amended March 

19, 2009) 

1.0 Purpose 

 The purpose of this rule is to limit oxides of nitrogen emissions from residential water 

heaters. 

2.0 Applicability 

 This rule applies to manufacturers, distributors, retailers, and installers of PUC quality 

natural gas-fired residential water heaters with heat input rates less than or equal to 

75,000 Btu/hr. 

3.0 Definitions 

3.1 Air Pollution Control Officer (APCO): As defined in Rule 1020 (Definitions). 

3.2 California Public Utility Commission (PUC) Quality Natural Gas: Any gaseous 

fuel, gas-containing fuel where the sulfur content is no more than one-fourth 

(0.25) grain of hydrogen sulfide per one hundred (100) standard cubic feet and 

no more than five (5) grains of total sulfur per one hundred (100) standard cubic 

feet. PUC quality natural gas also means high methane gas of at least 80% 

methane by volume. 

 3.3 Heat Output: The product obtained by multiplying the recovery efficiency, as 

defined by Section 6.1.3 of the Code of Federal Regulation, Title 10, Part 430, 

Subpart B, Appendix E, by the input rating of the water heater. 

 3.4 Input Rating: The amount of energy a water heater consumes in one hour 

(Btu/Hour). 

3.5 Instantaneous Water Heater: A water heater that heats water only when it flows 

through a heat exchanger. 

3.6 Mobile Home Water Heater: A closed vessel manufactured exclusively for 

mobile home use in which water is heated by combustion of gaseous fuel and is 

withdrawn for use external to the vessel at pressures not exceeding 160 psig, 

including the apparatus by which heat is generated and all controls and devices 

necessary to prevent water temperatures from exceeding 210oF (99oC). 

3.7 Pool Heater: A water heater designed to heat a pool, hot tub, or spa. 
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3.8 Water Heater: A closed vessel, in which water is heated by the combustion of 

PUC quality natural gas and is withdrawn for use external to the vessel at 

pressures not exceeding 160 psig, including the apparatus by which heat is 

generated and all controls and devices necessary to prevent water temperatures 

from exceeding 210°F (99oC). 

4.0 Exemptions 

 4.1 PUC quality natural gas-fired water heaters with rated heat input of greater than 

75,000 Btu per hour. 

 4.2 Water heaters using fuels other than PUC quality natural gas. 

4.3 Pool heaters. On and after January 1, 2010, pool heaters shall comply with all 

applicable requirements of this rule. 

 4.4 Water heaters used exclusively in recreational vehicles. 

5.0 Requirements 

5.1 On and before December 31, 2009, no person shall sell, install or offer for sale 

within the District any PUC quality natural gas-fired water heater manufactured 

after December 17, 1993, except for mobile home water heaters subject to 

Section 5.2, unless the water heater is certified pursuant to Section 6.1 to a NOx 

emission level of less than or equal to 40 nanograms of nitrogen oxides 

(calculated as NO2) per Joule of heat output. 

5.2 No person shall manufacture for sale, distribute, sell, offer for sale, or install 

within the District any PUC quality natural gas-fired mobile home water heater 

unless the water heater is certified pursuant to Section 6.1 to a NOx emission 

level of less than or equal to 40 nanograms of NOx (calculated as NO2) per joule 

of heat output. 

5.3 On and after January 1, 2010, no person shall manufacture for sale, distribute, 

sell, offer for sale, or install within the District any PUC quality natural gasfired pool heater unless the water heater is certified pursuant to Section 6.1 to a 

NOx emission level of less than or equal to 40 nanograms of NOx (calculated as 

NO2) per joule of heat output. 

5.4 On and after January 1, 2010, no person shall manufacture for sale, distribute, 

sell, offer for sale, or install within the District any PUC quality natural gasfired water heater, excluding mobile home water heaters, instantaneous water 

heaters, and pool heaters, unless the water heater is certified pursuant to Section 
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6.1 to a NOx emission level of less than or equal to 10 nanograms of NOx 

(calculated as NO2) per joule of heat output. 

5.5 On and after January 1, 2012, no person shall manufacture for sale, distribute, 

sell, offer for sale, or install within the District any PUC quality natural gasfired instantaneous water heater unless the water heater is certified pursuant to 

Section 6.1 to a NOx emission level of less than or equal to 14 nanograms of 

NOx (calculated as NO2) per joule of heat output. 

6.0 Administrative Requirements 

 6.1 Certification 

 6.1.1 Each water heater undergoing testing shall be operated in accordance 

with Section 2.4 of American National Standards ANSI Z21.10.1-1990, 

Z21.10.3-2004, or Z21.56-2006, as applicable, at normal test pressure, 

input rates, and with a five-foot exhaust stack installed during the 

nitrogen oxides emission tests. 

 6.1.2 The manufacturer shall demonstrate that each water heater model subject 

to the requirements of Section 5.0 has been tested in accordance with 

EPA Reference Test Method 7E, 40 CFR Part 60, Appendix A. 

 6.1.3 The following formula shall be used to calculate the emissions of NOx in 

nanograms of NOx per Joule of heat output: 

N = (4.566 x 104 x P x U)/(H x C x E) 

 Where: 

 N = NOX emission rate in nanograms of NOX emitted 

per Joule of heat output 

 4.566 x 104

 = unit conversion factor (ppm to nanograms and Btu 

to Joules) 

 P = Concentration of NOX in the flue gas in parts per 

million (volume) 

 U = Dry volume percent of CO2 in flue gas necessary 

for stoichiometric combustion 

 H = Gross heating value of the gas, Btu/Cu ft (at 60°F 

and 30" Hg) 

 C = Dry volume percent of CO2 in flue gas 

 E = Recovery efficiency, percentage, as defined in 

Section 6.1.3 of the Code of Federal Regulation, 

Title 10, Part 430, Subpart B, Appendix E 
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 6.1.4 The manufacturer may submit to the APCO an approved South Coast Air 

Quality Management District Rule 1121 (Control of Nitrogen Oxides 

From Residential Type, Natural Gas-Fired Water Heaters), Ventura 

County Air Pollution Control District Rule 74.11 (Natural Gas-Fired 

Residential Water Heaters – Control of NOx), or Bay Area Air Quality 

Management District Regulation 9 Rule 6 (Nitrogen Oxides Emissions 

from Natural Gas-Fired Boilers and Water Heaters) certification in lieu 

of conducting duplicative certification tests pursuant to Section 6.1. 

 6.1.5 Upon request of the APCO, each manufacturer shall submit to the APCO 

a statement certifying the water heaters subject to this rule are in 

compliance with the provisions of Section 5.0. The statement shall be 

signed, dated and shall attest to the accuracy of all information. The 

statement shall include: 

 

6.1.5.1 Name and address of manufacturer, 

6.1.5.2 Brand name, 

6.1.5.3 Model number, as it appears on the water heater rating plate, 

and 

6.1.5.4 Heat input rating, Btu/hr. 

 6.2 For units subject to Section 5.0, the manufacturer shall display the following on 

the shipping carton and rating plate of each unit: 

6.2.1 the model number, 

6.2.2 the date of manufacture, and 

6.2.3 the certification status.