SACAQMD RULE 414 NATURAL GAS-FIRED WATER HEATERS

LAST REVISED 08/01/96

RULE 414

NATURAL GAS-FIRED WATER HEATERS

Adopted 08-01-96

INDEX

100 GENERAL

101 PURPOSE 

102 APPLICABILITY 

110 EXEMPTION, LARGE WATER HEATERS 

111 EXEMPTION, WATER HEATERS IN RECREATIONAL VEHICLES 

112 EXEMPTION, WATER HEATERS IN SWIMMING POOLS AND HOT TUBS 

113 EXEMPTION, WATER HEATERS USING A FUEL OTHER THAN NATURAL GAS 

200 DEFINITIONS

201 BRITISH THERMAL UNIT 

202 HEAT INPUT 

203 HEAT OUTPUT 

204 MOBILE HOME WATER HEATER 

205 NATURAL GAS 

206 NATURAL GAS-FIRED WATER HEATER 

207 RATED HEAT INPUT CAPACITY 

208 RECREATIONAL VEHICLE 

300 STANDARDS
301 NITROGEN OXIDES EMISSION LIMIT

400 ADMINISTRATIVE REQUIREMENTS

401 COMPLIANCE SCHEDULE 

402 CERTIFICATION REQUIREMENT 

403 MANUFACTURERS' LABELING REQUIREMENT 

404 CALCULATION FOR DETERMINATION OF HEAT OUTPUT 

405 CALCULATION FOR DETERMINATION OF STORAGE TANK CAPACITY 

500 MONITORING AND RECORD KEEPING

501 TESTING PROCEDURE 

502 DURATION OF RECORDS 

100 GENERAL

101 PURPOSE: To limit the emission of nitrogen oxides (NOx) from natural gas-fired water heaters. 

102 APPLICABILITY: This rule shall apply to any person who manufactures, distributes, offers for 

sale, sells, or installs any natural gas-fired water heater with a rated heat input capacity less than 75,000 

British thermal units per hour (Btu/hr), for use in this District. 

110 EXEMPTION, LARGE WATER HEATERS: This rule shall not apply to water heaters with a 

rated heat input of 75,000 Btu/hr or greater. 

111 EXEMPTION, WATER HEATERS IN RECREATIONAL VEHICLES: This rule shall not 

apply to water heaters used in recreational vehicles. 

112 EXEMPTION, WATER HEATERS IN SWIMMING POOLS AND HOT TUBS: This rule 

shall not apply to water heaters used exclusively to heat swimming pools and hot tubs. 

113 EXEMPTION, WATER HEATERS USING A FUEL OTHER THAN NATURAL GAS: This 

rule shall not apply to water heaters using any fuel other than natural gas. 

200 DEFINITIONS

201 BRITISH THERMAL UNIT (Btu): The amount of heat required to raise the temperature of one 

pound of water from 59·F to 60·F at one atmosphere. 

202 HEAT INPUT: The actual amount of heat released by natural gas burned in a water heater.
203 HEAT OUTPUT: The product Ho as defined in Section 404. 

204 MOBILE HOME WATER HEATER:A natural gas-fired water heater manufactured exclusively 

for mobile home use. 

205 NATURAL GAS: A mixture of gaseous hydrocarbons containing at least 80 percent methane by 

volume as determined according to American Standard Test Method (ASTM) D1945-64. 

206 NATURAL GAS-FIRED WATER HEATER: A closed vessel in which water is heated by the 

combustion of 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 (99·C). 

207 RATED HEAT INPUT CAPACITY: The heat input capacity specified on the nameplate of the 

combustion unit. If the combustion unit has been altered or modified such that its maximum heat input is 

different than the heat input capacity specified on the nameplate, the new maximum heat input shall be 

considered as the rated heat input capacity. 

208 RECREATIONAL VEHICLE: A motor home, travel trailer, truck camper, or camping trailer, 

with or without motive power, designed for human habitation for recreational, emergency, or other 

occupancy, which meets all of the following criteria: 1) contains less than 320 square feet of internal 

living room area, excluding built-in equipment, including, but not limited to wardrobe, closets, cabinets, 

kitchen units or fixtures, and bath or toilet rooms; 2) it contains 400 square feet or less of gross area 

measured at maximum horizontal projections; 3) it is built on a single chassis; and 4)it is either self 

propelled, truck mounted, or permanently towable on the highways without a permit. 

300 STANDARDS

301 NITROGEN OXIDES EMISSION LIMIT: A person shall only distribute, offer for sale, sell, or 

install within the Sacramento Metropolitan Air Quality Management District either of the following: 

301.1 A natural gas-fired water heater that emits less than or equal to 40 nanograms of nitrogen 

oxides (calculated as NO2) per joule (93 pounds per billion Btu) of heat output; and is certified in 

accordance with Section 402. 

301.2 A mobile home natural gas-fired water heater that emits less than or equal to 50 nanograms 

of nitrogen oxides (calculated as NO2) per joule (116 pounds per billion Btu) of heat output; and 

is certified in accordance with Section 402. 

400 ADMINISTRATIVE REQUIREMENTS

401 COMPLIANCE SCHEDULE: Effective March 1, 1997, no person shall distribute, offer for sale, 

sell, or install any natural gas-fired water heater which does not comply with the requirements of Section 

300. 

402 CERTIFICATION REQUIREMENT: 

402.1 A manufacturer of any natural gas fired water heater subject to Section 300 shall submit to 

the Air Pollution Control Officer (APCO) a statement certifying that water heaters manufactured 

by it and subject to this rule are in compliance with the provisions of Section 300 at least 30 days 
prior to sale. The statement shall be signed, dated, and shall attest to the accuracy of all 

information. The statement shall include the brand name, model number, the input rating as it 

appears on the water heater rating plate, and test results in accordance with Section 501; or 

402.2 A manufacturer shall submit to this District an approved South Coast Air Quality 

Management District certification. Any model of natural gas-fired water heater certified as 

complying with the South Coast Air Quality Management District's Rule 1121 prior to July 1, 

1995, need not be recertified to the test protocol specified in Section 501 until such time as 

required by the South Coast Air Quality Management District. 

403 MANUFACTURERS' LABELING REQUIREMENT: A manufacturer shall display the model 

number of the water heater complying with Section 300 on the shipping carton and on the rating plate of 

each water heater unit. The manufacturer shall also display the certification status on the shipping carton 

and on the water heater. 

404 CALCULATION FOR DETERMINATION OF HEAT OUTPUT: Heat output is computed 

using the following equation, as contained in the Protocol: 

Ho= MCpi(Tdel - Tin) + VstDnCp2(Tmax - To)

Where: 

Ho= heat output in British thermal units.

M = mass of the water withdrawn in pounds. 

Cpi= specific heat of water at the average temperature (Tdel + Tin)/2, British thermal 

units/pound oF.

Tdel = average delivery temperature oF.

Tin= average inlet temperature oF.

Vst= storage tank capacity in gallons, as determined in Section 405.

Dn= density of water at the average temperature (Tmax + To)/2 in pounds/gallon.

Cp2= specific heat of water at the average temperature (Tmax + T

o

)/2 in British 

thermal units/pound oF.

T

max

= maximum mean tank temperature recorded after cutout following the test draw

oF.

To

= the maximum mean tank temperature recorded prior to the test draw oF. 
405 CALCULATION FOR DETERMINATION OF STORAGE TANK CAPACITY: Storage tank 

capacity is computed by the following equation: 

Vst = (Wf- Wt)/Ds

Where : 

Vst = storage capacity of the water heater in gallons.

Wf = weight of the water heater completely filled with water in pounds.

Wt = weight of the empty water heater in pounds.

Ds= density of water at the appropriate temperature in pounds/gallon.

500 MONITORING AND RECORD KEEPING

501 TESTING PROCEDURE: Any natural gas-fired water heater distributed, offered for sale, sold, or 

installed within the District shall be tested in accordance with the South Coast Air Quality Management 

District Protocol: Nitrogen Oxides Emission Compliance Testing for Natural Gas-Fired Water Heaters 

and Small Boilers, January 1995. 

502 DURATION OF RECORDS: A manufacturer shall keep test reports and certification records for 

as long as the water heater model is offered for sale or sold in the District, or for three calendar years 

after manufacture, whichever is longer. These records shall be made available to the Air Pollution 

Control Officer upon request.