404.1 Service Water Heating Equipment Efficiency. Equipment must satisfy the minimum performance efficiency specified in Table 404.1 when tested in accordance with RS-37, RS-38, or RS-39 (incorporated by reference, see §434.701). Omission of equipment from Table 404.1 shall not preclude the use of such equipment. Service water heating equipment used to provide additional function of space heating as part of a combination (integrated) system shall satisfy all stated requirements for the service water heating equipment. All gas-fired storage water heaters that are not equipped with a flue damper and use indoor air for combustion or draft hood dilution and that are installed in a conditioned space, shall be equipped with a vent damper listed in accordance with RS-42 (incorporated by reference, see §434.701). Unless the water heater has an available electrical supply, the installation of such a vent damper shall not require an electrical connection.
Table 404.1—Minimum Performance of Water Heating Equipment
| Category | Type | Fuel | Input rating | VT | Input to VT ratio Btuh/gal | Test Methoda | Energy factor | Thermal efficiency Et% | Standby loss %/HR |
|---|---|---|---|---|---|---|---|---|---|
| NAECA | all | electric | 12 kW | allc | DOE Test | 0.93-0.00132V | |||
| Covered | storage | gas | 75,000 Btuh | allc | Procedure 10 | 0.62-0.0019V | |||
| Water | instantaneous | gas | 200,000 | all | CFR part 430 | 0.62-0.0019V | |||
| Heating | storage | oil | Btuhc | all | 430 | 0.59-0.0019V | |||
| Equipmentb | instantaneous | oil | 105,000 Btuh |
all | Appendix E | 0.59-0.0019V | |||
| pool heater | gas/oil | 210,000 Btuh | all | ANSI Z21.56 | 78 | ||||
| all | (RS-38)* | ||||||||
| Other Water | storage | electric | all | all | ANSI | ||||
| Heating | Z21.10.3 | 78 | .030 + 27/VT | ||||||
| Equipmentd | storage/ instantaneous |
gas/oil | 155m999 Btuh | all | <4,000 | (RS-39)* | 78 | 1.3 + 114//VT | |
| all | <4,000 | 80 | 1.3 + 95/VT | ||||||
| >155,000 Btuh | <10 | 4,000 | 77 | ||||||
| 10 | 4,000 | 2.3 + 67/VT | |||||||
| Unfired Storage Tanks |
all | 6.5 Btuh/ft2 |
aFor detailed references see subpart E.
bConsistent with National Appliance Energy Conservation Act (NAECA) of 1987.
cDOE Test Procedures apply to electric and gas storage water heaters with rated volumes 20 gallons and gas instantaneous water heaters with input ratings of 50,000 to 200,000 Btuh.
dAll except those water heaters covered by NAECA.
*Incorporated by reference, see §434.701.
404.1.1 Testing Electric and Oil Storage Water Heaters for Standby Loss.
(a) When testing an electric storage water heater, the procedures of Z21.10.3-1990 (RS-39, incorporated by reference, see §434.701), Section 2.9, shall be used. The electrical supply voltage shall be maintained with ±1% of the center of the voltage range specified on the water heater nameplate. Also, when needed for calculations, the thermal efficiency (Et) shall be 98%. When testing an oil-fired water heater, the procedures of Z21.10.3-1990 (RS-39 incorporated by reference, see §434.701), Sections 2.8 and 2.9, shall be used.
(b) The following modifications shall be made: A vertical length of flue pipe shall be connected to the flue gas outlet of sufficient height to establish the minimum draft specified in the manufacturer's installation instructions. All measurements of oil consumption shall be taken by instruments with an accuracy of ±1% or better. The burner rate shall be adjusted to achieve an hourly Btu input rate within ±2% of the manufacturer's specified input rate with the CO2 reading as specified by the manufacturer with smoke no greater than 1 and the fuel pump pressure within ±1% of the manufacturer's specification.
404.1.2 Unfired Storage Tanks. The heat loss of the tank surface area Btu/(h·ft2) shall be based on an 80 °F water-air temperature difference.
404.1.3 Storage Volume Symbols in Table 404.1. The symbol “V” is the rated storage volume in gallons as specified by the manufacturer. The symbol “VT” is the storage volume in gallons as measured during the test to determine the standby loss. VT may differ from V, but it is within tolerances allowed by the applicable Z21 and Underwriters Laboratories standards. Accordingly, for the purpose of estimating the standby loss requirement using the rated volume shown on the rating plate, VT should be considered as no less than 0.95V for gas and oil water heaters and no less than 0.90V for electric water heaters.
404.1.4 Electric Water Heaters. In applications where water temperatures not greater than 145 °F are required, an economic evaluation shall be made on the potential benefit of using an electric heat pump water heater(s) instead of an electric resistance water heater(s). The analysis shall compare the extra installed costs of the heat pump unit with the benefits in reduced energy costs (less increased maintenance costs) over the estimated service life of the heat pump water heater. Exceptions are as follows: Electric water heaters used in conjunction with site-recovered or site-solar energy sources that provide 50% or more of the water heating load or off-peak heating with thermal storage.
404.2 Service Hot Water Piping Insulation. Circulating system piping and noncirculating systems without heat traps, the first eight feet of outlet piping from a constant-temperature noncirculating storage system, and the inlet pipe between the storage tank and a heat trap in a noncirculating storage system shall meet the provisions of subsection 403.2.9.
404.2.1 Vertical risers serving storage water heaters not having an integral heat trap and serving a noncirculating system shall have heat traps on both the inlet and outlet piping as close as practical to the water heater.
404.3 Service Water Heating System Controls. Temperature controls that allow for storage temperature adjustment from 110 °F to a temperature compatible with the intended use shall be provided in systems serving residential dwelling units and from 90 °F for other systems. When designed to maintain usage temperatures in hot water pipes, such as circulating hot water systems or heat trace, the system shall be equipped with automatic time switches or other controls that can be set to turn off the system.
404.3.1 The outlet temperature of lavatory faucets in public facility restrooms shall be limited to 110 °F.
404.4 Water Conservation. Showerheads and lavatory faucets must meet the requirements of 10 CFR 430.32 (o)-(p).
404.4.1 Lavatory faucets in public facility restrooms shall be equipped with a foot switch, occupancy sensor, or similar device or, in other than lavatories for physically handicapped persons, limit water delivery to 0.25 gal/cycle.
404.5 Swimming Pools. All pool heaters shall be equipped with a readily accessible on-off switch.
404.5.1 Time switches shall be installed on electric heaters and pumps. Exceptions are as follows:
(a) Pumps required to operate solar or heat recovery pool heating systems.
(b) Where public health requirements require 24-hour pump operation.
404.5.2 Heated swimming pools shall be equipped with pool covers. Exception: When over 70% of the annual energy for heating is obtained from a site-recovered or site-solar energy source.
404.6 Combined Service Water Heating and Space Heating Equipment. A single piece of equipment shall not be used to provide both space heating and service water heating. Exceptions are as follows:
(a) The energy input or storage volume of the combined boiler or water heater is less than twice the energy input or storage volume of the smaller of the separate boilers or water heaters otherwise required or
(b) The input to the combined boiler is less than 150,000 Btuh.
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