Already a subscriber? 
MADCAD.com Free Trial
Sign up for a 3 day free trial to explore the MADCAD.com interface, PLUS access the
2009 International Building Code to see how it all works.
If you like to setup a quick demo, let us know at support@madcad.com
or +1 800.798.9296 and we will be happy to schedule a webinar for you.
Security check
Please login to your personal account to use this feature.
Please login to your authorized staff account to use this feature.
Are you sure you want to empty the cart?
ASHRAE Standard 118.2-2022 -- Method of Testing for Rating Residential Water Heaters and Residential-Duty Commercial Water Heaters (ANSI Approved), 2022
- ANSI/ASHRAE Standard 118.2-2022 [Go to Page]
- CONTENTS
- FOREWORD
- 1. PURPOSE
- 2. SCOPE [Go to Page]
- 2.1 Electric heat-pump storage water heaters that
- 2.2 Electric instantaneous water heaters that
- 2.3 Electric storage water heaters that
- 2.4 Gas-fired heat-pump storage water heaters that
- 2.5 Gas-fired instantaneous water heaters that
- 2.6 Gas-fired storage water heaters that
- 2.7 Oil-fired instantaneous water heaters that
- 2.8 Oil-fired storage water heaters that
- 3. DEFINITIONS [Go to Page]
- 3.1 Symbol Usage. The following identity relationships are provided to help clarify the symbology used throughout this procedure:
- 4. TEST CONDITIONS [Go to Page]
- 4.1 Installation Requirements. Tests shall be performed with the water heater and instrumentation installed in accordance with Section 6 of this document.
- 4.2 Ambient Air Temperature. The ambient air temperature shall be maintained at the nominal ambient air temperature ±2.5°F (±1.4°C) on a continuous basis. For heat-pump water heaters, the dry bulb temperature shall be maintained at the nominal am...
- 4.3 Supply Water Temperature. The temperature of the water being supplied to the water heater shall be maintained at nominal inlet temperature ±2°F (±1.1°C) throughout the test.
- 4.4 Outlet Water Temperature. The temperature controllers of a storage-type water heater shall be set so that water is delivered at the nominal outlet temperature ±5°F (±2.8°C).
- 4.5 Set-Point Temperature. The temperature controller of instantaneous water heaters shall be set to deliver water at the nominal outlet temperature ±5°F (±2.8°C).
- 4.6 Supply Water Pressure. During the test when water is not being withdrawn, the supply pressure shall be maintained between 40 psig (275 kPa) and the maximum allowable pressure specified by the water-heater manufacturer.
- 4.7 Electrical and/or Fossil-Fuel Supply
- 5. INSTRUMENTATION [Go to Page]
- 5.1 Pressure Measurements
- 5.2 Temperature Measurement
- 5.3 Liquid Flow Rate Measurement
- 5.4 Electrical Energy
- 5.5 Fossil Fuels. The quantity of fuel used by the water heater shall be measured with an instrument and associated readout device that is accurate within ±1% of the reading.
- 5.6 Mass Measurements. For mass measurements greater than or equal to 10 lb (4.5 kg), a scale that is accurate within ±0.5% of the reading shall be used to make the measurement. For mass measurements less than 10 lb (4.5 kg), the scale shall provide...
- 5.7 Heating Value. The higher heating value of the natural gas, propane, or fuel oil shall be measured with an instrument and associated readout device that is accurate within ±1% of the reading. The heating values of natural gas and propane must be...
- 5.8 Time. The elapsed time measurements shall be measured with an instrument that is accurate within ±0.5 seconds per hour.
- 5.9 Volume. Volume measurements shall be measured with an accuracy of ±2% of the total volume.
- 5.10 Relative Humidity
- 6. INSTALLATION [Go to Page]
- 6.1 Water-Heater Mounting. A water heater designed to be free standing shall be placed on a 3⁄4 in. (2 cm) thick plywood platform supported by three 2 × 4 in. (5 × 10 cm) runners. If the water heater is not approved for installation on combustibl...
- 6.2 Water Supply. Connect the water heater to a water supply capable of delivering water at conditions as specified in Sections 4.3 and 4.6 and at flow rates specified in Section 7.5.
- 6.3 Water Inlet and Outlet Configuration. For free-standing water heaters that are taller than 36 in. (91.4 cm), inlet and outlet piping connections shall be configured in a manner consistent with Figure 1, 2, or 3. Inlet and outlet piping connection...
- 6.4 Fuel and/or Electrical Power and Energy Consumption. Install one or more instruments that measure, as appropriate, the quantity and rate of electrical energy and/or fossil-fuel consumption in accordance with Section 5.
- 6.5 Internal Storage-Tank Temperature Measurements. For water heaters with rated storage volumes greater than or equal to 20 gal (76 L), install six temperature measurement sensors inside the water heater tank with a vertical distance of at least 4 i...
- 6.6 Ambient Air Temperature Measurement. Install an ambient air temperature sensor at the vertical midpoint of the water heater and approximately 2 ft (610 mm) from the surface of the water heater. Shield the sensor against radiation.
- 6.7 Inlet and Outlet Water Temperature Measurements. Install temperature sensors in the cold-water inlet pipe and hot-water outlet pipe as shown in Figures 1 through 11, as applicable.
- 6.8 Flow Control. Install a valve or valves to provide flow as specified in Sections 7.3 and 7.4.
- 6.9 Flue Requirements
- 7. TEST PROCEDURES [Go to Page]
- 7.1 Operational Mode Selection. For water heaters that allow for multiple user-selected operational modes, all procedures specified in this test method shall be carried out with the water heater in the same operational mode (i.e., only one mode). Thi...
- 7.2 Water-Heater Preparation
- 7.3 Delivery Capacity Tests
- 7.4 Twenty-Four-Hour Simulated-Use Test
- 7.5 Draw Patterns. The draw patterns to be imposed during 24-hour simulated-use tests are to be specified by the entity requesting the test. Provided strictly for informative purposes, examples of these draw patterns are shown in Informative Appendix...
- 8. CALCULATION OF RESULTS [Go to Page]
- 8.1 First-Hour Rating. The first-hour rating (FHR) shall be computed using the following:
- 8.2 Maximum GPM (L/min) Rating. Compute the maximum gpm (L/min) rating, Fmax, as follows:
- 8.3 Uniform Energy Factor—Water Heaters with a Rated Storage Volume Greater than or Equal to 2.0 Gal (7.6 L)
- 8.4 Water Heaters with Rated Storage Volume Less than 2.0 Gal (7.6 L)
- 9. REFERENCES
- INFORMATIVE APPENDIX A: U.S. VALUES FOR TEST VARIABLES
- INFORMATIVE APPENDIX B: GAS HEATING VALUE CORRECTION FACTOR [Go to Page]
