2.1. Placement of Water Heater. A water heater for installation on combustible floors must be placed on a 3⁄4-inch plywood platform supported by three 2 x 4-inch runners. If the water heater is for installation on noncombustible floors, suitable noncombustible material must be placed on the platform. When the use of the platform for a large water heater is not practical, the water heater may be placed on any suitable flooring. A wall-mounted water heater must be mounted on a simulated wall section.

2.2. Installation of Temperature Sensors. Inlet and outlet water piping must be turned vertically downward from the connections on the water heater so as to form heat traps. Temperature sensors for measuring supply and outlet water temperatures must be installed upstream from the inlet heat trap piping and downstream from the outlet heat trap piping, respectively, in accordance with Figure 2.1, 2.2, or 2.3 (as applicable based on the location of inlet and outlet piping connections) of this section.

The water heater must meet the requirements shown in Figure 2.1, 2.2, or 2.3 (as applicable) at all times during the conduct of the thermal efficiency and standby loss tests. Any factory-supplied heat traps must be installed per the installation instructions while ensuring the requirements in Figure 2.1, 2.2, or 2.3 are met. All dimensions specified in Figure 2.1, 2.2, and 2.3 and in this section are measured from the outer surface of the pipes and water heater outer casing (as applicable).

2.3 Installation of Temperature Sensors for Measurement of Mean Tank Temperature. Install temperature sensors inside the tank for measurement of mean tank temperature according to the instructions in paragraph f of Annex E.1 of ANSI Z21.10.3-2015 (incorporated by reference; see § 431.105). Calculate the mean tank temperature as the average of the six installed temperature sensors.

2.4. Piping Insulation. Insulate all water piping external to the water heater jacket, including heat traps and piping that are installed by the manufacturer or shipped with the unit, for at least 4 ft of piping length from the connection at the appliance, with material having an R-value not less than 4 °F·ft²·h/Btu. Ensure that the insulation does not contact any appliance surface except at the location where the pipe connections penetrate the appliance jacket or enclosure.

2.5. Temperature and Pressure Relief Valve Insulation. If the manufacturer has not provided a temperature and pressure relief valve, one shall be installed and insulated as specified in section 2.4 of this appendix.

2.6. Vent Requirements. Follow the requirements for venting arrangements specified in paragraph c of Annex E.1 of ANSI Z21.10.3-2015 (incorporated by reference; see § 431.105).

2.7. Energy Consumption. Install equipment that determines, within ± 1 percent:

3.1. Water Supply

3.2. Gas Pressure for Gas-Fired Equipment. The supply gas pressure must be within the range specified by the manufacturer on the nameplate of the unit being tested. The difference between the outlet pressure of the gas appliance pressure regulator and the value specified by the manufacturer on the nameplate of the unit being tested must not exceed the greater of: ± 10 percent of the nameplate value or ± 0.2 inches water column (in. w.c.). Obtain the higher heating value of the gas burned.

3.3. Ambient Room Temperature. During the soak-in period (as applicable), the steady-state verification period, the thermal efficiency test, and the standby loss test, maintain the ambient room temperature at 75 °F ± 10 °F at all times. Measure the ambient room temperature at 1-minute intervals during these periods, except for the soak-in period. Measure the ambient room temperature once before beginning the soak-in period, and ensure no actions are taken during the soak-in period that would cause the ambient room temperature to deviate from the allowable range. Measure the ambient room temperature at the vertical mid-point of the water heater and approximately 2 feet from the water heater jacket. Shield the sensor against radiation. Calculate the average ambient room temperature separately for the thermal efficiency test and standby loss test. During the thermal efficiency and standby loss tests, the ambient room temperature must not vary by more than ± 5.0 °F at any reading from the average ambient room temperature.

3.4. Test Air Temperature. During the steady-state verification period, the thermal efficiency test, and the standby loss test, the test air temperature must not vary by more than ± 5 °F from the ambient room temperature at any reading. Measure the test air temperature at 1-minute intervals during these periods and at a location within two feet of the air inlet of the water heater or the combustion air intake vent, as applicable. Shield the sensor against radiation. For units with multiple air inlets, measure the test air temperature at each air inlet, and maintain the specified tolerance on deviation from the ambient room temperature at each air inlet. For units without a dedicated air inlet, measure the test air temperature within two feet of any location on the water heater where combustion air is drawn.

3.5. Maximum Air Draft. During the steady-state verification period, the thermal efficiency test, and the standby loss test, the water heater must be located in an area protected from drafts of more than 50 ft/min. Prior to beginning the steady-state verification period and the standby loss test, measure the air draft within three feet of the jacket or enclosure of the water heater to ensure this condition is met. Ensure that no other changes that would increase the air draft are made to the test set-up or conditions during the conduct of the tests.

3.6. Setting the Tank Thermostat. Before starting the steady-state verification period (as applicable) or before the soak-in period (as applicable), the thermostat setting must first be obtained by starting with the water in the system at 70 °F ± 2 °F. Set the thermostat to ensure:

3.7. Additional Requirements for Oil-Fired Equipment.

3.8. Data Collection Intervals. Follow the data recording intervals specified in the following sections.

5. Thermal Efficiency Test. Before beginning the steady-state verification period, record the applicable parameters as specified in section 3.8.2 of this appendix. Begin drawing water from the unit by opening the main supply, and adjust the water flow rate to achieve an outlet water temperature of 70 °F ± 2 °F above supply water temperature. The thermal efficiency test shall be deemed complete when there is a continuous, one-hour-long period where the steady-state conditions specified in section 5.1 of this appendix have been met, as confirmed by consecutive readings of the relevant parameters recorded at 1-minute intervals (except for fuel input rate, which is determined at 10-minute intervals, as specified in section 5.4 of this appendix). During the one-hour-long period, the water heater must fire continuously at its full firing rate (i.e., no modulations or cut-outs) and no settings can be changed on the unit being tested at any time. The first 30 minutes of the one-hour-period where the steady-state conditions in section 5.1 of this appendix are met is the steady-state verification period. The final 30 minutes of the one-hour-period where the steady-state conditions in section 5.1 of this appendix are met is the thermal efficiency test. The last reading of the steady-state verification period must be the first reading of the thermal efficiency test (i.e., the thermal efficiency test starts immediately once the steady-state verification period ends).

1. Steady-State Conditions. The following conditions must be met at consecutive readings taken at 1-minute intervals (except for fuel input rate, for which measurements are taken at 10-minute intervals) to verify the water heater has achieved steady-state operation during the steady-state verification period and thermal efficiency test.

5.1.1. The water flow rate must be maintained within ± 0.25 gallons per minute (gpm) of the initial reading at the start of the steady-state verification period;

5.1.2. Outlet water temperature must be maintained at 70 °F ± 2 °F above supply water temperature;

5.1.3. Fuel input rate must be maintained within ± 2 percent of the rated input certified by the manufacturer;

5.1.4. The supply water temperature must be maintained within ± 0.50 °F of the initial reading at the start of the steady-state verification period; and

5.1.5. The rise between the supply and outlet water temperatures must be maintained within ± 0.50 °F of its initial value taken at the start of the steady-state verification period for units with rated input less than 500,000 Btu/h, and maintained within ± 1.00 °F of its initial value for units with rated input greater than or equal to 500,000 Btu/h.

5.2. Water Flow Measurement. Measure the total weight of water heated during the 30-minute thermal efficiency test with either a scale or a water flow meter. With either method, the error of measurement of weight of water heated must not exceed 1 percent of the weight of the total draw.

5. 3. Determination of Fuel Input Rate. During the steady-state verification period and the thermal efficiency test, record the fuel consumed at 10-minute intervals. Calculate the fuel input rate over each 10-minute period using the equations in section 5.4 of this appendix. The measured fuel input rates for these 10-minute periods must not vary by more than ± 2 percent between any two readings. Determine the overall fuel input rate using the fuel consumption for the entire duration of the thermal efficiency test.

5. 4. Fuel Input Rate Calculation. To calculate the fuel input rate, use the following equation:

Where,

Q = Fuel input rate, expressed in Btu/h

Q_s = Total fuel flow as metered, expressed in ft³ for gas-fired equipment and lb for oil-fired equipment

C_s = Correction applied to the heating value of a gas H, when it is metered at temperature and/or pressure conditions other than the standard conditions for which the value of H is based. Cs=1 for oil-fired equipment.

H = Higher heating value of fuel, expressed in Btu/ft³ for gas-fired equipment and Btu/lb for oil-fired equipment.

t = Duration of measurement of fuel consumption

5. 5. Thermal Efficiency Calculation. Thermal efficiency must be calculated using data from the 30-minute thermal efficiency test. Calculate thermal efficiency, E_t, using the following equation:

Where,

K = 1.004 Btu/lb· °F, the nominal specific heat of water at 105 °F

W = Total weight of water heated, expressed in lb

θ₁ = Average supply water temperature, expressed in °F

θ₂ = Average outlet water temperature, expressed in °F

Q = Total fuel flow as metered, expressed in ft³ for gas-fired equipment and lb for oil-fired equipment.

C_s = Correction applied to the heating value of a gas H, when it is metered at temperature and/or pressure conditions other than the standard conditions for which the value of H is based. C_s=1 for oil-fired equipment

H. = Higher heating value of the fuel, expressed in Btu/ft³ for gas-fired equipment and Btu/lb for oil-fired equipment.

E_c = Electrical consumption of the water heater and, when used, the test set-up recirculating pump, expressed in Btu

6.1. If no settings on the water heater have changed and the water heater has not been turned off since a previously run thermal efficiency or standby loss test, skip to section 6.3 of this appendix. Otherwise, conduct the soak-in period according to section 6.2 of this appendix.

6.2. Soak-In Period. Conduct a soak-in period, in which the water heater must sit without any draws taking place for at least 12 hours. Begin the soak-in period after setting the tank thermostat as specified in section 3.6 of this appendix, and maintain these thermostat settings throughout the soak-in period.

6.3. Begin the standby loss test at the first cut-out following the end of the soak-in period (if applicable); or at a cut-out following the previous thermal efficiency or standby loss test (if applicable). Allow the water heater to remain in standby mode. Do not change any settings on the water heater at any point until measurements for the standby loss test are finished. Begin recording the applicable parameters specified in section 3.8.3 of this appendix.

1. Placement of Water Heater. A water heater for installation on combustible floors must be placed on a 3⁄4-inch plywood platform supported by three 2 x 4-inch runners. If the water heater is for installation on noncombustible floors, suitable noncombustible material must be placed on the platform. When the use of the platform for a large water heater is not practical, the water heater may be placed on any suitable flooring. A wall-mounted water heater must be mounted on a simulated wall section.

2.

2. Test Configuration. If the instantaneous water heater or hot water supply boiler is not required to be tested using a recirculating loop, then set up the unit in accordance with Figures 2.1, 2.2, or 2.3 of this appendix (as applicable). If the unit is required to be tested using a recirculating loop, then set up the unit as per Figure 2.4 of this appendix.

2.2.1. If the instantaneous water heater or hot water supply boiler does not have any external piping, install an outlet water valve within 10 inches of piping length of the water heater jacket or enclosure. If the instantaneous water heater or hot water supply boiler includes external piping assembled at the manufacturer's premises prior to shipment, install water valves in the outlet piping within 5 inches of the end of the piping supplied with the unit.

2. 6. Vent Requirements. Follow the requirements for venting arrangements specified in paragraph c of Annex E.1 of ANSI Z21.10.3-2015 (incorporated by reference; see § 431.105).

2. Gas Pressure for Gas-Fired Equipment. The supply gas pressure must be within the range specified by the manufacturer on the nameplate of the unit being tested. The difference between the outlet pressure of the gas appliance pressure regulator and the value specified by the manufacturer on the nameplate of the unit being tested must not exceed the greater of: ± 10 percent of the nameplate value or ± 0.2 inches water column (in. w.c.). Obtain the higher heating value of the gas burned.

3.3. Ambient Room Temperature. Maintain the ambient room temperature at 75 °F ± 10 °F at all times during the steady-state verification period, the thermal efficiency test, and the standby loss test (as applicable). Measure the ambient room temperature at 1-minute intervals during these periods. Measure the ambient room temperature at the vertical mid-point of the water heater and approximately 2 feet from the water heater jacket or enclosure. Shield the sensor against radiation. Calculate the average ambient room temperature separately for the thermal efficiency test and the standby loss test. During the thermal efficiency and standby loss tests, the ambient room temperature must not vary by more than ± 5.0 °F at any reading from the average ambient room temperature.

3.4. Test Air Temperature. During the steady-state verification period, the thermal efficiency test, and the standby loss test (as applicable), the test air temperature must not vary by more than ± 5 °F from the ambient room temperature at any reading. Measure the test air temperature at 1-minute intervals during these periods and at a location within two feet of the air inlet of the water heater or the combustion air intake vent, as applicable. Shield the sensor against radiation. For units with multiple air inlets, measure the test air temperature at each air inlet, and maintain the specified tolerance on deviation from the ambient room temperature at each air inlet. For units without a dedicated air inlet, measure the test air temperature within two feet of any location on the water heater where combustion air is drawn.

3. 5. Maximum Air Draft. During the steady-state verification period, the thermal efficiency test, and the standby loss test (as applicable), the water heater must be located in an area protected from drafts of more than 50 ft/min. Prior to beginning the steady-state verification period and the standby loss test, measure the air draft within three feet of the jacket or enclosure of the water heater to ensure this condition is met. Ensure that no other changes that would increase the air draft are made to the test set-up or conditions during the conduct of the tests.

6. Thermal Efficiency Test. Before beginning the steady-state verification period, record the applicable parameters as specified in section 3.9.1 of this appendix. Begin drawing water from the unit by opening the main supply and outlet water valve, and adjust the water flow rate to achieve an outlet water temperature of 70 °F ± 2 °F above supply water temperature. The thermal efficiency test shall be deemed complete when there is a continuous, one-hour-long period where the steady-state conditions specified in section 6.1 of this appendix have been met, as confirmed by consecutive readings of the relevant parameters at 1-minute intervals (except for fuel input rate, which is determined at 10-minute intervals, as specified in section 5.1 of this appendix). During the one-hour-long period, the water heater must fire continuously at its full firing rate (i.e., no modulation or cut-outs) and no settings can be changed on the unit being tested at any time. The first 30 minutes of the one-hour-period where the steady-state conditions in section 6.1 of this appendix are met is the steady-state verification period. The final 30 minutes of the one-hour-period where the steady-state conditions in section 6.1 of this appendix are met is the thermal efficiency test. The last reading of the steady-state verification period must be the first reading of the thermal efficiency test (i.e., the thermal efficiency test starts immediately once the steady-state verification period ends).

6.3. Thermal Efficiency Calculation. Thermal efficiency must be calculated using data from the 30-minute thermal efficiency test. Calculate thermal efficiency, E_t, using the following equation:

Where:

K = 1.004 Btu/lb· °F, the nominal specific heat of water at 105 °F

W = Total weight of water heated, lb

θ₁ = Average supply water temperature, expressed in °F

θ₂ = Average outlet water temperature, expressed in °F

Q = Total fuel flow as metered, expressed in ft³ (gas) or lb (oil)

C_s = Correction applied to the heating value of a gas H, when it is metered at temperature and/or pressure conditions other than the standard conditions for which the value of H is based. C_s=1 for oil-fired equipment.

H = Higher heating value of the fuel, expressed in Btu/ft³ (gas) or Btu/lb (oil)

E_c = Electrical consumption of the water heater and, when used, the test set-up recirculating pump, expressed in Btu

7. Standby Loss Test. If the standby loss test is conducted immediately after a thermal efficiency test and no settings or conditions have been changed since the completion of the thermal efficiency test, then skip to section 7.2 or 7.3 of this appendix (as applicable). Otherwise, perform the steady-state verification in section 7.1 of this appendix. For thermostatically-activated instantaneous water heaters with an internal thermostat, use section 7.2 of this appendix to conduct the standby loss test, and for flow-activated and/or thermostatically-activated instantaneous water heaters with an external thermostat use section 7.3 of this appendix to conduct the standby loss test.

7.2. Thermostatically-Activated Instantaneous Water Heaters with an Internal Thermostat. For water heaters that will experience cut-in based on a temperature-activated control that is internal to the water heater, use the following steps to conduct the standby loss test.

7.2.1. Immediately after the thermal efficiency test or the steady-state verification period (as applicable), turn off the outlet water valve(s) (installed as per the provisions in section 2.2 of this appendix), and the water pump (if applicable) simultaneously and ensure that there is no flow of water through the water heater.

7. 2.2. After the first cut-out following the end of the thermal efficiency test or steady-state verification period (as applicable), allow the water heater to remain in standby mode. Do not change any settings on the water heater at any point until measurements for the standby loss test are finished. Begin recording the applicable parameters specified in section 3.9.2 of this appendix.

7. 2.3. At the second cut-out, record the time and ambient room temperature, and begin measuring the fuel and electricity consumption. Record the initial heat exchanger outlet water temperature (T_OHX) and initial ambient room temperature. For the remainder of the test, continue recording the applicable parameters specified in section 3.9.2 of this appendix.

7. 2.4. Stop the test after the first cut-out that occurs after 24 hours, or at 48 hours, whichever comes first.

7. 2.5. Immediately after conclusion of the standby loss test, record the total fuel flow and electrical energy consumption, the final ambient room temperature, the duration of the standby loss test, and if the test ends at 48 hours without a cut-out, the final heat exchanger outlet temperature, or if the test ends after a cut-out, the maximum heat exchanger outlet temperature that occurs after the cut-out. Calculate the average of the recorded values of the heat exchanger outlet water temperature and the ambient room temperature taken at each measurement interval, including the initial and final values.

7. 2.6. Standby Loss Calculation. To calculate the standby loss, follow the steps below:

7. 2.6.1. The standby loss expressed as a percentage (per hour) of the heat content of the stored water above room temperature must be calculated using the following equation:

Where:

ΔT₃ = Average value of the heat exchanger outlet water temperature (T_OHX) minus the average value of the ambient room temperature, expressed in °F

ΔT₄ = Final heat exchanger outlet water temperature (T_OHX) measured at the end of the test minus the initial heat exchanger outlet water temperature (T_OHX) measured at the start of the test, expressed in °F

K = 8.25 Btu/gallon· °F, the nominal specific heat of water

V_a = Volume of water contained in the water heater in gallons measured in accordance with section 4 of this appendix

E_t = Thermal efficiency of the water heater determined in accordance with section 6 of this appendix, expressed in %

E_c = Electrical energy consumed by the water heater during the duration of the test in Btu

T = Total duration of the test in hours

C_s = Correction applied to the heating value of a gas H, when it is metered at temperature and/or pressure conditions other than the standard conditions for which the value of H is based. C_s=1 for oil-fired equipment.

Q_s = Total fuel flow as metered, expressed in ft³ (gas) or lb (oil)

H = Higher heating value of gas or oil, expressed in Btu/ft³ (gas) or Btu/lb (oil)

S = Standby loss, the average hourly energy required to maintain the stored water temperature expressed as a percentage of the initial heat content of the stored water above room temperature

7.2.6.2. The standby loss expressed in Btu per hour must be calculated as follows:

SL (Btu per hour) = S (% per hour) × 8.25 (Btu/gal- °F) × Measured Volume (gal) × 70 ( °F).

Where, SL refers to the standby loss of the water heater, defined as the amount of energy required to maintain the stored water temperature expressed in Btu per hour.

7.3. Flow-Activated and Thermostatically-Activated Instantaneous Water Heaters with an External Thermostat. For water heaters that are either flow-activated or thermostatically-activated with an external thermostat, use the following steps to conduct the standby loss test.

7.3.1. Immediately after the thermal efficiency test or the steady-state verification period (as applicable), de-energize the primary control to end the call for heating. If the main burners do not cut out, then turn off the fuel supply.

7. 3.1.1. If the unit does not have an integral pump purge functionality, then turn off the outlet water valve and water pump at this time.

7.3.1.2. If the unit has an integral pump purge functionality, allow the pump purge operation to continue. After the pump purge operation is complete, immediately turn off the outlet water valve and water pump and continue recording the required parameters for the remainder of the test.

7.3.2. Recording Data

7.3.2.1. For units with pump purge functionality, record the initial heat exchanger outlet water temperature (T_OHX), and ambient room temperature when the main burner(s) cut-out or the fuel supply is turned off. After the pump purge operation is complete, record the time as t = 0 and the initial electricity meter reading. Continue to monitor and record the heat exchanger outlet water temperature (T_OHX) and time elapsed from the start of the test, and the electricity consumption as per the requirements in section 3.9.2 of this appendix.

7.3.2.2. For units not equipped with pump purge functionality, begin recording the measurements as per the requirements of section 3.9.2 of this appendix when the main burner(s) cut-out or the fuel supply is turned off. Specifically, record the time as t = 0, and record the initial heat exchanger outlet water temperature (T_OHX), ambient room temperature, and electricity meter readings. Continue to monitor and record the heat exchanger outlet water temperature (T_OHX) and the time elapsed from the start of the test as per the requirements in section 3.9.2 of this appendix.

7.3.3. Stopping Criteria. Stop the test when one of the following occurs:

7.3.3.1. The heat exchanger outlet water temperature (T_OHX) decreases by 35 °F from its value recorded immediately after the main burner(s) has cut-out, and the pump purge operation (if applicable) is complete; or

7.3.3.2. 24 hours have elapsed from the start of the test.

7.3.4. At the end of the test, record the final heat exchanger outlet water temperature (T_OHX), fuel consumed, electricity consumed from time t=0, and the time elapsed from the start of the test.

7.3.5. Standby Loss Calculation

7.3.5.1. Once the test is complete, use the following equation to calculate the standby loss as a percentage (per hour) of the heat content of the stored water above room temperature:

Where,

ΔT₁ = Heat exchanger outlet water temperature (T_OHX) measured after the pump purge operation is complete (if the unit is integrated with pump purge functionality); or after the main burner(s) cut-out (if the unit is not equipped with pump purge functionality) minus heat exchanger outlet water temperature (T_OHX) measured at the end of the test, expressed in °F

ΔT₂ = Heat exchanger outlet water temperature (T_OHX) minus the ambient temperature, both measured after the main burner(s) cut-out, at the start of the test, expressed in °F

K = 8.25 Btu/gallon· °F, the nominal specific heat of water

V_a = Volume of water contained in the water heater in gallons measured in accordance with section 4 of this appendix

E_t = Thermal efficiency of the water heater determined in accordance with section 6 of this appendix, expressed in %

E_c = Electrical energy consumed by the water heater during the duration of the test in Btu

t = Total duration of the test in hours

S = Standby loss, the average hourly energy required to maintain the stored water temperature expressed as a percentage of the initial heat content of the stored water above room temperature

7.3.5.2. The standby loss expressed in terms of Btu per hour must be calculated as follows:

1. Placement of Water Heater. A water heater for installation on combustible floors must be placed on a 3⁄4-inch plywood platform supported by three 2 × 4-inch runners. If the water heater is for installation on noncombustible floors, suitable noncombustible material must be placed on the platform. When the use of the platform for a large water heater is not practical, the water heater may be placed on any suitable flooring. A wall-mounted water heater must be mounted on a simulated wall section.

2.

2. Test Configuration. If the instantaneous water heater is not required to be tested using a recirculating loop, then set up the unit in accordance with Figure 2.1, 2.2, or 2.3 of this appendix (as applicable). If the unit is required to be tested using a recirculating loop, then set up the unit as per Figure 2.4 of this appendix.

2.2.1. If the instantaneous water heater does not have any external piping, install an outlet water valve within 10 inches of the piping length of the water heater jacket or enclosure. If the instantaneous water heater includes external piping assembled at the manufacturer's premises prior to shipment, install water valves in the outlet piping within 5 inches of the end of the piping supplied with the unit.

2.2.2. If the water heater is not able to achieve an outlet water temperature of 70 °F ± 2 °F above the supply water temperature at a constant maximum electricity input rate, a recirculating loop with pump as shown in Figure 2.4 of this appendix must be used.

3. Test Conditions

4. Determination of Storage Volume. Determine the storage volume by subtracting the tare weight—measured while the system is dry and empty—from the weight of the system when filled with water and dividing the resulting net weight of water by the density of water at the measured water temperature. The volume of water contained in the water heater must be computed in gallons.

5. Standby Loss Test. Perform the steady-state verification period in accordance with section 5.1 of this appendix. For thermostatically-activated instantaneous water heaters with an internal thermostat, use section 5.2 of this appendix to conduct the standby loss test, and for flow-activated and/or thermostatically-activated instantaneous water heaters with an external thermostat (including remote thermostatically activated and/or flow-activated instantaneous water heaters), use section 5.3 of this appendix to conduct the standby loss test.

Set the primary control in accordance with section 3.5 of this appendix, such that the primary control is always calling for heat and the water heater is operating at its full rated input. Begin drawing water from the unit by opening the main supply and the outlet water valve, and adjust the water flow rate to achieve an outlet water temperature of 70 °F ± 2 °F above supply water temperature. At this time, begin recording the parameters specified in section 3.7.1 of this appendix. The steady-state verification period is complete when there is a continuous 30-minute period where the steady-state conditions specified in section 5.1 of this appendix are met, as confirmed by consecutive readings of the relevant parameters recorded at 1-minute intervals (except for electric power input rate, which is determined at 10-minute intervals, as specified in section 3.7.1 of this appendix).

5.2. Thermostatically-Activated Instantaneous Water Heaters with an Internal Thermostat. For water heaters that will experience cut-in based on a temperature-activated control that is internal to the water heater, use the following steps to conduct the standby loss test.

5.2.1. Immediately after the steady-state verification period, turn off the outlet water valve(s) (installed as per the provisions in section 2.2 of this appendix), and the water pump (if applicable) simultaneously and ensure that there is no flow of water through the water heater.

5. 2.2. After the first cut-out following the steady-state verification period, allow the water heater to remain in standby mode. Do not change any settings on the water heater at any point until measurements for the standby loss test are finished. Begin recording the applicable parameters specified in section 3.7.2 of this appendix.

5. 2.3. At the second cut-out, record the time and ambient room temperature, and begin measuring the electricity consumption. Record the initial heat exchanger outlet water temperature (T_OHX) and initial ambient room temperature. For the remainder of the test, continue recording the applicable parameters specified in section 3.7.2 of this appendix.

5. 2.4. Stop the test after the first cut-out that occurs after 24 hours, or at 48 hours, whichever comes first.

5. 2.5. Immediately after conclusion of the standby loss test, record the total electrical energy consumption, the final ambient room temperature, the duration of the standby loss test, and if the test ends at 48 hours without a cut-out, the final heat exchanger outlet temperature, or if the test ends after a cut-out, the maximum heat exchanger outlet temperature that occurs after the cut-out. Calculate the average of the recorded values of the heat exchanger outlet water temperature and of the ambient air temperatures taken at each measurement interval, including the initial and final values.

5. 2.6. Standby Loss Calculation. Calculate the standby loss, expressed as a percentage (per hour) of the heat content of the stored water above room temperature, using the following equation:

Where,

ΔT₃ = Average value of the heat exchanger outlet water temperature (T_OHX) minus the average value of the ambient room temperature, expressed in °F

ΔT₄ = Final heat exchanger outlet water temperature (T_OHX) measured at the end of the test minus the initial heat exchanger outlet water temperature (T_OHX) measured at the start of the test, expressed in °F

k = 8.25 Btu/gallon· °F, the nominal specific heat of water

V_a = Volume of water contained in the water heater in gallons measured in accordance with section 4 of this appendix

E_t = Thermal efficiency = 98 percent for electric water heaters with immersed heating elements

E_c = Electrical energy consumed by the water heater during the duration of the test in Btu

t = Total duration of the test in hours

S = Standby loss, the average hourly energy required to maintain the stored water temperature expressed as a percentage of the initial heat content of the stored water above room temperature

5.3. Flow-Activated and Thermostatically-Activated Instantaneous Water Heaters with an External Thermostat. For water heaters that are either flow-activated or thermostatically-activated with an external thermostat, use the following steps to conduct the standby loss test:

5.3.1. Immediately after the steady-state verification period, de-energize the primary control to end the call for heating. If the heating elements do not cut out, then turn off the electricity supply to the heating elements. After the heating elements have cut-out, or the electricity supply to the heating elements is turned off, begin recording the measurements as per the requirements in section 3.7.2 of this appendix.

5.3.1.1. If the unit does not have an integral pump purge functionality, then turn off the outlet water valve and water pump immediately after the main burners cut-out.

5.3.1.2. If the unit has an integral pump purge functionality, allow the pump purge operation to continue. After the pump purge operation is complete, immediately turn off the outlet water valve and water pump and continue recording the required parameters for the remainder of the test.

5.3.2. Recording Data

5.3.2.1. For units with pump purge functionality, record the initial heat exchanger outlet water temperature (T_OHX), and ambient room temperature when the main heating element(s) cut-out or the electricity supply to the heating element(s) is turned off. After the pump purge operation is complete, record the time as t = 0 and the initial electricity meter reading. Continue to monitor and record the heat exchanger outlet water temperature (T_OHX) and time elapsed from the start of the test as per the requirements in section 3.7.2 of this appendix.

5.3.2.2. For units not equipped with pump purge functionality, begin recording the measurements as per the requirements of section 3.7.2 of this appendix when the main heating element(s) cut-out or the electricity supply to the heating element(s) is turned off. Specifically, record the time as t = 0, and record the initial heat exchanger outlet water temperature (T_OHX), ambient room temperature, and electricity meter readings. Continue to monitor and record the heat exchanger outlet water temperature (T_OHX) and the time elapsed from the start of the test as per the requirements in section 3.7.2 of this appendix.

5.3.3. Stopping Criteria. Stop the test when one of the following occurs:

5.3.3.1. The heat exchanger outlet water temperature (T_OHX) decreases by 35 °F from its value recorded after the main heating element(s) have cut-out, and the pump purge operation (if applicable) is complete; or

5.3.3.2. 24 hours have elapsed from the start of the test.

5. 3.4. At the end of the test, record the final heat exchanger outlet water temperature (T_OHX), electricity consumed from time t = 0, and the time elapsed from the start of the test.

5.3.5. Standby Loss Calculation. Calculate the standby loss, expressed as a percentage (per hour) of the heat content of the stored water above room temperature, using the following equation:

1. Test set-up and installation instructions.

4.1.1. For air-source CHPWHs, set up the unit for testing as per section 7.1 and Figure 5a of ANSI/ASHRAE 118.1-2012 for CHPWHs without an integral storage tank, and as per Figure 6 in section 7.7.1 of ANSI/ASHRAE 118.1-2012 for CHPWHs with an integral storage tank.

4. 1.2. For direct geo-exchange CHPWHs, set up the unit for testing as per section 7.1 and Figure 5b of ASNI/ASHRAE 118.1-2012 for CHPWHs without an integral storage tank, and as per Figure 7 in section 7.7.2 of ANSI/ASHRAE 118.1-2012 for CHPWHs with an integral storage tank.

4. 1.3. For indoor water-source, ground-source closed-loop, and ground water-source CHPWHs, set up the unit for testing as per section 7.1 and Figure 5c of ANSI/ASHRAE 118.1-2012 for CHPWHs without an integral storage tank, and as per Figure 8 in section 7.7.3 of ANSI/ASHRAE 118.1-2012 for CHPWHs with an integral storage tank.

4. 2. Use the water piping instructions described in section 7.2 of ANSI/ASHRAE 118.1-2012 and the special instructions described in section 7.7.6 of ANSI/ASHRAE 118.1-2012. Insulate all the pipes used for connections with material having a thermal resistance of not less than 4 h· °F·ft²/Btu for a total piping length of not less than 4 feet from the water heater connection ports.

4.3. Install the thermocouples, including the room thermocouples, as per the instructions in sections 7.3.1, 7.3.2, and 7.3.3 (as applicable) of ANSI/ASHRAE 118.1-2012.

4.4. Section 7.6 of ANSI/ASHRAE 118.1-2012 must be used if the manufacturer neither submits nor specifies a water pump applicable for the unit for laboratory testing.

4.5. Install the temperature sensors at the locations specified in Figure 5a, 5b, 5c, 6, 7, or 8 of ANSI/ASHRAE 118.1-2012, as applicable as per section 4.1 of this appendix. The sensor shall be installed in such a manner that the sensing portion of the device is positioned within the water flow and as close as possible to the center line of the pipe. Follow the instructions provided in sections 7.7.7.1 and 7.7.7.2 of ANSI/ASHRAE 118.1-2012 to install the temperature and flow-sensing instruments.

4.6. Use the following evaporator side rating conditions as applicable for each category of CHPWHs. These conditions are also mentioned in Table 5.1 of this appendix:

4.6.1. For air-source CHPWHs, maintain the evaporator air entering dry-bulb temperature at 80.6 °F ± 1 °F and wet-bulb temperature at 71.2 °F ± 1 °F throughout the conduct of the test.

4.6.2. For direct geo-exchange CHPWHs, maintain the evaporator refrigerant temperature at 32 °F ± 1 °F.

4.6.3. For indoor water-source CHPWHs, maintain the evaporator entering water temperature at 68 °F ± 1 °F.

4.6.4. For ground water-source CHPWHs, maintain the evaporator entering water temperature at 50 °F ± 1 °F.

4.6.5. For ground-source closed-loop CHPWHs, maintain the evaporator entering water temperature at 32 °F ± 1 °F.

4.6.5.1. For ground-source closed-loop CHPWHs, the evaporator water must be mixed with 15-percent methanol by-weight to allow the solution to achieve the rating conditions required in section 4.6.5.

4.7. The CHPWH being tested must be installed as per the instructions specified in sections 4.1 to 4.6 (as applicable) of this appendix. For all other installation requirements, use section 7.7.4 of ANSI/ASHRAE 118.1-2012 to resolve any issues related to installation (other than what is specified in this test procedure) of the equipment for testing. Do not make any alterations to the equipment except as specified in this appendix for installation, testing, and the attachment of required test apparatus and instruments.

4. 8. Use Table 3 of ANSI/ASHRAE 118.1-2012 for measurement tolerances of various parameters.

4.9. If the CHPWH is equipped with a thermostat that is used to control the throttling valve of the equipment, then use the provisions in section 7.7.7.3 of ANSI/ASHRAE 118.1-2012 to set up the thermostat.

4.10. For CHPWHs equipped with an integral storage tank, supplemental heat inputs such as electric resistance elements must be disabled as per section 7.7.8 of ANSI/ASHRAE 118.1-2012.

4.11. Install instruments to measure the electricity supply to the equipment as specified in section 7.5 of ANSI/ASHRAE 118.1-2012.

5. Test Procedure

Test all CHPWHs that are not equipped with an integral storage tank as per the provisions described in ANSI/ASHRAE 118.1-2012 for “Type IV” equipment as defined in section 4.4 of ANSI/ASHRAE 118.1-2012. Test all CHPWHs that are equipped with an integral storage tank as per the provisions described in ANSI/ASHRAE 118.1-2012 for “Type V” equipment as defined in section 4.5 of ANSI/ASHRAE 118.1-2012. Tests for all CHPWHs must follow the steps described below.