pressed in units of kilowatt-hours. Natural gas and propane consumption shall be expressed in units of standard cubic feet, i.e., measured cubic feet corrected to standard conditions of 60° F. temperature and 30 inches of mercury column pressure. Fuel oil consumption is to be expressed in units of gallons. Also install one or more instruments which measure, as appropriate, and with an error no greater than 1 percent, the rate of electrical energy, natural gas, propane or fuel oil consumption by a water heater. The rate of electrical energy consumption shall be expressed in units of kilowatts. The rate of natural gas and propane consumption shall be expressed in units of standard cubic feet per hour. The rate of fuel oil consumption shall be expressed in units of gallons per hour.

2.8 Room ambient temperature. Maintain the ambient air temperature of the test room between 65° F. and 85° F. at all times during the test, as measured according to section 3.5. The ambient air temperature during these tests shall not vary more than +7° F. from the average ambient air temperature determined as the arithmetic average of the air temperatures measured periodically at intervals no greater than 15 minutes throughout the duration of the test.

3. TEST PROCEDURES AND MEASUREMENTS

3.1 Tank storage capacity. Determine the storage capacity, V, of the water heater under test, in gallons, according to the method specified in section 2.26 of the American National Standard for Gas Water Heaters, Volume I, designated ANS Z21.10.1-1975.

3.2 Power input determination.

3.2.1 Power input determination for gas and oil water heaters and electric water heaters with other than immersed heating elements. Initiate normal operation of the water heater, and by using the appropriate instrumentation specified in section 2.7 and the appropriate fuel heating values of section 2.4, determine the power input, P, to the main burners (including pilot light power, if any) or heating elements of the water heater under test, in Btu per hour or kilowatts, as appropriate. In addition, determine the power input, pr to any auxiliary electrical system of a gas or oil water heater when the main burners are in operation, in kilowatts; and the power input, ps, to any auxiliary electrical system of a gas or oil water heater when the main burners are not in operation, in kilowatts.

3.2.2 Power input determination for electric water heaters with immersed heating elements. The power input, P, to the heating element of an electric water heater with one immersed heating element shall be taken to be the design power rating of the heating element. For an electric water heater with dual immersed heating elements, the power

input, P, to the heating elements shall be taken to be the arithmetic mean of the design power ratings of the heating elements, if, in characteristic operation of the water heater, only one heating element will be energized at any time; otherwise, P shall be taken to be the sum of the design power ratings of the heating elements.

3.3 Recovery efficiency.

3.3.1 Recovery efficiency for gas and oil water heaters and electric water heaters with other than immersed heating elements. With the water heater turned off, fill the tank with water and eliminate any residual air remaining in the tank. If the mean tank temperature is constant and within 70° F.±2° F., record the mean tank temperature, initiate normal operation of the water heater, and begin measuring the fuel or energy flow to the burners (including pilot light fuel if any) or heating elements of the water heater using the appropriate instrumentation specified in section 2.7 After cutout determine the maximum mean tank temperature and record the total fuel flow, Qr, for a gas or oil water heater, or the total electrical energy flow, Zr, to the heating elements of an electric water heater, from initiation to cutout. Record the temperature difference, AT, obtained by subtracting the initial from the final maximum mean tank temperature.

3.3.2 Recovery efficiency for electric water heaters with immersed heating elements. The recovery efficiency for electric water heaters with immersed heating elements is derived from the results of the standby loss tests of section 3.4.2.

3.4 Standby loss.

3.4.1 Standby loss for gas and oil water heaters and electric water heaters with other than immersed heating elements. Establish normal water heater operation within the maximum mean tank temperature within the range specified in section 2.6 and with all air eliminated from the tank. Begin the standby loss test immediately after cutout. At the beginning of the standby loss test record the time, the mean tank temperature, the ambient air temperature, and begin measuring the fuel or energy flow to the burners (including pilot light fuel if any) or heating elements of the water heater using the appropriate instrumentation specified in section 2.7.

At the end of the first 15 minute interval and at the end of each subsequent 15 minute interval following the beginning of the test, record the mean tank temperature and the ambient air temperature. Continue these measurements until the end of a 48 hour period unless a main heating element or burner is on at that time, in which case, continue these measurements until the first subsequent cutout. When the test is terminated, record the total fuel flow, Q., for a

gas or oil water heater, or the total electrical energy flow, Z,, to the heating elements of an electric water heater, from the beginning to the end of the test period, the final mean tank temperature, the final ambient air temperature, and the time duration, t, of the standby loss test, in hours rounded off to the nearest tenth of an hour, which elapsed from the beginning to the end of the test period. Calculate the average of the recorded values of the mean tank temperatures and of the ambient air temperatures taken at the end of each time interval, inIcluding in each case the initial and final values. Determine the difference, AI, between these two averages by subtracting the latter from the former, and the difference, AI.. between the final and initial mean tank temperatures by subtracting the latter from the former.

3.4.2 Standby loss for electric water heaters with immersed heating elements. All water heaters to be tested must be equipped with immersed heating elements that have a design power rating of 4,500 watts unless such a design power rating exceeds the maximum design power rating specified by the manufacturer for the water heater to be tested, in which case the standby loss test will be conducted with the water heater equipped with immersed heating elements of a design power rating equal to the manufacturer's specified maximum design power rating. All water heaters capable of operating with dual immersed heating elements will be equipped and tested with dual immersed heating elements of equal design power rating in accordance with the provisions specified above. Tests shall be conducted in accordance with the same procedures as those specified in section 3.4.1.

3.5 Room temperature measurement. Room temperature wherever specified shall be the temperature determined by using the test room thermocouple described in section 2.5.

3.6 Mean tank temperature measurement. Mean tank temperature, the average temperature of the water in a water heater tank, whever specified shall be the mean of the temperatures determined by using the six water heater tank thermocouples described in section 2.5.

3.7 First hour rating water draw test. Establish normal water heater operation with the maximum mean tank temperature within the range specified in section 2.6 and with all air eliminated from the tank. Begin the first hour rating water draw test immediately after a cutout by recording the hot water outlet water temperature, recording the time, and withdrawing water from the water heater through the hot water outlet at a rate of 5.0±0.25 gallons per minute. Interrupt electrical power to the heating elements or fuel to the main burner of the water heater to prevent their operation

during this test. Collect a withdrawn from the wate the test in a suitable conta pose of determining its we clusion of the test. Altern flow meter may be used volume of water withdrawn heater directly. Beginning the start of the test and at e 15 second interval through of the water draw, record temperature. For the purp the maximum recorded te be referred to as the init temperature, T.. Monitor th the water heater thermos the time that a thermosta heater acts to operate a he the main burner. Continue of water until the outlet wa drops to a value 20°F below temperature, at which tim withdrawal. Determine the water withdrawn, W, in p with an error no greater th the volume of water withd lons measured with an error 2 percent. Determine the a of the outlet water tempera corded, Tm, in °F. Determ time of the test prior to a th water heater acting to opera ment or the main burner, t ured with an error no grea cent. If a thermostat on th does not act to operate a he the main burner within one start of the test, the test is and t, expressed as one hour

mined in accordance with section 2.4, expressed in appropriate units.

4.1.2 Recovery efficiency for electric water heaters with other than immersed heating elements. For an electric water heater with other than immersed heating elements, calculate the recovery efficiency, Er, expressed as a dimensionless quantity and defined as:

E, (kx VAT1/Z,×3,412 Btu/kWh), where

k, V, and AT, are as defined in section 4.1.1 Z, total electrical energy flow to the heating elements in the recovery test, determined in accordance with section 3.3.1, expressed in kilowatt-hours.

4.1.3 Recovery efficiency for electric water heaters with immersed heating elements. For an electric water heater with immersed heating elements, calculate the recovery efficiency, Er, expressed as a dimensionless quantity and defined as:

Er=1-(Sxk×V×▲ T2/Px3,412 Btu/kWh),

where

k and V are as defined in section 4.1.1 S standby loss, as calculated in section 4.4.2.

AT2 45° F., the nominal average difference between the mean tank temperature and the ambient air temperature during recovery.

P water heater input power, determined in accordance with section 3.2.2, expressed in kilowatts.

4.2 Standby loss.

4.2.1 Standby loss for gas and oil water heaters. For a gas or oil water heater, calculate the standby loss, expressed in hour-' and defined as:

S=(Q,xH/k×V×▲T1×t)–(AT./AT3× t× E)

where

k, V, and H are as defined in section 4.1.1 E, is as calculated in section 4.1.1 Q= total fuel flow in the standby loss test, determined in accordance with section 3.4.1, expressed in appropriate units.

AT difference between the average value of the mean tank temperature and the average value of the ambient air temperature during the standby loss test, determined in accordance with section 3.4.1, expressed in ° F.

AT, difference between the initial and final mean tank temperatures, determined in accordance with section 3.4.1, expressed in ° F.

t=duration of the standby loss test, determined in accordance with section 3.4.1, expressed in hours.

4.2.2 Standby loss for electric water heaters. For an electric water heater, calculate

k and V are as defined in section 4.1.1. Z1 = total electrical energy flow to the heating elements in the standby loss test, determined in accordance with section 3.4.1 for electric water heaters with other than immersed heating elements, or section 3.4.2 for electric water heaters with immersed heating elements, expressed in kilowatt-hours. AT, difference between the average value of the mean tank temperature and the average value of the ambient air temperature during the standby loss test, determined in accordance with section 3.4.1 for electric water heaters with other than immersed heating elements, or section 3.4.2 for electric water heaters with immersed heating elements, expressed in kilowatt-hours. AT, difference between the initial and final mean tank temperatures, determined in accordance with section 3.4.1 for electric water heaters with other than immersed heating elements, or section 3.4.2 for electric water heaters with immersed heating elements, expressed in kilowatt-hours.

t=duration of the standby loss test, deter

mined in accordance with section 3.4.1 for electric water heaters with other than immersed heating elements, or section 3.4.2 for electric water heaters with immersed heating elements, expressed in hours.

Er Er as calculated in section 4.1.2 for electric water heaters with other than immersed heating elements, or 0.98 for electric water heaters with immersed heating elements.

k and V are as defined in section 4.1.1. S is as calculated in section 4.2.1 for gas and oil water heaters, or section 4.2.2 for electric water heaters.

AT. 90° F., the nominal difference between the mean tank temperature and the ambient air temperature.

4.5 Average daily energy consumption. 4.5.1 Average daily auxiliary electric energy consumption for gas and oil water heaters. For a gas or oil water heater, calculate the average daily auxiliary electrical energy consumption, Caur, expressed kilowatt-hours per day and defined as:

where

Caur PrX(Cun/P)+ps [24 (hours/ day)-(C/P)]

Cuch is as calculated in section 4.3. P power input to the burner, determined in accordance with section 3.2.1, expressed in Btu per hour.

pr-power input to any auxiliary electrical system during periods of main burner operation, determined in accordance with section 3.2.1, expressed in kilowatts.

Ps=power input to any auxiliary electrical

system during periods when the main burner is not in operation, determined in accordance with section 3.2.1, expressed in kilowatts.

4.5.2 Average daily gas or oil energy consumption for gas and oil water heaters. For a gas or oil water heater, calculate the average daily gas or oil energy consumption, Cr, as appropriate, expressed in Btu per day and defined as:

where

k is as defined in section 4.1.1. AT, is as defined in section 4.3 E, is as calculated in section 4