[Federal Register Volume 77, Number 108 (Tuesday, June 5, 2012)]
[Proposed Rules]
[Pages 33106-33120]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-13609]
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DEPARTMENT OF ENERGY
10 CFR Part 430
[Docket No. EERE-2010-BT-TP-0023]
RIN 1904-AC26
Energy Conservation Program: Test Procedure for Microwave Ovens
AGENCY: Office of Energy Efficiency and Renewable Energy, Department of
Energy.
ACTION: Notice of data availability; request for comment.
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SUMMARY: The U.S. Department of Energy (DOE) initiated a test procedure
rulemaking to develop active mode testing methodologies for residential
microwave ovens. DOE conducted testing to evaluate potential test
procedure amendments to provide methods of measuring energy use for
microwave ovens, including both microwave-only ovens and convection
microwave cooking ovens. In today's notice, DOE presents the results
from these testing investigations and requests comment and additional
information on these results and potential amendments to the microwave
oven test procedure.
DATES: DOE will accept comments, data, and information regarding this
notice submitted no later than July 5, 2012.
ADDRESSES: Any comments submitted must identify the Notice of Data
Availability for Microwave Ovens, and provide docket number EERE-2010-
BT-TP-0023 and/or RIN 1904-AC26. Comments may be submitted using any of
the following methods:
1. Federal eRulemaking Portal: www.regulations.gov. Follow the
instructions for submitting comments.
2. Email: MWO-2010-TP-0023@ee.doe.gov. Include docket EERE-2010-BT-
TP-0023 and/or RIN 1904-AC26 in the subject line of the message.
3. Mail: Ms. Brenda Edwards, U.S. Department of Energy, Building
Technologies Program, Mailstop EE-2J, 1000 Independence Avenue SW.,
Washington, DC 20585-0121. If possible, please submit all items on a
compact disc (CD), in which case it is not necessary to include printed
copies.
4. Hand Delivery/Courier: Ms. Brenda Edwards, U.S. Department of
Energy, Building Technologies Program, 6th Floor, 950 L'Enfant Plaza
SW., Washington, DC 20024. Telephone: (202) 586-2945. If possible,
please submit all items on a CD, in which case it is not necessary to
include printed copies.
Docket: The docket is available for review at www.regulations.gov,
including Federal Register notices, public meeting attendee lists and
transcripts, comments, and other supporting documents/materials. All
documents in the docket are listed in the www.regulations.gov index.
However, not all documents listed in the index may be publicly
available, such as information that is exempt from public disclosure.
A link to the docket web page can be found at: http://www.regulations.gov/#!docketDetail;dct=FR%252BPR%
252BN%252BO%252BSR;rpp=10; po=0;D=EERE-2010-BT-TP-0023. This Web page
contains a link to the docket for this notice on the
www.regulations.gov site. The www.regulations.gov Web page contains
simple instructions on how to access all documents, including public
comments, in the docket.
For further information on how to submit a comment or review other
public comments and the docket, contact Ms. Brenda Edwards at (202)
586-2945 or email: Brenda.Edwards@ee.doe.gov.
FOR FURTHER INFORMATION CONTACT:
Mr. Wes Anderson, U.S. Department of Energy, Office of Energy
Efficiency and Renewable Energy, Building Technologies Program, EE-2J,
1000 Independence Avenue SW., Washington, DC 20585-0121. Telephone:
202-586-7335. Email: Wes.Anderson@ee.doe.gov.
In the Office of the General Counsel, contact Mr. Ari Altman, U.S.
Department of Energy, 1000 Independence Ave. SW., Room 6B-159,
Washington, DC 20585. Telephone: 202-287-6307; Email:
Ari.Altman@hq.doe.gov.
SUPPLEMENTARY INFORMATION:
Table of Contents
I. Background
II. Discussion
A. Test Units
B. Water Load Microwave-Only Testing
C. Reheat Food Simulation Mixture Testing
D. Convection Microwave Cooking Testing
[[Page 33107]]
E. Convection Microwave Oven Convection-Only Cooking Testing
F. Cooling Down Energy Use
G. Additional Issues on Which DOE Seeks Comment
I. Background
On July 22, 2010, DOE published in the Federal Register a final
rule for the microwave oven test procedure rulemaking (July 2010 TP
Repeal Final Rule), in which it repealed the regulatory provisions for
establishing the cooking efficiency test procedure for microwave ovens
under the Energy Policy and Conservation Act (EPCA). 75 FR 42579. In
the July 2010 TP Repeal Final Rule, DOE determined that the existing
microwave oven test procedure to measure the cooking efficiency, which
was based on the International Electrotechnical Commission (IEC)
Standard 705-1998 and Amendment 2-1993, ``Methods for Measuring the
Performance of Microwave Ovens for Households and Similar Purposes''
(IEC Standard 705), did not produce representative and repeatable test
results. DOE stated that it was unaware of any test procedures that had
been developed that addressed the concerns with the microwave oven
cooking efficiency test procedure. DOE was also unaware of any research
or data on consumer usage indicating what a representative food load
would be, or any data showing the repeatability of test results. 75 FR
42579, 42581. In addition, in comments received in response to a
separate test procedure notice of proposed rulemaking (NOPR) published
in the Federal Register on October 17, 2008, which addressed provisions
for measuring standby mode and off mode energy use for microwave ovens
(73 FR 62134), interested parties commented that pure water has
relatively low specific resistivity, and actual food items that might
be cooked in a microwave oven would have more salts and thus absorb
microwave energy more efficiently than pure water. Interested parties
stated that, as a result, testing with a water load would likely result
in lower efficiency measurements than would be expected from using
actual food products.
On July 22, 2010, DOE also published in the Federal Register a
notice of public meeting to initiate a separate rulemaking process to
consider new provisions for measuring microwave oven energy efficiency
in active (cooking) mode. 75 FR 42611. DOE held the public meeting on
September 16, 2010 to discuss and receive comments on several issues
related to active mode test procedures for microwave ovens to consider
in developing a new test procedure. DOE received no data or comments at
or after the September 16, 2010 public meeting suggesting potential
methodologies for test procedures for microwave oven active mode.
On October 24, 2011, DOE published a Request for Information (RFI)
notice to announce that it has initiated a test procedure rulemaking to
develop active mode testing methodologies for microwave ovens. 76 FR
65631. DOE specifically sought information, data, and comments
regarding representative and repeatable methods for measuring the
energy use of microwave ovens, in particular for the microwave-only and
convection microwave cooking (i.e., microwave plus convection and any
other means of cooking) functions. In particular, DOE sought comment on
the following: (1) The characteristics of food loads representative of
consumer use, (2) the repeatability of energy use measurements using
different food loads, and (3) consumer usage data on the hours of
operation in active mode, standby mode, and off mode for the
development of an integrated energy use metric. In response to the
August 2011 RFI, DOE received comments from the Association of Home
Appliance Manufacturers (AHAM) and Whirlpool Corporation (Whirlpool) on
a number of these test procedure issues. These comments are summarized
below.
Food Load Repeatability and Reproducibility. AHAM and Whirlpool
commented that the repeatability (test-to-test within one laboratory)
and reproducibility (lab-to-lab) must be considered in developing an
active mode test procedure for microwave ovens. AHAM and Whirlpool are
both unaware of any existing test procedures that have successfully
incorporated actual food loads, noting that the European Committee for
Electrotechnical Standardization (CENELEC) has conducted testing with
different food loads, including real and artificial food as well as
salt water, and concluded that food loads cannot meet CENELEC's
requirements of repeatability and reproducibility. (AHAM, No. 11 at p.
2, Whirlpool, No. 10 at pp. 1, 3) According to Whirlpool, the most
commonly microwaved foods are hot cereal, bacon, pre-made baked goods,
and frozen vegetables. However, Whirlpool stated the following about
the lack of reproducibility of various foods:
The nature and behavior of fresh foods varies over the
year and by geographical region;
Prefabricated foods change formulation over time and
without notice. Various items are routinely added to and removed from
the market;
The composition of meats such as chicken, beef, and pork
vary from not only by region, but also within each meat category, for
example in the amount of fat or the size of granulation. (Whirlpool,
No. 10 at p. 3)
AHAM and Whirlpool also commented that the IEC evaluated gels, but
they were abandoned due to poor repeatability and excessive preparation
time. (AHAM, No. 11 at p. 2, Whirlpool, No. 10 at p. 3) Whirlpool added
that IEC Standard 60705 Edition 4.0, 2010-04, ``Household microwave
ovens--Methods for measuring performance,'' (IEC Standard 60705 Fourth
Edition) contains food loads, but that those are used for performance
testing only and are not reproducible as is stated in the test
standard. (Whirlpool, No. 10 at p. 2)
Whirlpool stated that the final temperature of the load must be
correlated to normal usage (i.e., heating food to ``eating
temperature''). AHAM and Whirlpool commented that a well-defined final
temperature of food loads cannot be determined with sufficient accuracy
to attain an acceptable level of repeatability. According to Whirlpool,
infrared measurements will only detect surface temperature and
thermocouples will just measure temperature in a few spots and as a
result, cold/hot spots inside the food may not be found. (AHAM, No. 11
at p. 2, Whirlpool, No. 10 at pp. 2, 3)
Convection Microwave Ovens. Whirlpool noted that convection
microwave ovens represent less than 4 percent of U.S. shipments and
that qualitative data suggests that even when consumers own a
convection microwave oven, the use of the convection microwave cooking
function is very limited. Whirlpool commented that the European
Commission established a mandate to define a test method for the
microwave-only cooking function and that the convection microwave
cooking function has not been on the agenda. However, Whirlpool noted
that CENELEC tested convection microwave ovens but was unsuccessful at
developing repeatable and reproducible test loads and testing
procedures for the reasons discussed above. (Whirlpool, No. 10 at p. 1,
2)
Test Methods for DOE Test Procedure. Whirlpool commented that DOE
should not attempt to develop a test procedure for both microwave-only
and convection microwave ovens at this time because the challenge to
develop just a microwave-only test procedure is significant.
(Whirlpool, No. 10 at p. 1) AHAM commented that the issues associated
with the test procedure are not unique to the United States because
microwave ovens do not vary
[[Page 33108]]
significantly across countries. AHAM noted that microwave ovens do not
represent a large amount of energy consumption as compared to other
products, and that DOE should not direct its limited resources to
duplicate what another group has adequately done. (AHAM, No. 11 at p.
2)
AHAM and Whirlpool commented that if DOE proceeds with a test
procedure, it should develop a test procedure for microwave-only ovens
that is harmonized with IEC Standard 60705, which is currently being
updated based on extensive testing. AHAM and Whirlpool noted that the
draft revised IEC Standard 60705, which uses varying water loads (1000
grams (g), 350 g, and 275 g), was evaluated in a round robin testing
program completed in July 2011 and the results verified that the
testing procedures have acceptable repeatability and reproducibility.
Whirlpool also commented that the three amounts of water defined in the
test procedure give good correlation to ``normal usage'' and the water
temperature rise of 50 degrees Celsius ([deg]C) achieves eating
temperature. (AHAM, No. 11 at p. 2, Whirlpool, No. 10 at pp. 3-4)
Based on DOE's determination to initiate a microwave oven active
mode test procedure rulemaking and comments received on the October
2011 RFI discussed above, DOE conducted testing to evaluate potential
amendments to its microwave oven test procedure to provide methods for
measuring the active mode energy use for these products. The sections
below present DOE's tests results and the analytical approaches that it
is considering for potential amendments to the microwave oven test
procedure to measure active mode energy use.
II. Discussion
A. Test Units
In order to evaluate potential amendments to the microwave oven
test procedure, DOE selected a number of test units representative of
products currently available on the U.S. market. DOE considered
features such as installation configuration, cooking functions (i.e.,
microwave cooking, convection microwave cooking), rated output power,
and rated cavity volume. The test units and key features are presented
below in Table 1. Unless otherwise noted, the test unit numbers
presented in Table 1 correspond to the test units in the tables
presenting test results in today's notice.
Table 1--Microwave Oven Test Units and Features
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Rated microwave Rated cavity
Product type Test unit power output (W) volume (ft\3\)
----------------------------------------------------------------------------------------------------------------
Microwave-Only, Countertop................................ 1 700 0.7
2 1200 2.0
3 1000 1.5
4 1200 1.2
5 1200 1.5
Microwave-Only, Over-the-Range............................ 6 1000 1.7
7 950 1.5
8 1000 2.0
9 1200 2.0
10 1100 2.0
Convection Microwave, Countertop.......................... 11 1000 1.2
12 1100 1.5
13 1000 1.0
14 900 1.5
Convection Microwave, Over-the-Range...................... 15 1050 1.7
16 1100 1.8
17 950 1.7
18 950 1.7
----------------------------------------------------------------------------------------------------------------
B. Water Load Microwave-Only Testing
As discussed in section 0, DOE's previous active mode test
procedure incorporated portions of IEC Standard 705. These test methods
measured the amount of energy required to raise the temperature of 1
kilogram of water by 10 [deg]C under controlled conditions. The ratio
of usable output power over input power described the energy factor
(EF), a measure of the cooking efficiency.\1\ DOE noted that IEC is in
the process of revising its current test standard for microwave ovens,
IEC Standard 60705 Fourth Edition. In addition to the 10 [deg]C
temperature rise water load test from IEC Standard 705, the draft
revised IEC Standard 60705 includes a new test method that continues to
use water as the cooking load. The draft revised test method involves
measuring the energy consumption required to heat water loads of 275 g,
350 g, and 1000 g, in 400 milliliter (ml), 900 ml, and 2000 ml
borosilicate glass test containers, respectively, by 45-50 [deg]C and
50-55 [deg]C. The results from the two different temperature rise tests
are used to linearly interpolate the energy consumption required to
heat each load by 50 [deg]C. The cooking cycle energy consumption for
each water load size is then weighted based on consumer usage to
calculate the weighted per-cycle cooking energy consumption. In
addition to the cooking cycle energy consumption, the low power energy
consumption while the microwave is cooling down after the completion of
the cooking cycle is also measured for a 15-minute period. This energy
consumption is then added to the cooking energy consumption to
calculate an overall weighted per-cycle energy consumption. DOE
recognizes that these draft revised IEC Standard 60705 testing methods
may be subject to changes during the IEC review process, however DOE
decided to consider this latest available draft revised test method for
potential amendments to the DOE test procedure. Table 2 presents the
key differences between IEC Standard 705 and the draft revised IEC
Standard 60705.
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\1\ The previous DOE microwave oven test procedure also provided
for the calculation of several other measures of energy consumption,
including cooking efficiency and annual energy consumption.
[[Page 33109]]
Table 2--Key Differences Between IEC Standard 705 and Draft Revised IEC
Standard 60705
------------------------------------------------------------------------
Draft revised IEC
Test condition IEC standard 705 standard 60705
------------------------------------------------------------------------
Test Load Type.............. Water............... Water.
Test Load Size.............. 1000 g.............. 275 g, 375 g, 1000
g.
Test Container Size......... 2000 ml............. 400 ml, 900 ml, 2000
ml.
Temperature Requirements.... Ambient Temp.,T0 = Ambient Temp.,T0 =
20 2 23 2
[deg]C. [deg]C.
Starting Water Starting Water
Temp., T1 = T0-(10 Temp., T1 = 10
1 0.5
[deg]C). [deg]C.
Final Water Temp., Final Water Temp.,
T2 = T0 1 [deg]C. 60-65 [deg]C
Test Load Preparation....... Prior to the test, Prior to the test,
water load and test water load and test
container are not container are
allowed to allowed to
equilibrate. equilibrate.
Time Limit to Measure Final 60 seconds.......... 20 seconds.
Temperature.
Measurement Equipment Mass 1 Mass 1
Accuracy. g. g.
Watt-hour 1.5 percent. minus> 1.0 percent.
Temperature 0.25 [deg]C 1
over the range of 7- Kelvin (K).
23 [deg]C for all Water temperature
temperature 1.5 K.
measurements. Also
specifies linearity
of better than 1
percent.
Time Time 1
0.25 seconds. seconds.
Number of Repeat Tests...... Test is carried out No additional repeat
three times unless tests specified.
the power output
value resulting
from second
measurement is
within 1.5 percent
of the value
obtained from the
first measurement.
Cooling Down Energy Use No.................. Yes.
Measured?
------------------------------------------------------------------------
For over-the-range microwave ovens, DOE reviewed installation
instructions for products available on the market. All products
equipped with a venting fan offer two installation conditions for the
venting fan: (1) Exhaust air to the outside and (2) recirculating air
back into the room. DOE noted that for the majority of products, the
default installation configuration for the venting fan was for air
recirculation. As a result, DOE conducted testing with the venting fan
installed in the air recirculation configuration and did not conduct
testing using the exhaust configuration with additional requirements
for venting.
DOE selected 15 microwave ovens in its test sample and conducted
testing according to the draft revised IEC Standard 60705 to evaluate
the repeatability of test results and the suitability for incorporating
such methods into the DOE microwave oven test procedure.\2\ For each
test unit, DOE conducted two to three identical repeat tests. Table 3
through Table 5 present the cooking cycle energy consumption test
results for each water load size. DOE noted that for the 275 g and 350
g water load sizes, the test-to-test variation expressed in terms of
standard error ranged from roughly 0.1 percent to 2.5 percent, with
averages of approximately 1.1 percent. For the 1000 g water load size,
the test-to-test variation ranged from approximately 0.1 percent to 0.8
percent, with an average of 0.44 percent.
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\2\ Although the draft revised IEC Standard 60705 specifies that
the accuracy of ambient temperature and water temperature
measurements to be 1 K and 1.5 K,
respectively, testing conducted by DOE used thermocouples for
temperature measurements with an accuracy of 0.2
[deg]C, which meets the requirements of IEC Standard 705.
Table 3--Draft Revised IEC Standard 60705 275 g Water Load Test Results
----------------------------------------------------------------------------------------------------------------
Cooking cycle energy use (Wh) Test-to-test
Product type Test unit -------------------------------------------- variation--standard
Test 1 Test 2 Test 3 Average error (%)
----------------------------------------------------------------------------------------------------------------
Microwave-Only, Countertop.......... 1 34.27 34.28 34.47 34.34 0.34
2 36.13 36.76 36.58 36.49 0.88
3 37.97 36.95 ......... 37.46 1.93
4 33.03 32.05 ......... 32.54 2.12
5 34.52 35.66 ......... 35.09 2.31
Microwave-Only, Over-the-Range...... 6 35.27 34.92 ......... 35.09 0.71
7 35.18 36.00 ......... 35.59 1.63
9 40.14 39.19 ......... 39.67 1.70
10 33.96 34.63 34.54 34.38 1.05
Convection Microwave, Countertop.... 11 46.53 46.69 ......... 46.61 0.25
12 45.50 46.14 45.94 45.86 0.70
13 41.75 41.47 ......... 41.61 0.48
Convection Microwave, Over-the-Range 15 36.07 36.15 ......... 36.11 0.17
16 38.29 37.41 38.86 38.18 1.91
17 40.83 40.80 40.83 40.82 0.05
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Average......................... ......... ......... ......... ......... 37.99 1.08
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[[Page 33110]]
Table 4--Draft Revised IEC Standard 60705 350 g Water Load Test Results
----------------------------------------------------------------------------------------------------------------
Cooking cycle energy use (Wh) Test-to-test
Product type Test unit -------------------------------------------- variation--standard
Test 1 Test 2 Test 3 Average error (%)
----------------------------------------------------------------------------------------------------------------
Microwave-Only, Countertop.......... 1 39.50 39.50 39.43 39.48 0.10
2 42.81 42.87 41.26 42.31 2.16
3 44.46 42.86 ......... 43.66 2.59
4 39.65 39.29 ......... 39.47 0.65
5 39.11 39.17 ......... 39.14 0.11
Microwave-Only, Over-the-Range...... 6 43.35 43.63 ......... 43.49 0.46
7 42.74 43.76 ......... 43.25 1.68
9 43.96 44.35 ......... 44.15 0.62
10 40.25 39.64 40.60 40.16 1.20
Convection Microwave, Countertop.... 11 55.05 54.31 ......... 54.68 0.95
12 53.85 52.36 53.07 53.10 1.41
13 47.43 47.64 ......... 47.54 0.31
Convection Microwave, Over-the-Range 15 42.71 42.91 ......... 42.81 0.32
16 45.21 43.89 45.19 44.77 1.69
17 47.59 46.28 47.63 47.17 1.62
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Average......................... ......... ......... ......... ......... 44.34 1.06
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Table 5--Draft Revised IEC Standard 60705 1000 g Water Load Test Results
----------------------------------------------------------------------------------------------------------------
Cooking cycle energy use (Wh) Test-to-test
Product type Test unit -------------------------------------------- variation--standard
Test 1 Test 2 Test 3 Average error (%)
----------------------------------------------------------------------------------------------------------------
Microwave-Only, Countertop.......... 1 116.06 115.08 115.42 115.52 0.43
2 106.02 105.48 105.38 105.63 0.33
3 107.59 108.72 ......... 108.16 0.74
4 104.93 104.8 ......... 104.86 0.09
5 106.54 106.18 ......... 106.36 0.24
Microwave-Only, Over-the-Range...... 6 115.69 116.74 ......... 116.22 0.64
7 113.91 114.53 ......... 114.22 0.38
9 117.14 117.80 ......... 117.47 0.40
10 107.44 107.85 107.04 107.44 0.38
Convection Microwave, Countertop.... 11 128.77 127.35 ......... 128.06 0.78
12 131.95 130.17 130.5 130.87 0.72
13 114.97 115.11 ......... 115.04 0.09
Convection Microwave, Over-the-Range 15 112.54 111.69 ......... 112.12 0.54
16 120.83 120.18 119.56 120.19 0.53
17 121.71 120.95 121.2 121.29 0.32
---------------------------------------------------------------------------
Average......................... ......... ......... ......... ......... 114.90 0.44
----------------------------------------------------------------------------------------------------------------
Table 6 presents the calculated overall weighted average cooking
cycle energy consumption results for each test unit. The following
weighting factors provided in the draft revised IEC Standard 60705 are
applied to the measured energy use for each test load size to calculate
the weighted energy consumption: 1000 g = 2/11; 350 g = 6/11; 275 g =
3/11. DOE noted that values for the overall weighted average cooking
cycle energy consumption ranged from approximately 50.4 Watt-hours (Wh)
to 66.5 Wh (a 32.2 percent difference). DOE compared the range of
values from testing according to the draft revised IEC Standard 60705
to the testing conducted for the most recent energy conservation
standards rulemaking for microwave ovens. For that testing, DOE
conducted testing on 32 microwave ovens and AHAM conducted tests on 21
separate microwave ovens according to the previous DOE microwave oven
test procedure that was based on IEC Standard 705, with the results
expressed in EF (i.e., the ratio of usable output power over input
power). The DOE test units for the most recent energy conservation
standards rulemaking testing are different from the test units tested
for today's notice listed in Table 1. The results from this testing,
presented in Table 7, showed a much smaller range in the efficiency
metric, with EF values ranging from 54.8 percent to 61.8 percent (12.8
percent difference). Based on these results, DOE believes that the
draft revised IEC Standard 60705 may provide the opportunity to better
differentiate products available on the market based on efficiency and
their associated design options for the purposes of energy conservation
standards rulemakings.
[[Page 33111]]
Table 6--Draft Revised IEC Standard 60705 Overall Weighted Energy Consumption Test Results
----------------------------------------------------------------------------------------------------------------
Overall weighted energy use (Wh) Test-to-test
Product type Test unit -------------------------------------------- variation--standard
Test 1 Test 2 Test 3 Average error (%)
----------------------------------------------------------------------------------------------------------------
Microwave-Only, Countertop.......... 1 51.99 51.82 51.90 51.90 0.17
2 53.27 53.37 51.60 52.75 0.98
3 54.41 53.46 ......... 53.93 1.25
4 50.60 50.11 ......... 50.35 0.68
5 50.51 50.79 ......... 50.65 0.39
Microwave-Only, Over-the-Range...... 6 55.11 55.36 ......... 55.23 0.32
7 54.04 54.93 ......... 54.48 1.16
9 57.31 57.38 ......... 57.34 0.09
10 51.50 51.44 51.79 51.57 0.36
Convection Microwave, Countertop.... 11 66.85 66.24 ......... 66.54 0.65
12 66.72 65.75 66.14 66.20 0.74
13 58.47 58.54 ......... 58.51 0.08
Convection Microwave, Over-the-Range 15 54.58 54.55 ......... 54.57 0.03
16 58.15 57.07 58.06 57.76 1.04
17 59.89 59.03 59.82 59.58 0.80
�������������������������������������
Average......................... ......... ......... ......... ......... 56.11 0.58
----------------------------------------------------------------------------------------------------------------
Table 7--DOE and AHAM IEC Standard 705 Testing Results
------------------------------------------------------------------------
DOE Testing AHAM Testing
------------------------------------------------------------------------
Test
Test unit \1\ EF (%) unit \1\ EF (%)
------------------------------------------------------------------------
1......................................... 57.5 33 57.6
2......................................... 58.0 34 61.1
3......................................... 55.9 35 58.9
4......................................... 59.6 36 57.4
5......................................... 59.5 37 60.7
6......................................... 58.4 38 61.8
7......................................... 57.6 39 55.2
8......................................... 57.3 40 59.1
9......................................... 60.2 41 57.2
10........................................ 56.9 42 57.8
11........................................ 59.4 43 58.7
12........................................ 59.2 44 61.4
13........................................ 59.0 45 56.4
14........................................ 60.8 46 61.4
15........................................ 58.9 47 57.3
16........................................ 60.6 48 55.7
17........................................ 57.2 49 54.8
18........................................ 59.2 50 55.8
19........................................ 58.2 51 59.1
20........................................ 60.4 52 56.8
21........................................ 61.2 53 58.1
22........................................ 56.9 ........ ........
23........................................ 59.4 ........ ........
24........................................ 58.7 ........ ........
25........................................ 61.3 ........ ........
26........................................ 58.0 ........ ........
27........................................ 61.5 ........ ........
28........................................ 60.4 ........ ........
29........................................ 59.7 ........ ........
30........................................ 57.6 ........ ........
31........................................ 58.5 ........ ........
32........................................ 58.0 ........ ........
------------------------------------------------------------------------
Minimum Efficiency = 54.8%
Maximum Efficiency = 61.8%
------------------------------------------------------------------------
\1\ Test units listed in this table are different models than the models
from DOE's latest testing.
DOE also noted that CENELEC conducted a round-robin testing program
to evaluate the repeatability and reproducibility of the draft revised
IEC Standard 60705. A total of 5 manufacturer test labs and 5
independent test labs in Europe conducted testing according to the
draft revised IEC Standard 60705 on 4 microwave oven models. In terms
of repeatability of the measured weighted cooking cycle energy
consumption, the results showed that the test-to-test variation
expressed as standard error within each laboratory was on average 0.56
percent. The lab-to-lab reproducibility of the measured weighted
cooking cycle energy consumption showed a variation of 2.30 percent on
average. CENELEC determined these to be acceptable levels of
repeatability and reproducibility.
DOE also conducted testing to evaluate the testing methodology for
measuring the low power energy consumption of the cooling down period.
The draft revised IEC Standard 60705 requires that the cooking cycle
test be run to achieve a 50 [deg]C temperature rise. When the cooking
cycle has finished, the load is removed from the microwave oven and the
door is closed, at which point the cooling down energy consumption is
measured for a period of 15 minutes. This test is conducted for each of
the three test load sizes, and the weighted cooling down energy
consumption is calculated using the same weighting factors used for the
cooking cycle weighted energy consumption. The weighted cooling down
energy consumption is then added to the weighted cooking cycle energy
consumption to calculate the overall weighted energy consumption. For
the 1000 g load size, DOE conducted two identical repeat tests. For the
275 g and 350 g load sizes, DOE conducted one test each. The results of
this testing are presented below in Table 8.
Table 8--Draft Revised IEC Standard 60705 Cooling Down Energy Consumption Test Results
----------------------------------------------------------------------------------------------------------------
Cooling down energy use (Wh)
-------------------------------------------
Product type Test unit 1000 g 1000 g 350 g 275 g
Test 1 Test 2 Test Test
----------------------------------------------------------------------------------------------------------------
Microwave-Only, Countertop............................... 1 0.00 0.00 0.00 0.00
2 0.81 0.80 0.79 0.78
3 0.23 ......... 0.23 0.25
4 0.88 0.89 0.88 0.88
5 0.39 0.39 0.40 0.39
[[Page 33112]]
Microwave-Only, Over-the-Range........................... 6 0.80 ......... 0.81 0.81
7 0.41 0.41 0.43 0.41
9 1.09 1.10 1.08 1.09
10 0.72 0.78 0.77 0.72
Convection Microwave, Countertop......................... 11 0.72 0.72 0.73 0.73
12 0.92 0.89 0.89 1.07
13 0.31 0.32 0.32 0.31
Convection Microwave, Over-the-Range..................... 15 0.99 0.99 0.97 1.00
16 1.08 1.07 1.07 1.07
17 0.69 0.67 0.67 0.66
----------------------------------------------------------------------------------------------------------------
DOE observed minimal variation in the measured cooling down energy
consumption from test to test and also between the different load
sizes. DOE noted that for all of the units in its test sample, none
contained a fan that operated at the end of the microwave-only cooking
cycle to cool the appliance down. DOE also noted that when the door was
closed after the load was removed at the end of the cooking cycle, the
microwave ovens reverted back to the standby mode. Table 9 presents the
average measured power for the cooling down mode as compared to the
average measured standby mode power for each test unit.
Table 9--Draft Revised IEC Standard 60705 Cooling Down Mode Power
----------------------------------------------------------------------------------------------------------------
Average cooling down power (W)
--------------------------------- Average
Product type Test unit 1000 g 350 g 275 g standby power
Tests Test Test (W)
----------------------------------------------------------------------------------------------------------------
Microwave-Only, Countertop.......................... 1 0.00 0.00 0.00 \1\ 0.00
2 3.24 3.15 3.10 3.18
3 0.90 0.92 1.00 1.06
4 3.55 3.54 3.54 3.52
5 1.56 1.59 1.55 1.63
Microwave-Only, Over-the-Range...................... 6 3.23 3.25 3.25 3.24
7 1.64 1.72 1.64 1.71
9 4.41 4.40 4.38 4.29
10 3.00 3.11 2.90 3.16
Convection Microwave, Countertop.................... 11 2.88 2.91 2.91 2.93
12 3.66 3.58 4.29 3.54
13 1.26 1.26 1.27 1.19
Convection Microwave, Over-the-Range................ 15 3.98 3.90 3.99 3.98
16 4.29 4.30 4.29 4.32
17 2.72 2.69 2.66 2.73
----------------------------------------------------------------------------------------------------------------
\1\ Test unit 1 had electromechanical controls and operated in off mode, consuming 0 W. This unit was not
capable of operating in standby mode.
The repeatability and reproducibility of the cooling down energy
consumption measurement method from the draft revised IEC Standard
60705 was also evaluated as part of the CENELEC round-robin testing
program. In terms of repeatability of the measured weighted cooling
down energy consumption, the results showed that the test-to-test
variation expressed as standard error within each laboratory was on
average 0.24 percent. The lab-to-lab reproducibility of the measured
weighted cooling down energy consumption showed a variation of 6.14
percent on average. CENELEC determined these to be acceptable levels of
repeatability and reproducibility.
DOE may consider incorporating the draft revised IEC Standard 60705
test method into the DOE microwave oven test procedure for measuring
the energy consumption of the microwave-only cooking function. As a
result DOE is seeking comment on the following issues:
1. DOE seeks comment on the suitability of the testing
methodologies provided in the draft revised IEC Standard 60705 for
incorporation into the DOE microwave oven test procedure. In
particular, DOE requests comment on the repeatability and
reproducibility of the test results from both DOE and CENELEC testing.
DOE also welcomes comment on whether the test procedure should require
multiple test runs with the results averaged.
2. DOE requests comment on the accuracy requirements for measuring
equipment specified in the draft revised IEC Standard 60705. In
particular, DOE requests comment on the less stringent requirements for
the accuracy of the temperature measurements as compared to IEC
Standard 705.
3. DOE welcomes comment on the testing burden associated with
testing according to the draft revised IEC Standard 60705. When
providing comments, please quantify and describe the associated testing
burdens.
4. DOE requests consumer usage data on the number of annual active
mode cooking cycles and annual hours spent in active mode for
microwave-only ovens.
5. DOE welcomes comment on the determination to conduct testing for
over-the-range microwave ovens with
[[Page 33113]]
the airflow exhaust/recirculation fan installed in the default air
recirculation configuration. DOE welcomes comment on whether there are
any other installation conditions for over-the-range or built-in
microwave ovens that it should consider for the DOE microwave oven test
procedure.
C. Reheat Food Simulation Mixture Testing
DOE notes that water may not be representative of actual food loads
cooked by consumers in microwave ovens. As a result, DOE conducted
testing on 7 microwave ovens using the microwave-only cooking function
to evaluate mixtures that would simulate food load that may be reheated
in a microwave. The mixtures were composed of water and basic food
ingredients (i.e., fats, sugars, salt, fiber, proteins, etc.) with a
total combined mass of 350 g. DOE selected the 350 g load size (using
the 900 ml borosilicate glass container) based on the draft revised IEC
Standard 60705 weighting factors for the load size with the highest
frequency of use. DOE also conducted testing on an actual food load,
chicken noodle soup, to serve as a comparison to the food simulations.
The mixtures and food load were tested using the same basic testing
methodology as the draft revised IEC Standard 60705 (i.e., microwave-
only cooking function, temperature rise from 10 [deg]C to 60 [deg]C).
The measured cooking cycle energy consumption was then used to
calculate the energy consumption required to heat one gram of the
mixture by one degree Celsius, an effective heat capacity. For each
test unit, three identical tests were conducted for each mixture to
evaluate the repeatability of such a testing procedure.
The results from this testing, presented in Table 10 and Table 11,
show a higher range and average test-to-test variation, expressed as a
standard error, compared to the water-only load and compared to the
results using the draft revised IEC Standard 60705 test method
presented in 0.0. DOE also noted that the same brands were used for
each ingredient in the mixtures. Therefore, additional variation in
test results may be observed from lab to lab due to the use of
different brands of the ingredients.
Table 10--Food Simulation Mixture Test Results--Part 1
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Water Water + fat Water + glucose Water + fat + glucose
---------------------------------------------------------------------------------------------------------------------------
Test-to- Test-to- Test-to- Test-to-
Test unit Average heat test Average heat test Average heat test Average heat test
capacity (J/ variation capacity (J/ variation capacity (J/ variation capacity (J/ variation
g[middot][deg]C) (%) g[middot][deg]C) (%) g[middot][deg]C) (%) g[middot][deg]C) (%)
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1........................................................ 8.570 0.39 8.284 3.57 7.514 1.50 7.672 1.54
2........................................................ 8.635 0.99 8.759 7.20 7.259 1.85 7.416 5.95
8........................................................ * * 8.952 1.67 8.332 1.06 8.241 4.04
9........................................................ 8.363 0.64 8.561 2.39 7.559 2.61 7.293 2.16
11....................................................... 11.419 1.42 10.941 0.87 10.203 1.65 9.704 3.00
15....................................................... 9.356 0.68 8.922 0.11 8.152 0.49 8.028 2.55
16....................................................... 9.833 0.27 9.774 0.41 8.769 1.55 8.790 2.35
--------------------------------------------------------------------------------------------------------------------------------------
Average.............................................. 9.363 0.73 9.170 2.32 8.255 1.53 8.163 3.08
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
* Not tested.
Table 11--Food Simulation Mixture Test Results--Part 2
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pizza simulation Chicken noodle soup Chicken noodle soup
------------------------------- simulation ------------------------------
-------------------------------
Test unit Average heat Test-to- Test-to- Average heat Test-to-
capacity (J/ test Average heat test capacity (J/ test
g[middot][deg]C) variation capacity (J/ variation g[middot][deg]C) variation
(%) g[middot][deg]C) (%) (%)
--------------------------------------------------------------------------------------------------------------------------------------------------------
1.......................................................... 6.975 2.42 8.618 1.09 8.941 2.01
2.......................................................... 6.486 1.24 8.811 3.77 9.210 1.26
8.......................................................... 7.715 1.93 8.952 0.69 9.754 2.67
9.......................................................... 6.453 0.61 8.406 0.73 8.995 3.29
11......................................................... 9.036 0.90 11.108 0.81 11.662 1.39
15......................................................... 7.164 1.28 8.909 0.56 9.236 1.04
16......................................................... 7.715 1.15 9.624 0.88 10.012 1.43
--------------------------------------------------------------------------------------------
Average................................................ 7.363 1.36 9.204 1.22 9.687 1.87
--------------------------------------------------------------------------------------------------------------------------------------------------------
6. DOE welcomes comment on suitability of using food simulation
mixtures for the microwave oven test procedure for microwave-only
cooking. In particular, DOE requests comment on the repeatability and
reproducibility of the food simulation mixture tests results presented
in Table 10 and Table 11.
D. Convection Microwave Cooking Testing
As discussed above in section 0, according to Whirlpool, convection
microwave ovens (i.e., microwave ovens that incorporate convection
features and any other means of cooking in a single compartment)
represent less than 4 percent of U.S. shipments. Based on shipments
data from Appliance Magazine showing 11.340 million microwave oven
shipments in 2008,\3\ convection microwave ovens represent
approximately 450,000 annual shipments.
---------------------------------------------------------------------------
\3\ ``U.S. Appliance Industry: Market Share, Life Expectancy &
Replacement Market, and Saturation Levels.'' Appliance Market
Research Report, Appliance Magazine, January 2010.
---------------------------------------------------------------------------
[[Page 33114]]
DOE's review of product literature indicated that convection
microwave ovens can be operated using the microwave-only cooking
function, convection-only cooking function, and convection microwave
cooking function. DOE also noted based on a review of the cooking
manuals and recipe books supplied with convection microwave ovens that
a significant portion of the recipes included cooking procedures that
used the convection microwave cooking function. As a result, DOE first
investigated whether testing procedures could be developed to evaluate
the convection microwave cooking function of convection microwave
ovens. As discussed in section 0, AHAM and Whirlpool both noted a
number of concerns with the repeatability and reproducibility of test
results using actual food loads. DOE therefore decided to conduct
limited testing to evaluate the repeatability of real food loads when
heated using the convection microwave cooking function. DOE tested
three different food loads: shortening, potatoes, and chicken. For each
food load, the same brand of products was used for all tests to
specifically evaluate repeatability of test results. DOE then conducted
testing to assess food simulation cooking loads to determine whether
such loads are representative of actual food loads and improve the
repeatability of test results.
As part of this testing DOE noted that for the majority of
microwave ovens in its test sample, the default program setting for
convection microwave cooking allowed the user to set the overall
cooking time and cycled between microwave-only cooking and convection-
only cooking, where microwave-only cooking accounted for 30 percent of
the cooking time and convection-only cooking accounted for the
remaining 70 percent of total cooking time. DOE used this default
convection microwave cooking program setting that used 30 percent
microwave-only cooking and 70 percent convection-only cooking for
testing. DOE also noted that for the majority of the convection
microwave ovens in its test sample, the user is required to program the
temperature setting for the convection portion of the convection
microwave cooking cycle. Based on a review of the cooking manuals and
recipe books supplied with convection microwave ovens, DOE noted that a
majority of the recipes that used convection microwave cooking
specified convection temperature settings between 300 degrees
Fahrenheit ([deg]F) and 375 [deg]F. DOE also noted that its current
test procedure for conventional ovens found in 10 Code of Federal
Regulations (CFR) part 430, subpart B, appendix I specifies a
convection temperature setting 325 5 [deg]F higher than
the room ambient air temperature, which would result in a temperature
setting close to 400 [deg]F. However, based on DOE's survey of
convection microwave ovens available on the market, not all products
are equipped with a 400 [deg]F temperature setting, but all convection
microwave ovens DOE surveyed had a 375 [deg]F setting. As a result, DOE
selected a convection temperature setting of 375 [deg]F for the
convection microwave cooking function for its testing of convection
microwave ovens.
For convection microwave cooking testing, DOE noted that the
temperatures of the test loads had to be measured before and after the
cooking cycle, as is done for IEC Standard 60705, due to safety
concerns with arcing inside the microwave oven cavity from the metal
thermocouples and the microwave energy. The following sections discuss
these testing investigations to evaluate the convection microwave
cooking function.
Food Load Testing
For shortening, DOE conducted limited testing on two convection
microwave oven models. For each test, DOE prepared a 350 g load of
shortening in the 900 ml borosilicate glass container with a starting
load temperature of 10 1 [deg]C. DOE used three
thermocouples to measure the average temperature of the load, with one
thermocouple placed in the center of the load, and the other two placed
approximately one inch from the edge of the container on either side.
All of the thermocouples were placed at an equal distance from the top
and bottom of the load. The shortening load was then heated using the
default convection microwave cooking function to achieve a target
average final temperature of 60 5 [deg]C. As for the
reheat food simulation mixture testing, the measured cooking cycle
energy consumption was then used to calculate the effective heat
capacity. For each test unit, DOE conducted three identical tests to
evaluate repeatability. DOE also conducted an additional set of testing
with target average final temperatures of 70 5 [deg]C for
one test unit and 80 5 [deg]C for the other test unit. DOE
was unable to establish a target final average temperature range
tighter than 5 [deg]C due to the test-to-test variation in
the final average temperature of the test load even when using the same
cooking time. DOE noted that using tighter ranges such as
2 [deg]C or 1 [deg]C for this food load would require a
significant number of retests to achieve the specified final average
temperatures.
The test results for the shortening tests are presented below in
Table 12. For the tests using an average final temperature of 60 5 [deg]C, the test-to-test variation ranged from 5.18 percent to
7.42 percent. DOE observed that the shortening, which was all solid at
the starting temperature of 10 1 [deg]C, was only partly
liquefied at the final temperature of approximately 60 [deg]C, with the
middle still being partly solid, and the outer portion being liquid.
Unlike the tests using an average final temperature of 60 [deg]C, DOE
observed that the shortening was all liquid at the end of the cooking
cycle for the 70 [deg]C and 80 [deg]C average final temperature tests.
However, the test results for these tests continued to show significant
test-to-test variation.
For all shortening tests, DOE noted that when it measured the final
temperature of the load after the completion of the cooking cycle, the
temperature continued to rise for 30-90 seconds before finally leveling
off. DOE believes that this may be attributable to continued heat
transfer from the hotter outer edges of the test container and/or food
load after the completion of the cycle. DOE waited until the
temperature leveled off and used that measurement for the calculation
of the effective heat capacity. DOE recognizes that this may contribute
to additional test-to-test variation depending on the time needed for
the temperature of the load to stabilize for each test. DOE also noted
that it had to conduct a number of additional retests in cases where
the final temperature was not within the specified range. DOE
recognizes that specifying a tighter final temperature range than
5 [deg]C may represent a testing burden due to the
difficulties of achieving a consistent final load temperature from test
to test.
[[Page 33115]]
Table 12--Food Load Test Results: Shortening
--------------------------------------------------------------------------------------------------------------------------------------------------------
Target Test 1 Test 2 Test 3
final avg. --------------------------------------------------------------------------------------- Test-to-
Product type Test unit temp range Avg. heat Avg. final Avg. heat Avg. final Avg. heat Avg. final test
of load capacity (J/g temp capacity (J/g temp capacity (J/g temp variation
([deg]C) [middot][deg]C) ([deg]C) [middot][deg]C) ([deg]C) [middot][deg]C) ([deg]C) (%)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Combination, Countertop...... 14 60 5 33.115 83.7 35.924 79.1 31.932 75.9 6.09
80 5
Combination, Over-the-Range.. 17 60 5 25.688 69.1 25.081 68.0 26.199 67.5 2.18
70 5
--------------------------------------------------------------------------------------------------------------------------------------------------------
DOE next conducted testing to evaluate the repeatability of Russet
Burbank potatoes as a test food load using the convection microwave
cooking function. DOE selected potatoes as a test load based on a
review of commonly found foods contained in the cooking manuals and
recipe books supplied with convection microwave ovens. Based on
discussions with a food scientist specializing in potato production and
storage management as well as potato seed quality and performance, DOE
specifically selected Russet Burbank potatoes based on their consistent
water content. In addition, Russet potatoes were identified to be the
most likely to be available year round and are grown with standardized
approaches. For each test DOE selected 3 potatoes with similar weights,
with no greater than an 80 g difference between the largest and
smallest potato for a batch of 3 potatoes. The potatoes were then
placed in an equidistant triangle pattern directly on the turntable
dish at approximately 7 centimeters from the center of the dish. DOE
noted that it was unable to keep a tight tolerance on the total
combined mass due to the variability in size and shape of the potatoes.
The temperature of each potato was measured using single thermocouples
placed approximately at the center of each potato. The potato loads
were heated from 10 1 [deg]C to about 60 5
[deg]C using the convection microwave cooking function. DOE selected
the target final temperature of 60 [deg]C based on a review of the
cooking instructions for potatoes found in the cooking manuals and
recipe books. As was done for the shortening tests, the measured
cooking cycle energy consumption was then used to calculate the
effective heat capacity. For each test unit, DOE conducted three
identical tests to evaluate repeatability. DOE noted that Russet
Burbank potatoes are grown in multiple geographical regions in North
America, the majority of which are grown in Idaho and Canada. DOE
decided to conduct testing to determine whether Russet Burbank potatoes
grown in certain regions produce more repeatable test results. As a
result, DOE tested batches of potatoes from the two areas where the
majority of Russet Burbank potatoes are grown, Idaho and Canada.
The Russet Burbank potato testing results are presented below in
Table 13 and Table 14. The results showed test-to-test variation for
the calculated effective heat capacity ranging from 2.89 percent to
8.50 percent for both types of Russet Burbank potatoes. DOE noted that,
in addition to the varying masses of each of the three test potatoes,
the varying shape of each potato may also affect the time required to
heat the center of each potato to the target final temperature. DOE
also noted that it was difficult to achieve a consistent final average
temperature from test to test due to the different masses and shapes of
the potatoes. DOE observed, similar to the tests for shortening, that
when it measured the final temperature of the load after the completion
of the cooking cycle, the temperature continued to rise for 80-160
seconds in some cases before finally leveling off. DOE waited until the
temperature leveled off and used that measurement for the calculation
of the effective heat capacity. DOE recognizes that this may contribute
to additional test-to-test variation depending on the time needed for
the temperature of the load to stabilize for each test. As with the
shortening tests, DOE noted that it had to conduct a number of
additional retests in cases in which the final temperature was not
within the specified range. DOE similarly recognizes that specifying a
tighter final temperature range than 5 [deg]C for potatoes
may represent a testing burden due to the difficulties of achieving a
consistent final load temperature from test to test.
DOE recognizes that in addition to issues with test-to-test
repeatability, the lab-to-lab reproducibility will also be difficult to
maintain if the potatoes are grown under different conditions,
including climate and growing conditions (i.e., soil conditions,
watering frequency, harvesting time, etc.) that may vary throughout the
growing seasons even within specific geographical regions.
Table 13--Food Load Test Results: Idaho Russet Potato
----------------------------------------------------------------------------------------------------------------
Average heat capacity (J/g [middot][deg]C) Test-to-test
Product type Test unit -------------------------------------------- variation--standard
Test 1 Test 2 Test 3 Average error (%)
----------------------------------------------------------------------------------------------------------------
Convection Microwave, Countertop.... 12 29.541 32.359 31.366 31.089 4.60
14 33.972 39.277 39.732 37.660 8.50
---------------------------------------------------------------------------
Average......................... ......... ......... ......... ......... 34.375 6.55
----------------------------------------------------------------------------------------------------------------
[[Page 33116]]
Table 14--Food Load Test Results: Canadian Russet Potato
----------------------------------------------------------------------------------------------------------------
Average heat capacity (J/g [middot][deg]C) Test-to-test
Product type Test unit -------------------------------------------- variation--standard
Test 1 Test 2 Test 3 Average error (%)
----------------------------------------------------------------------------------------------------------------
Convection Microwave, Countertop.... 13 20.230 22.081 19.741 20.684 5.97
Convection Microwave, Over-the-Range 17 29.145 29.722 30.845 29.904 2.89
18 29.155 27.766 27.300 28.074 3.44
---------------------------------------------------------------------------
Average......................... ......... ......... ......... ......... 26.220 4.10
----------------------------------------------------------------------------------------------------------------
DOE also conducted testing with USDA grade A boneless chicken
breasts using the same basic procedure described for the testing with
potatoes, but with the different starting and final test load
temperatures. DOE noted that chicken is generally stored frozen, and
then allowed to thaw before cooking. To determine an appropriate
starting temperature, DOE used the programmed defrost cycle settings
for chicken on a microwave oven in its test sample and measured the
temperature of the chicken breasts after the defrost cycle. The
temperature of the thawed chicken after the defrost cycle ranged
between 2 to 5 [deg]C. However, at 2 [deg]C, DOE noted that the chicken
breast still had some localized frozen sections not found at 5 [deg]C.
Therefore, DOE used a starting temperature of 5 1 [deg]C.
A target final temperature of 90 5 [deg]C was used based
on review of cooking instructions for chicken found in cooking manuals
and recipe books supplied with convection microwave ovens. For this
testing, DOE selected 3 chicken breasts for each test with similar
weights with no greater than a 170 g difference between the largest and
smallest chicken breast. For each test unit, DOE conducted up to four
identical tests to evaluate repeatability.
The results from testing, presented below in Table 15, showed test-
to-test variation for the calculated effective heat capacity ranging
from 1.09 percent to 12.57 percent, with an average of 7.20 percent.
DOE noted that this variability may be due to the varying masses and
shapes of each chicken breast. DOE also observed, similar to the tests
for shortening and potatoes, that when it measured the final
temperature of the load after the completion of the cooking cycle, the
temperature continued to rise for 60-150 seconds in some cases before
finally leveling off. DOE waited until the temperature leveled off and
used that measurement for the calculation of the effective heat
capacity. DOE recognizes that this may contribute to additional test-
to-test variation depending on the time needed for the temperature of
the load to stabilize for each test. As with the other food load tests,
DOE noted that it had to conduct a number of additional retests in
cases in which the final temperature was not within the specified
range. DOE similarly recognizes that specifying a tighter final
temperature range than 5 [deg]C for chicken may represent
a testing burden due to the difficulties of achieving a consistent
final load temperature from test to test.
DOE recognizes that the following factors may contribute to
variation from chicken to chicken, and thus test to test, as well as
contribute to variation in reproducibility for chicken breasts from
different suppliers:
Individual chicken's diet;
Individual chicken's physical activity;
Genetics; and
Methods of breeding and raising chickens from farm to farm
Table 15--Food Load Test Results: USDA Grade A Boneless Chicken Breast
--------------------------------------------------------------------------------------------------------------------------------------------------------
Range of Average heat capacity (J/g [middot][deg]C)
total ------------------------------------------------------- Test-to-test
Product type Test unit masses variation--standard
(g) Test 1 Test 2 Test 3 Test 4 Average error (%)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Convection Microwave, Countertop...................... 12 700-781 37.449 37.533 36.867 (\1\) 37.283 0.97
14 687-804 34.674 32.619 35.469 34.254 4.29
Convection Microwave, Over-the-Range.................. 17 708-794 32.751 44.727 39.019 39.373 38.967 12.57
-------------------------------------------------------------------------------------------------
Average........................................... ......... ......... ......... ......... ......... ......... 36.835 5.95
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ For test units 12 and 14, DOE conducted only 3 repeat tests.
7. DOE requests comment on the suitability of real food loads for
incorporation into the DOE microwave oven test procedure for testing
convection microwave ovens. DOE also welcomes comments specifically on
the test methodologies (i.e., load temperature measurement methods,
starting and final temperatures, mass of test load) described in this
section and the repeatability of test results using shortening, Russet
Burbank potatoes, and USDA grade A boneless chicken breasts as well as
the reproducibility of such food loads.
Food Load Simulation Testing
As part of the convection microwave cooking testing, DOE also
evaluated loads that would simulate actual foods. As discussed in the
October 2011 RFI, DOE noted that one consumer product review
organization in the UK uses the solidifying powder TX-151, which when
combined with water creates a gel, to simulate a food load (in their
case lasagna).\4\ DOE decided to conduct testing using the TX-151
solidifying powder to evaluate the repeatability of test results using
the convection microwave cooking function. DOE prepared three different
water-solidifying powder mixtures using ratios recommended by the
manufacturer of TX-151 to create medium, medium-hard, and hard firmness
gels, using ratios of powder to water of 1:10, 1:7,
[[Page 33117]]
and 1:5, respectively. DOE noted that when mixing each powder-to-water
ratio, the temperature of the water and mixing speed/time directly
influenced the mixture's homogeneity. As a result, DOE determined,
based on experimentation, the water temperatures and mixing speeds/
times for each powder-to-water ratio that produced the most homogenous
mixtures. DOE also covered the mixtures and allowed them to set for two
different lengths of time (2 hours and 6 hours) and at two different
temperatures (20-25 [deg]C and 7-10 [deg]C) to evaluate whether setting
time and temperature affected the consistency of the gel. DOE observed
that the allowing the gels to set for 6 hours did not noticeably change
the hardness or consistency as compared to the gels that were allowed
to set for 2 hours. In addition, DOE observed in most cases a 0.1 g to
0.3 g loss in water prior to the cooking cycle for both the 2 hour and
6 hour setting times due to evaporation, and that the water loss was
not noticeably higher for the 6 hour setting time. DOE noted that this
was likely because the mixtures were covered while being allowed to
set. Based on these observations, DOE selected the 2 hour setting time
for testing. In addition, DOE noted that the two different setting
temperatures did not result in a noticeably different hardness or
consistency after a given setting time. As a result, DOE selected the
7-10 [deg]C setting temperature so that the temperature of the test
load at the start of the test cycle would be more representative of
food load temperatures at the start of cooking.
---------------------------------------------------------------------------
\4\ For more information, visit http://www.which.co.uk/home-and-garden/kitchen/guides/how-we-test-microwaves/.
---------------------------------------------------------------------------
DOE tested each convection microwave oven in its test sample using
each of the three power-to-water ratio gels (i.e., 1:10, 1:7, and 1:5)
prepared as described above. For each test, DOE prepared 350 g of the
gel mixtures in the 900 ml borosilicate glass containers. Similar to
the method discussed above for shortening, DOE used three thermocouples
to measure the temperature of the load, with one thermocouple placed in
the center of the load, and the other two placed approximately one inch
from the edge of the container on either side, and each thermocouple
placed at an equal distance from the top and bottom of the load. The
test loads were heated from 10 1 [deg]C until the center
temperature was 60 5 [deg]C using the convection microwave
cooking function. DOE chose to use a target final temperature for the
center thermocouple probe because it noted that the temperatures of two
outer thermocouple probes were much more variable and difficult to
repeat. In addition, the temperature at the center of the food load is
generally used to determine whether food is cooked completely. DOE
noted that the target final temperature of 60 5 [deg]C
resulted in an overall average final temperature of approximately 70
5 [deg]C for all three thermocouple probes in most cases.
The results from this testing are presented below in Table 16
through Table 18. For the 1:10 powder-to-water ratio gel, the test-to-
test variation ranged from 1.89 percent to 5.89 percent, with an
average of 4.02 percent. For the 1:7 and 1:5 powder-to-water ratio gel
tests the range in test-to-test variation was greater than the 1:10
powder-to-water ratio gel tests. DOE noted that this may be due to the
1:10 powder-to-water ratio gel being the most homogenous mixture. DOE
also observed that the outer edge on the surface of the gel was
slightly evaporated at the completion of the cooking cycle. In
particular, the gels with a powder-to-water ratio of 1:10 had more
evaporation on the edges than the 1:7 and 1:5 ratio gels, which was
likely due to the larger amount of water making up the 1:10 ratio gels.
DOE also observed, similar to the tests for real food loads, that
when it measured the final temperature of the load after the completion
of the cooking cycle, the temperature continued to rise for 30-90
seconds in most cases before finally leveling off. DOE waited until the
temperature leveled off and used that measurement for the calculation
of the effective heat capacity. DOE recognizes that this may contribute
to additional test-to-test variation depending on the time needed for
the temperature of the load to stabilize for each test. As with the
real food load tests, DOE also noted that it had to conduct a number of
additional retests in cases in which the final temperature was not
within the specified range. DOE similarly recognizes that specifying a
tighter final temperature range than 5 [deg]C for the TX-
151 gels may represent a testing burden due to the difficulties of
achieving a consistent final load temperature from test to test.
Table 16--TX-151 1:10 Ratio Gel Tests
----------------------------------------------------------------------------------------------------------------
Average heat capacity (J/g [middot][deg]C) Test-to-test
Product type Test unit -------------------------------------------- variation--standard
Test 1 Test 2 Test 3 Average error (%)
----------------------------------------------------------------------------------------------------------------
Convection Microwave, Countertop.... 11 33.828 32.448 36.422 34.233 5.89
12 43.748 40.932 39.665 41.448 5.04
13 27.655 29.565 28.127 28.449 3.50
14 54.402 51.997 53.212 53.203 2.26
Convection Microwave, Over-the-Range 15 31.301 32.376 29.910 31.196 3.96
17 34.785 33.503 34.035 34.108 1.89
18 49.865 45.797 44.999 46.887 5.57
---------------------------------------------------------------------------
Average......................... ......... ......... ......... ......... 38.503 4.02
----------------------------------------------------------------------------------------------------------------
Table 17--TX-151 1:7 Ratio Gel Tests
----------------------------------------------------------------------------------------------------------------
Average heat capacity (J/g [middot][deg]C) Test-to-test
Product type Test unit -------------------------------------------- variation--standard
Test 1 Test 2 Test 3 Average error (%)
----------------------------------------------------------------------------------------------------------------
Convection Microwave, Countertop.... 11 34.378 34.588 32.836 33.934 2.82
12 44.150 43.724 42.968 43.614 1.37
13 28.102 28.068 28.381 28.183 0.61
14 48.668 57.097 56.416 54.060 8.66
Convection Microwave, Over-the-Range 15 34.109 27.204 33.126 31.480 11.87
[[Page 33118]]
17 34.850 34.699 34.307 34.618 0.81
18 44.813 43.801 44.559 44.391 1.19
---------------------------------------------------------------------------
Average......................... ......... ......... ......... ......... 38.612 3.90
----------------------------------------------------------------------------------------------------------------
Table 18--TX-151 1:5 Ratio Gel Tests
----------------------------------------------------------------------------------------------------------------
Average heat capacity (J/g [middot][deg]C) Test-to-test
Product type Test unit -------------------------------------------- variation--standard
Test 1 Test 2 Test 3 Average error (%)
----------------------------------------------------------------------------------------------------------------
Convection Microwave, Countertop.... 11 32.798 34.219 31.778 32.932 3.72
12 45.869 45.375 44.995 45.413 0.97
13 30.061 28.882 28.484 29.142 2.81
14 55.433 59.854 48.900 54.729 10.07
Convection Microwave, Over-the-Range 15 27.940 33.899 32.653 31.497 9.98
17 35.116 36.735 36.633 36.162 2.51
18 54.040 46.450 47.023 49.171 8.60
---------------------------------------------------------------------------
Average......................... ......... ......... ......... ......... 39.864 5.52
----------------------------------------------------------------------------------------------------------------
DOE may consider amendments to the microwave oven test procedure
for measuring the convection microwave cooking function for convection
microwave ovens. If DOE determines such test procedure amendments are
warranted, it may consider developing an integrated metric that
incorporates the convection microwave cooking function energy use along
with other active mode and standby mode energy use. As a result, DOE
would require consumer usage data on the number of annual convection
microwave cooking cycles and annual hours spent in convection microwave
cooking mode for convection microwave ovens. However, DOE is currently
unaware of any such data. DOE is seeking comment on the following
issues related to convection microwave cooking.
8. DOE requests comment on the suitability of the various powder-
to-water ratio gels and testing methods (i.e., load temperature
measurement methods, starting and final temperatures, and mass of test
load) described in this section for incorporation into the DOE
microwave oven test procedure for testing convection microwave ovens.
DOE also welcomes comments specifically on the repeatability of test
results presented in this section as well as comments on the
reproducibility of test measurements. In addition, DOE requests comment
on the testing burden associated with these testing methods. When
providing comments, please quantify and describe the associated testing
burdens.
9. DOE requests comment on whether there are any other food load
simulations and testing methods that it should consider for measuring
the energy use of convection microwave ovens. In particular, DOE
requests data and information on the repeatability of such loads and
testing methods.
10. DOE requests consumer usage data on the number of annual active
mode cycles and annual hours spent in microwave-only cooking mode and
convection microwave cooking mode for convection microwave ovens.
E. Convection Microwave Oven Convection-Only Cooking Testing
As discussed above, DOE noted that convection microwave ovens can
also be operated using the convection-only cooking function. DOE
investigated whether a testing procedure could be developed to evaluate
the convection-only cooking function of a convection microwave oven.
DOE developed a testing method based on the DOE conventional cooking
products test procedure for conventional ovens at 10 CFR part 430,
subpart B, appendix I, to measure the energy consumption of the
convection cooking function for convection microwave ovens. The DOE
conventional oven test procedure involves setting the convection
cooking cycle such that the temperature inside the oven is 325 5[emsp14][deg]F higher than the room ambient air temperature. An
8.5 0.1 pound cylindrical aluminum test block is then
heated from ambient room air temperature 4[emsp14][deg]F
until the test block temperature has increased 234[emsp14][deg]F above
its initial temperature. The temperature of the aluminum test block is
measured using a single thermocouple placed at the center of the block
in a 0.08 inch diameter hole 0.8 inches from the top of the block.
Because this test uses only convection heating and is not subject to
safety concerns with arcing from microwave energy, thermocouples can be
used to measure the test load temperature inside the microwave oven
cavity during the test cycle. The measured energy consumption is used
to calculate the cooking efficiency and energy factor.
As discussed above, DOE noted that the convection temperature
setting requirement of 325 5[emsp14][deg]F higher than the
room ambient air temperature would result in a temperature setting
close to 400[emsp14][deg]F. Based on DOE's review of products currently
available on the U.S. market, a number of convection microwave ovens
did not have a 400[emsp14][deg]F temperature setting, but all
convection microwave ovens that DOE surveyed had a 375[emsp14][deg]F
temperature setting. As a result, DOE modified the test method to
conduct this testing using a temperature control setting of
375[emsp14][deg]F to heat the aluminum test block to 234[emsp14][deg]F
above its initial temperature. In addition, DOE also specified that the
aluminum test block be placed on the metal cooking rack provided by the
manufacturer. For each convection microwave oven, DOE conducted three
identical tests to evaluate repeatability of results. The results from
testing, presented in Table 19, showed test-to-test variation ranging
[[Page 33119]]
from 0.68 percent to 2.11 percent, with an average of 1.30 percent.
Table 19--Convection-Only Cooking Test Results
----------------------------------------------------------------------------------------------------------------
Cooking efficiency (%) Test-to-test
Product type Test unit -------------------------------------------- variation--standard
Test 1 Test 2 Test 3 Average error (%)
----------------------------------------------------------------------------------------------------------------
Convection Microwave, Countertop.... 11 7.37 7.24 7.07 7.23 2.11
12 12.48 12.53 12.25 12.42 1.19
13 8.29 8.49 8.32 8.37 1.28
14 10.12 10.06 10.31 10.16 1.32
Convection Microwave, Over-the-Range 15 6.62 6.49 6.43 6.51 1.51
17 11.19 11.05 11.08 11.11 0.68
18 7.60 7.66 7.51 7.59 1.00
---------------------------------------------------------------------------
Average......................... ......... ......... ......... ......... 9.06 1.30
----------------------------------------------------------------------------------------------------------------
If DOE determines that actual and simulation food loads do not
produce repeatable results using the convection microwave cooking
function, DOE may consider developing a test procedure using a single
metric that accounts for the energy use of the different cooking
functions (i.e., microwave-only, convection-only, and convection
microwave cooking) using the microwave-only cooking test method and the
convection-only cooking test method. As discussed above, DOE noted that
the convection microwave cooking cycle for microwave ovens in DOE's
test sample consisted of cycling between microwave-only cooking for 30
percent of the time and convection-only cooking for the remaining 70
percent of the time. DOE may use this mix of microwave and convection
cooking to apportion the energy use measured using the individual test
procedures for microwave-only and convection-only cooking to calculate
the per-cycle energy use for a convection microwave cooking cycle.
However, DOE is not aware of consumer usage data regarding
representative cooking cycle lengths, number of annual cooking cycles,
or annual usage hours for each of the cooking functions for convection
microwave ovens.
11. DOE requests comment on the suitability of incorporating the
convection-only cooking method presented above into the DOE test
procedure for convection microwave ovens. DOE also requests comment on
the potential approach of using the microwave-only and convection-only
cooking tests to calculate the energy use for the convection microwave
cooking function. DOE seeks comment on the repeatability of the
convection microwave oven convection-only cooking function test results
presented in this section. DOE welcomes additional data and inputs on
the repeatability and reproducibility of this convection-only cooking
test method.
12. DOE requests comment on the testing burden associated with
these testing methods. When providing comments, please quantify and
describe the associated testing burdens.
13. DOE seeks comment on the temperature setting of
375[emsp14][deg]F and target final temperature of 234[emsp14][deg]F
above the initial test block temperature and whether such settings
would be appropriate for the DOE test procedure for convection
microwave ovens.
14. DOE seeks consumer usage data on the representative cooking
cycle lengths, number of annual cooking cycles, and annual usage hours
for each of the cooking functions for convection microwave ovens (i.e.,
microwave-only, convection-only, and convection microwave cooking). DOE
also welcomes comment on whether a split of 30 percent microwave and 70
percent convection would be appropriate for apportioning energy use for
the convection microwave cooking function.
F. Cooling Down Energy Use
As discussed above in section 0.0, DOE noted that for all of the
units in its test sample, none contained a fan that operated at the end
of the microwave-only cooking cycle to cool the appliance down.
However, DOE noted that a number of the convection microwave ovens in
its sample had a fan that operated after the completion of the
convection microwave cooking cycle and convection-only cooking cycle in
order to cool the microwave oven. DOE observed during testing that the
cooling down power ranged from approximately 19 watts (W) to 63 W.
Table 20 shows the measured cooling down energy consumption and amount
of time the cooling fan ran after the completion of the convection-only
cooking cycle for the convection microwave ovens in DOE's test sample
that operated a cooling fan after the cooking cycle. These measurements
showed that the convection microwave ovens in DOE's test sample that
operated a cooling fan after the completion of the cooking cycle
consumed between 1.0 Wh and 7.2 Wh. DOE also noted that the amount of
time that the cooling fan operated varied from product to product, and
also from test to test.
Table 20--Convection-Only Cooling Down Energy Use
--------------------------------------------------------------------------------------------------------------------------------------------------------
Test 1 Test 2 Test 3
-----------------------------------------------------------------------------
Product type Test unit Cool down Cool down Cool down Cool down Cool down Cool down
energy use duration energy use duration energy use duration
(Wh) (min) (Wh) (min) (Wh) (min)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Convection Microwave, Countertop............................. 11 ........... ........... ........... ........... ........... ...........
12 1.2 3.22 1.1 2.95 1.0 2.80
13 ........... ........... ........... ........... ........... ...........
14 1.2 3.68 1.3 3.83 1.1 3.48
Convection Microwave, Over-the-Range......................... 15 ........... ........... ........... ........... ........... ...........
[[Page 33120]]
17 6.7 6.52 6.6 6.28 7.2 6.90
18 2.5 3.13 2.6 3.25 2.6 3.27
--------------------------------------------------------------------------------------------------------------------------------------------------------
Note: Test units for which no values are listed indicate that no cooling fan ran after the completion of the combination or convection-only cooking
cycles.
DOE may consider test procedure amendments to include the cooling
fan energy consumption as part of the energy efficiency metric for
convection microwave ovens. If DOE determines that such amendments are
appropriate, it may also consider adjustments to the annual standby
mode hours to account for the additional time that the product operates
the cooling fan at the end of the cooking cycle. The total annual
cooling fan hours would be calculated by multiplying the amount of time
that the cooling fan operates per cycle by the number of total annual
convection microwave cooking and convection-only cooking cycles. These
hours would then be subtracted from the total number of standby mode
hours. However, DOE is unaware of consumer usage data regarding the
total annual convection microwave and convection-only cooking cycles
for convection microwave ovens.
15. DOE welcomes comment on whether the cooling fan energy
consumption should be included in the efficiency metric for convection
microwave ovens.
G. Additional Issues on Which DOE Seeks Comment
DOE may consider amendments to the microwave oven test procedure
for both microwave-only and convection microwave ovens based on the
testing discussed in the sections above. In addition to the specific
issues for each testing method on which DOE is seeking comment, DOE is
seeking comment on the following:
16. DOE welcomes general comments about the potential testing
methodologies to measure microwave oven active mode energy use
presented in this notice. DOE also welcomes comment on any alternative
testing methodologies appropriate for inclusion in the DOE microwave
oven test procedure. DOE requests data on the repeatability and
reproducibility of such testing methods. DOE also welcomes additional
data on the repeatability and reproducibility of testing results using
the test methods presented in this notice.
The purpose of this NODA is to solicit feedback from industry,
manufacturers, academia, consumer groups, efficiency advocates,
government agencies, and other stakeholders on issues related to the
DOE microwave oven test procedure. DOE is specifically interested in
information and additional data on the potential amendments to the
microwave oven test procedure for measuring active mode energy use
presented in today's notice. Respondents are advised that DOE is under
no obligation to acknowledge receipt of the information received or
provide feedback to respondents with respect to any information
submitted under this NODA. Responses to this NODA do not bind DOE to
any further actions related to this topic.
Issued in Washington, DC, on May 29, 2012.
Kathleen B. Hogan,
Deputy Assistant Secretary for Energy, Energy Efficiency and Renewable
Energy.
[FR Doc. 2012-13609 Filed 6-4-12; 8:45 am]
BILLING CODE 6450-01-P