EnergyStar freezer ave power measurement

[gar]

111211-1442 EST

I am looking for one or more persons that have a Kill-A-Watt EZ (model 4460), a moderately new upright freezer of about 20 cu-ft, operating at about 0 deg F internal and 70 deg F ambient, and know what was the Energy-Star kWh per year rating on the yellow tag on the freezer.

If you fall in this category I would appreciate having you run an experiment to see what is the actual consumption. A non-EZ is probably not adequate for the experiment because it looses data on small power interruptions.

Freezers and refrigerators have a long cycle on-to-off-to-on, like 1 to 2 hours. The test needs to be done over maybe several days to a week when nothing new is added to the freezer. A few door openings and removal of contents won't have much effect on energy consumption. Putting new room temperature stuff in the freezer has a noticeable effect, already frozen stuff no problem.

The time to run the test is determined by desired accuracy and how well data measurements can be synchronized with the compressor start time. Ideally one wants to measure energy input from one start time to an Nth start time. This provides an equal number of on and off periods for the test time.

Suppose the test is run over a 1 day time period and the freezer has a total on-off cycle of 2 hours and the duty cycle is 50%, then a maximum error of 1/24 in time might occur leading to an error of 24/23 - 1 = 4.3% in the calculated average power consumed. Four days reduces this error to about 1% and averages other variables.

See:
http://www.consumersunion.org/pdf/DOE-comments-1-15-10.pdf

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[Besoeker]

111211-1442 EST

I am looking for one or more persons that have a Kill-A-Watt EZ (model 4460), a moderately new upright freezer of about 20 cu-ft, operating at about 0 deg F internal and 70 deg F ambient, and know what was the Energy-Star kWh per year rating on the yellow tag on the freezer.

If you fall in this category I would appreciate having you run an experiment to see what is the actual consumption. A non-EZ is probably not adequate for the experiment because it looses data on small power interruptions.

Freezers and refrigerators have a long cycle on-to-off-to-on, like 1 to 2 hours. The test needs to be done over maybe several days to a week when nothing new is added to the freezer. A few door openings and removal of contents won't have much effect on energy consumption. Putting new room temperature stuff in the freezer has a noticeable effect, already frozen stuff no problem.

The time to run the test is determined by desired accuracy and how well data measurements can be synchronized with the compressor start time. Ideally one wants to measure energy input from one start time to an Nth start time. This provides an equal number of on and off periods for the test time.

Suppose the test is run over a 1 day time period and the freezer has a total on-off cycle of 2 hours and the duty cycle is 50%, then a maximum error of 1/24 in time might occur leading to an error of 24/23 - 1 = 4.3% in the calculated average power consumed. Four days reduces this error to about 1% and averages other variables.

See:0
http://www.consumersunion.org/pdf/DOE-comments-1-15-10.pdf

.

An energy meter might be a better way to go but I still think there are just too many variables to draw firm conclusions.
Take stuff out, put stuff in, maybe non constant ambient (turn down the heating at night?) warmer or cooler days....

 

[mivey]

I do have a 4460 but can't match your temperature requirements due to the season. I can offer readings from a frequently-opened indoor-ambient over-under fridge.

With an outdoor-ambient (garage ambient), I can offer an occasionally opened chest freezer, an occasionally opened over-under fridge, and an occasionally opened upright freezer.

If any of those will help your analysis, let me know and I'll be glad to gather the data.

 

[gar]

111211-1936 EST

Besoeker:

The Kill-A-Watt 4460 is an energy meter. It measurement capabilities are:

Volts, amperes, watts, volt-amperes, frequency, power factor, time power is present since last reset (modulo 10000 hours), and kilo-watt-hours since last reset (0.01 to 9999),

This measures RMS values and does a good job on power measurement over the 0 to 1 PF range. All for $30. More than sufficient in accuracy for most homeowner experiments.

There is no need to evaluate cool down and door opening effects to determine a relative efficiency of a referigerator or freezer. The primary concern is heat loss from the box, and efficiency of the cooling system. To make comparisons of one model vs another the steady-state conditions seem like the most important criteria.

Comparing a chest freezer with an upright probably requires some algorithm for door openings. It is also true that a heavily insulated box vs one lightly insulated might require separate analysis of the cooling system.

But what I am trying to find out here is how do Energy-Star ratings on the freezer label compare with actual use at 0 deg internal and about 70 deg ambient. In other words should a customer expect to get some results similar to what is advertized? Or does the customer need to try to do their own testing before purchase? If that would even be possible?


mivey:

Your garage upright might provide some interesting information.

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[mivey]

111211-1936 EST

mivey:

Your garage upright might provide some interesting information.

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I'll put it on and let it run for a few days.

 

[gar]

111211-2057 EST

My Admiral upright is about a 16 to 18 cu-ft unit and has an average power consumption of maybe 140 W at moderate weather conditions. The external box size is about 30 x 27 x 65 = 52,650 cu-inches or 30.5 cu-feet. My Amana is about 32 x 27 x 69 = 59,616 cu-inches or 34.5 cu-feet. This one is probably about a 20 cu-foot unit.

See http://beta-a2.com/EE-photos.html for photos of power vs time at the end of the web page and numbered P29 and P30 for the Admiral upright freezer.

A new GE FUM21SVRWW 20.6 cu-ft manual defrost is listed as 526 kWh per year. Average power is 60 W. No test specifications, or whether it can operate in 0 deg F weather. At my rates this is $68/year. Cost of the Admiral is 1227 * 0.13 = $159/year. The difference is 160-68 = 92. The new GE cost is 656 at Home Depot. Payback about 7 years if it really is 60 W average for consumption.

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[mivey]

20.6 cu ft, 2006 model
Yellow tag: 769 kWh/yr, similar units 745-763 kWh/yr, $64/yr@8.29?/kWh

Data so far:
46:27 hours, 2.96 kWh

I would guess average ambient around 55-60?F

Will report back in a few days.

 

[gar]

111213-2346 EST

mivey:

That looks very good. About 64 W average power, and 560 kWh per year. Better than the yellow tag.

Is your average internal temperature 0 deg F?

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[mivey]

111213-2346 EST

mivey:

That looks very good. About 64 W average power, and 560 kWh per year. Better than the yellow tag.

Is your average internal temperature 0 deg F?

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-5?F
94:11 hours, 6.34 kWh

Ambient has warmed up the last couple of days, probably a good 10-15 degrees. Door has been opened about 4-5 times over the last two days (1 time on previous measurement).

 

[gar]

111215-2109 EST

mivey:

Thanks again. The results are very good, about 67 W average.

I do not think that door openings are a real big factor for refrigerators and freezers unless one has to do all their thinking after the door is open. There is not much thermal mass in air and I have looked at some of my refrigerator openings and many are 4 to 6 seconds long. Freezer is probably somewhat longer to search for a lost item.

What is the brand of your freezer and does it have auto defrost?

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[mivey]

111215-2109 EST

mivey:

Thanks again. The results are very good, about 67 W average.

I do not think that door openings are a real big factor for refrigerators and freezers unless one has to do all their thinking after the door is open. There is not much thermal mass in air and I have looked at some of my refrigerator openings and many are 4 to 6 seconds long. Freezer is probably somewhat longer to search for a lost item.

What is the brand of your freezer and does it have auto defrost?

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Kenmore with auto defrost

 

[mivey]

FWIW,

I put a thermometer in the freezer last night. It read -10?F this morning.

 

[bob]

-5?F
94:11 hours, 6.34 kWh

Ambient has warmed up the last couple of days, probably a good 10-15 degrees. Door has been opened about 4-5 times over the last two days (1 time on previous measurement).

Is your rate 6.34 cents per KWH? What neighborhood is that?

 

[gar]

111216-2150 EST

mivey:

With -10 F internal and 50 to 60 ambient that is probably similar to 0 and 70 F. However, Consumer Reports indicates that the The Energy Star specification for testing at 90 F ambient may not be a good predictor of 70 F operation. Your results are certainly in line with the Yellow Tag.

If the Kill-A-Watt is still connected could you check power and PF while the compressor is running and after power has leveled off. See my site photo P 29 http://beta-a2.com/EE-photos.html for my freezer power vs time curve. Note the substantial drop in power vs time. My refrigerator has a more flat curve.

 

[mivey]

It is still connected. I'll have a look later.