This article was originally published in the January/February 1993 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.
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Home Energy Magazine Online January/February 1993
SPECIAL SECTION ON REFRIGERATORS
MAINTENANCE DOESN'T NECESSARILY LOWER ENERGY USE
Utility bill stuffers direct customers to clean their refrigerator coils in order to save the customers a few dollars and the utility companies a few power plants. While cleaning coils is a nuisance, the result, claim the stuffers, is a more energy-efficient refrigerator whose maintenance costs will soon pay for themselves through reduced utility bills. The question is, do the savings even pay for the coil brush? Recent studies challenge the conventional wisdom that refrigerator maintenance, from coil cleaning to gasket replacement, leads to lower energy use. Studies indicate that there is actually little, if any, decrease in energy use resulting from maintenance.
The most detailed study was conducted by Rochester Gas and Electric (RG&E) between January 1988 and September 1990. RG&E monitored field energy consumption of 70 refrigerators every 30 minutes. In October 1989, a contractor visited 27 of these homes and performed maintenance measures on the residents' refrigerators, such as replacing all gaskets, cleaning the condenser coils, and fixing any other obvious problems. After maintenance, RG&E continued monitoring these refrigerators for another year, after which they replaced most of them with new energy-efficient units for the next phase of the study.
A small decrease appeared in summer energy use after maintenance, but over the year, the average annual energy use of the 27 refrigerators actually increased by 50 kWh per year, or 2.5%. The small difference in energy use might be attributed to year-to-year variations in outside temperatures. Only three of the 27 units showed a clear drop in energy use after the servicing. Two showed a clear increase. The rest of the units appeared unaffected by the repairs.
At maintenance time, the average age of the 27 refrigerators was 16 years. We could not find the labeled consumption for many of these units, but, based on the data obtained in the first year of monitoring, as a group, these units consumed more energy than would have been expected for new units built 16 years earlier. The 1973 unit energy consumption was 1,700 kWh per year, while in 1988, when they measured them, these refrigerators consumed an average of 2,100 kWh per year. Thus, it appeared that degradation had occurred over time, and we expected that maintenance would return the group's aggregate energy consumption closer to the 1973 value.
The absence of any aggregate energy savings isn't so surprising in light of the maintenance performed. The contractor found that only 10 of the 27 units actually needed their coils cleaned. (All the others were clean.) Twenty-four of the 27 units received new gaskets. (Even if the gaskets were in good condition, they were replaced.) Gasket replacement caused new problems, such as a door failing to close. (On this unit, the old gaskets were reinstalled.) The contractor was reluctant to remove the old gaskets from two units because they appeared to be holding the door together. The contractor also identified and repaired other obvious mechanical problems. For example, in one case the contractor re-connected an evaporator fan motor and in another case cured an overheating compressor. In five cases, the air flow in the condensers was severely restricted.
Even if maintenance did not improve the aggregate energy consumption of the group, it was expected to improve the efficiency of some refrigerators--those most in need of maintenance. We checked to see if the units with plugged condensers saved energy as a result of maintenance. In five cases, the condensers were plugged. Of these five units, two had marked decreases in energy use after maintenance, and the other three units showed no such decrease. All units with plugged condensers had the coils mounted on the bottom.
RG&E charted daily energy consumption of three units for 90 days before and after maintenance (see Figure 1). Unit 1 had no problems discovered, although new gaskets were installed. The decrease in energy use over time does not appear related to the maintenance done, and is representative of a seasonal pattern seen for most units. Unit 2 had no problems discovered although new gaskets were installed. Unit 3 is one of the few in which decreased energy use was clearly related to the clearing of a plugged condenser.
Philadelphia Electric Co. (PECO) undertook a more modest study than RG&E but came up with similar results. PECO monitored five refrigerators in ordinary kitchens for two weeks before and after coil cleaning. Initially the units consumed 4.8 kWh per day. After coil cleaning, electricity consumption fell about 5%, or .23 kWh per day. PECO did not monitor long enough to determine if the savings persisted because they quickly moved into the second phase of their experiment--replacement of the old units with new, efficient ones. According to Kathleen Behr of PECO, the new refrigerators used about 2.3 kWh per day, more than a 50% reduction. Behr feels that a refrigerator replacement program is a more effective way to reduce energy use than is maintenance. We conclude that cleaner coils don't always lead to leaner bills. --Barbara Litt, Andrew Megowan, and Alan Meier
Barbara Litt and Andrew Megowan are research assistants at the Lawrence Berkeley Laboratory. Alan Meier is executive editor of Home Energy.
Figure 1. Energy Consumption 90 Days Before and After Maintenance
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