This article was originally published in the May/June 1993 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.



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Home Energy Magazine Online May/June 1993




Don't Make Fridges Like They Used To

Loved your special refrigerator issue (HE, Jan/Feb '93). With regard to old refrigerators, a distinction should be made for very olde boxes which are quite efficient. I have two old boxes still running, a GE and a Westinghouse. Each uses less than 15 kWh per month (180 kWh per year). One uses sulfur dioxide as the refrigerant. In your pictures I don't see any boxes this old, so they must be getting rare!

Thick insulation, efficient and massive compressors, and oversized condensers help as does the small U-type, in-box freezer compartment. These boxes have the rounded-off top styling and probably date from the late '20s or '30s.

I once took a more modern Frigidaire 14ft2 no-frost box and modulated the power to the whole box with a close hysteresis temperature control in the freezer set at 8-10Fdeg.. This lowered the average condenser temperature; cut the power to door heaters, defrost motor, and interior light; and lengthened the time between freezer defrosts. The power consumption dropped from 116 kWh to 77 kWh per month.

The motor started more often and occasionally ice built up inside the refrigerator as the close cycling gave it little time to melt. This experiment led me to believe that considerable savings could be had by changing controls. With intelligent ice sensing to regulate defrosts and high thermal mass and surface area in the condenser, a great deal is saved.

Boulder, CO


More Dirt on Coil Cleaning

I want to congratulate you on the special refrigerator issue. It's very good, informative fun reading, and full of surprises. (The lemon where they empty the freezer of ice every morning is a great example.) I'm especially curious about your article on maintenance not necessarily lowering energy consumption (Maintenance Doesn't Necessarily Lower Energy Use, HE, Jan/Feb '93, p. 17).

Is the figure correct that only 10 out of 27 refrigerators had dirty coils? This is very surprising. In my informal research, everyone I have ever asked has never cleaned their coils. Do you know whether the owners cleaned them, or if the design somehow didn't collect dust? (Judging from the average age of 16 years, I assume it wasn't just that they were too new to be dirty.)

What do you suspect was going on in the two units that showed a marked increase? I assume someone checked that the new gaskets were properly installed. Is it possible that the repair person lowered the thermostat setpoint from a temperature which was previously too high? (Did he or she also possibly raise it in some of the cases where energy was saved?)

Prof. George W. Hart
Department.of Electrical Engineering
Columbia University
New York, NY


Co-author Barbara Litt replies: The figure is correct. We were also surprised. Here are the details.

The contractor noted the condition of the condenser coils, classifying them into the following subjective categories:<


14 were clean,
1 was no dust,
1 was good,
1 was average,
4 were fair,
1 was dirty, and
5 were plugged.


The repair visits were made by one of two people, and it is possible that they did not use identical judgments. In summarizing this work, we lumped fair, dirty, and plugged into the category of needing the coils cleaned, and the rest were considered clean. Of course, the actual condition of the coil deemed average could have been dirty, but this would not substantially change the conclusion. We do not have any information about whether the owners cleaned the coils, nor about designs that didn't collect dust.

While the increased energy use began immediately after maintenance, and probably resulted directly or indirectly from the maintenance, it has not been possible to identify the actual physical cause of the increased energy use. The contractor may have adjusted the thermostat setpoint without noting that this had been done. The occupants could have adjusted it after maintenance and we would be none the wiser. One of the units with increased use had new gaskets which caused the door to pop open. The old gaskets were reinstalled the next day, but perhaps were no longer in good condition.

Whole-House Fans and Oil-Fired Furnaces

We have a dilemma that nobody else seems to recognize (or admit), and I'd like to know if I'm worrying too much. We are having a new house built, and one of the features being added is a whole-house fan. Our dilemma is that the hot water system is a tankless in-furnace unit, which means that to make hot water, the furnace comes on. Why is that a problem? Well, the whole-house fan will very effectively suck all those furnace gases back down the chimney and into our house. The obvious answer is to spend money and have a gas or electric water heater hooked up for use during the fan seasons, but that is expensive.

Does anyone have both a whole-house fan and a furnace-fired hot water system? If so, can you detect any gases when both are running? Is there something that can be done to keep the gases from being sucked in?

It won't be practical, or effective, to keep the basement door shut and a window open, so that's out. Any other (inexpensive) ideas? The reason I ask this question is that in my last house, I was actually awakened in the middle of the night by the smoke alarms when a fan and furnace were on at the same time. The smoke was very thick in the basement by the time I turned off the fan and furnace.

Greg Roody
Shrewsbury, MA


P.S.--The solution we came up with was to wire the fan so it would shut off when the furnace comes on. It's not at all annoying; we don't even notice it anymore.

Editor's Note: Whether a whole-house fan will produce backdrafting problems depends on a number of factors including the type of combustion equipment, how much depressurization the fan achieves, and the extent of coupling between the occupied space and the space with the equipment. The normal use of such fans involves opening one or more windows, to get the maximum amount of air moving through the house--otherwise the depressurization could easily result in unsafe operation of combustion appliances. Your interlocking solution solves that safety problem, but the effectiveness of the fan is still compounded by lack of free air flow. Perhaps the addition of dampers would solve both problems (see Backdrafting Causes and Cures, HE, May/June '91, p. 30).

Performance Contracting Full of Bull?

Gil Peach's performance contracting article fails to recognize that a utility promoting DSM is always interested in obtaining the lowest cost of delivered capacity savings (see Performance Contracting: Advice to Utilities, and related, Performance Contracting: An ESCo Perspective, HE, Nov/Dec '92, p. 19 and 23, respectively). Bidding programs therefore promote cream skimming since lowest cost is paramount, even though this is not in anyone's interest. To protect against cream skimming and lost opportunities, the utility does not need to expand its staff to monitor the retrofit process, but rather it needs to design sound DSM programs which encourage energy service companies (ESCos) to complete comprehensive installations!

Advocating that utilities avoid front loading is really ludicrous. The very idea of DSM programs is to incentivize the market. That is achieved through education or money, up-front, when the resources are being expended.

Defining baseline measurements using only one year is probably not a more prudent approach. An average of several years is more apt to reflect normal energy consumption figures unless changes in equipment or use have occurred. Also, payments made on batches of customers is the only way to reduce person-months of effort in paying for completed small capacity jobs.

Adjusting for free riders is justified; however my experience suggests that there are as many customers who are incentivized by neighboring projects (utility subsidized projects) as there are free riding. These free-drivers should also be accounted for.

In the marketplace customers typically have a much higher cost of capital than utility companies and therefore they require a higher rate of return on conservation DSM projects than the utility. The goal of a DSM program is to buy down the cost to the customer of a conservation project (with utilities paying up to avoided cost).

James C. Crossman
Financial Energy Management, Inc.
Denver, CO


Author Gil Peach responds: The added cost for a performance contractor over the time and materials contractor is risk payment--compensating the performance contractor for accepting the risk of failing to produce the expected result. In theory, strict inspection and verification protocols protect a utility from paying for phantom savings. Be aware that in both negotiations and in ongoing work, performance ESCos use many imaginative strategies to weaken inspections, evaluation, and verification.

To say that a utility promoting DSM is always interested in obtaining the lowest cost of delivered capacity savings doesn't acknowledge other objectives of a conservation project: the quality of work, materials, and customer service; the comprehensiveness and persistence of measures; and the relationship of the project to the overall strategic business plan of the utility. Although the advantage of hiring the performance contractor seems to be a simplified package, the utility may end up shouldering unexpected costs of staffing and consultants to handle problems in verification of energy savings.

Also, an important drawback of front loading is that the utility can find itself trying to recoup money from a defunct energy services company (ESCo) after savings have disappeared.

Mr. Crossman is correct that averaging years of energy savings may provide a more representative baseline than one year. But be aware that performance ESCos can use this argument as an opening to create fradulent baselines from which to measure their performance. Likewise, batching can be a convenience for both parties, but it can also be set up to burden a utility's oversight capability.

Free market economics are largely illusions in this sector of DSM conservation if there aren't numerous buyers and sellers. While it is possible for utility-performance ESCo partnerships to be worthwhile, given current regulatory realities and dollar amounts involved, they are also vulnerable to fraud.

Author Greg Thomas also responds: Mr. Peach's arguments can be taken as justification for utilities' limiting competition to their own programs from ESCos. Regulators need to understand that kind of competition--and among ESCos as well--and work toward fostering utility-ESCo cooperation. The heart of the problem is the lack of standardized processes and criteria for the equal evaluation of DSM programs carried out by both utilities and ESCos. Friction develops when utilities apply criteria for persistence and quality to ESCo programs that they do not apply to their own. Also, when utilities are given short-term rewards for program implementation, without measurement of persistence, installation quality, and comprehensiveness, they will tend to commit the same abuses as ESCos.


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