Recently, a college engineering professor reported, “we found that dirty air conditioner condensers often perform better than clean ones.”
Are you kidding me?
Early in my career I was one of the charismatically challenged. I worked as an engineer for the Turbo Refrigerating Company and for Lennox Industries. Granted, I was a mediocre engineer, which explains my move into marketing, where I got to tell engineers what to design. The point is, as a recovering engineer, I know the breed. As the saying goes, “you can always tell an engineer; you just can’t tell one much.”
Engineers are stubborn creatures. Even when they think they might be wrong, they often struggle to admit it. For example, the engineering professor who performed a study on coils and found that cleaning them makes no difference ended his piece by stating, “As news of our findings spreads, I’m bracing for some unpleasant responses from people who might lose out if the condenser-cleaning business dries up and others who simply refuse to accept that there was no basis for the conventional wisdom on this question.”
The people who will lose out if the condenser cleaning business dries up are the poor homeowners who end up skipping maintenance, paying higher than necessary electric bills, suffering more frequent breakdowns, losing cooling capacity over time, and ultimately replacing sooner than otherwise necessary. How can this be if maintenance makes no difference? It’s because maintenance does indeed make a difference and numerous research studies show it.
For example, the EPA reported that “a buildup of just 1/100th of an inch of dirt or film on an evaporator coil can reduce its efficiency by 5 percent.” Moreover, “a buildup of .042(1/20) inches of dirt on the heating or cooling coil can result in a decrease in efficiency of 21 percent.”
According to the U.S. Department of Energy, “a dirty condenser coil can increase compressor energy consumption by 30 percent.”
The research isn’t limited to the U.S. HVAC HESS (The Heating, Ventilating, Air-Conditioning High Efficiency Systems Strategy) is a 10-year study performed for the Australian government. It found, that “systems whose heat transfer surfaces have not been cleaned in the last three years an immediate energy saving of at least 10 percent is expected to be achieved following cleaning.” They further reported, “A rise in condensing temperature from 35 to 40C as a result of dirty coils can cut cooling capacity by 7 percent and increase power of 16 percent.”
According to the Airguard Research and Technical Center, a “moderately dirty” coil increases electricity use 39 percent for a 3-ton and 47 percent for a 5-ton system.
The research is not limited to government work. In 2014, 636 tune-ups were performed in Arkansas under the utility sponsored CoolSaver program, which resulted in EER increases of 13 percent to 18 percent. Over 2011 to 2015, 16,200 tune-ups were performed in south central states, resulting an 11 percent to 15 percent EER increases.
According to the Airguard Research and Technical Center, a “moderately dirty” coil increases electricity use 39 percent for a 3-ton and 47 percent for a 5-ton system.
A product manager for Nu-Calgon noted in a trade magazine article that, “Dirty condenser coils increase power costs. When the coil becomes fouled with dirt and grime, it cannot provide adequate or designed heat transfer. The soil’s insulating effect causes higher discharge pressure. The higher discharge pressure increases amp draw and run time of the compressor, at the same time reducing capacity. Equipment operating with dirty coils may use as much as 37% more energy than equipment with clean coils.”
The list does not include the many studies by Proctor Engineering for PG&E, Florida Solar Energy Center research, the Texas A&M research into the impact of dirty blowers and undercharged systems, the original LSU research on maintenance, Honeywell research on the impact of coil cleanliness, and so on. In short, every other empirical study shows that dirty coils cost energy and tune-ups pay for themselves. It is not merely “conventional wisdom.”
Frankly, it just makes sense that clean coils outperform dirty coils. It’s intuitive. A fouled heat transfer surface will transfer heat less efficiently than a clean one.
Of course, a stubborn engineer will insist that everyone else is wrong. Does it matter? It does when the engineer writes for the layman, places it in the public domain, and his work gets copied and shared hundreds of times.
Frankly, it just makes sense that clean coils outperform dirty coils. It’s intuitive. A fouled heat transfer surface will transfer heat less efficiently than a clean one.
It’s up to you to communicate the correct message that maintenance makes sense from an economic (lower utility bills), environmental (less powerplant emissions), comfort (restored capacity), and convenience (fewer breakdowns) perspective. It’s up to the owners of the research studies to repackage their results in a consumer-friendly form and make these results readily available. Will they?
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