I questioned my neighbor why he does it. He said that his father always told him to.
What my neighbor's dad told me may seem correct. Through my scholarship I have learned that the presumption is probably incorrect.
The outdoor part of a central air-conditioning system moves heat from homes into the outdoors.
They are usually about the size of a garbage can, but can be as small as a bucket or as big as a fridge. Most of them are exposed to the elements. They transfer heat to the air. Tubes that carry the hot refrigerant give off heat when it gets cold.
Dust and grass clippings tend to accumulate on the coil surface. Most people think that this stuff slows down the passage of heat from inside to outside. The system's ability to expel heat is restricted by any debris that accumulates.
We set out to find out the extent to which dirty air conditioners are less efficient than clean ones. Many of the other experts were surprised by what we found.
The previous work used reduced air flow as a proxy for the effects of dirty coil dirt in a laboratory setting. Although it is necessary to carefully control operating conditions, we took a novel approach by collecting condensers that had gotten dirty through ordinary residential use and bringing them to the lab for study.
They were covered in real-world dust and other particles on a daily basis. After testing the air conditioners, we washed them with a garden hose. The coil cleaning fluid was tested for a third time.
It was surprising to find that dirty air conditioners perform better than clean ones. There was a 7 percent increase to a 7 percent decrease in the performance of the coil we tested. None of the changes was significant.
The coil that registered a 7 percent improvement was dirty with 7 grams of dirt per square foot. The dirtier coil had 17 grams of dirt per square foot. It was so filthy that it was almost impossible to see the fins before we washed it. In the lab, most of the coil were clean.
We did more testing to see how dirty the equipment was.
The accumulated dirt stirs up the air as it passes over the coil. These small gusts can transfer heat away from the coil. This can cause the equipment to perform better when it is dirty. Even though the dirt has reduced the air flow, this is still true.
You might be wondering if you should wash your own condenser if your home has one. What should you know?
It might be a good idea to clean your air conditioner. It may make things worse. It probably won't change anything. Unless the coil is dirty, I believe in skipping this task. If it makes you feel better, hose it down. That is what I intend to do from now on.
It is difficult to let go of deep-held beliefs, whether it is that diet makes you lose weight in the long run, or that home maintenance is justified. I am bracing for some unpleasant responses from people who might lose out if the business dries up because they refuse to accept that there was no basis for the conventional wisdom.
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David Yuill was the writer.
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