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Wed, Feb. 19

Turn off your ceiling fans to save energy: Air conditioners vs. evaporative coolers, part 2, plus ceiling fans

Last time I wrote about evaporative coolers. I had the usual supportive feedback, such as these two.

Q: Randy, in your May 9 column you answered a question about evaporative coolers. You told us how wonderful they are, how well they work, and that they are less expensive to operate than central air conditioners. You said that having central air conditioning and an evaporative cooler is "the best of both worlds."

A: I'm glad you love evaporative coolers so much, and I'm for saving energy, but you need to be a little more objective. You forgot to point out that operating the evaporative cooler with one large vent 1) makes the house very dirty, 2) makes the house very humid, and 3) is so loud you can't hear the TV if the cooler blower is on high speed.

Q: Our home had both central air conditioning and a roof evaporative cooler with one large vent in the living room. We used the evaporative cooler for about a week the first summer and then had it (and the ugly vent) removed. I'm willing to spend a little more to have a comfortable, clean home. Amanda in Prescott.

A: Amanda, thank you for completing last week's column for me. You may not believe this, but I actually had a paragraph written that said some people don't like evaporative coolers for the reasons you stated. But, alas, I ran out of room in that column. Since all the paragraphs in my columns are packed full of exciting, useful information, it was hard to pick one to leave out.

I tend to agree with you, I don't like the high humidity in my house. 20 years ago, we had a home with no air conditioner, just an evaporative cooler. My printer used regular (stacked) copy paper, but the humidity made it come out looking like it was from a roll like those old fax machines.

Q: Randy, in your column today you stated having air conditioning and an evaporative cooler could save energy. I was a heating contractor for many years. An evaporative cooler will greatly increase the humidity inside a home. An air conditioner is a dehumidifier. So, every time you operate an evaporative cooler, it will take the air conditioner longer to cool the home because of the humid air. Constantly switching between the evaporative cooler and air conditioner is not energy efficient. We removed the evaporative cooler and installed ceiling fans in every room. We leave the thermostat at 78 and run all the fans all the time to save energy. Peter in Paulden.

A: Paulden Peter, you are totally correct. And totally incorrect. I recommended using the evaporative cooler when it was not monsoon season and not 95 degrees. I never recommended 'constantly switching' between the air conditioner and evaporative cooler. I agree, that would not be very efficient, or convenient.

However, leaving a fan on when no one is in the room wastes energy. Read any ceiling fan box in a big box store. They have an 'efficacy' label required by the government. Don't get me started on that. The Government has not ruined enough appliances with silly regulations and requirements, now they're attacking ceiling fans. The efficacy is, simply put, the airflow per watt, measured in Cubic Feet per Minute per Watt. This is kind of like the miles/per/gallon in your car. Except mph is useful, and ceiling fan efficacy is not.

But anyway, when you read a ceiling fan box, they all have a comment such as "Money Saving Tip: turn off fan when leaving room." A fan cools you with a breeze. If it's 100 degrees outside with no wind, you feel 'hotter' than if there is a breeze. The same is true with a ceiling fan. A fan does not lower the temperature of a room at all. It lowers your temperature by 'blowing' over you and removing heat.

And in case you want to argue with me, I must warn you that I have an infrared camera. I can show you how hot ceiling fan motors get, easily over 100 degrees. So technically operating a ceiling fan will slightly increase the temperature in a room. If you are in the room, the breeze will cool you. If you are not in the room, you are wasting energy. First, you're wasting electricity by running a motor/fan that is not accomplishing anything in an empty room. Second, you are adding some heat to the room that the air conditioner will have to compensate for.

So let's go back to that 'efficacy' thing again. Stating how much air is moved per watt is incomplete information. There are other things that affect how well a ceiling fan will work. It may be better to compare the efficacy with the cargo capacity of a truck rather than the miles per gallon. A small truck can haul a 1000-pound load and a large truck can haul 2000 pounds. Similarly with fans, size is very important. (Insert 'size' joke here). A larger room needs a larger fan. By larger we mean the blade diameter, a common one is 52 inch. But there are much smaller fans. A smaller fan will have a much lower efficacy rating. But in a small room, a small fan may be more efficient than a large fan. Using the truck analogy, if you never have to haul more than 1000 pounds why buy a truck that can haul 2000 pounds but costs more to operate?

And if you plan to install a fan near the ceiling in a room with 30-foot high ceilings, forget the miles per gallon. You want the big block turbo with dual exhaust to move as much air as possible, not the highest 'airflow per watt'.

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