The Physics of Air Conditioners–Preventing bloodshed in the office

air-conditioningAh… Summer time.  Long days, barbecues, and lazy afternoons by the pool.  AND raging office wars over the AC!  AC controls are one of the least understood of all User Interfaces.  This isn’t surprising, as they vary between cars, central units, and window units, and are at times intentionally misleading.  Let me step through a primer to avoid unnecessary battles.

1. The Temperature Setting:  This applies to both window and central air controls.  In window units, it is a gradient from blue to red.  On central units, it is a degree setting in numbers.  Many battles form around a misunderstanding of this control.  Someone will walk into the office, find that it’s hot (because the AC hasn’t been on all night) and flip the temperature control to the “Coldest” setting.  Makes sense right?  Get a quick cool down so it’s livable again?

WRONG:  The temperature control does NOT in fact make the AC shoot out colder air.  ACs are binary objects.  They are either on or they are off.  They ALWAYS shoot out the same temperature of air!  What does the temperature control do then?  That means the AC will continue to run until the room is at the LOWEST possible temperature that the AC’s thermostat allows.  In other words, the AC will just stay on for days and days while it attempts to cool the room to 50 degrees (usually the lowest setting).  Not a good idea!

2. Energy Saver:  Blech!  Who wants to use this secret heat-enhancer guised as an environmentally-friendly control?  No doubt it uses less “cold” energy and once again makes the AC shoot out hot air.

WRONG:  Energy Saver is a stupidly mis-labled feature.  All it actually does is when the compressor (the AC) isn’t running because the room has reached the desired temperature (by intelligently setting the termostat to a human livable temperature), it stops the fan as well.  This way, when the unit isn’t producing cold air anyway, the fan doesn’t continue to run.  This setting should be turned to “off” if you’d like the fan to continue to circulate air or if you hate the fan switching on and off when you are sleeping.  It does NOT affect how cold the air coming from your AC is.

3. The High/Medium/Low Cool setting.  Once again the name explains what this control does.  Obviously on High Cool the AC shoots out “Super-Chilled” air that it generates using cold-enhancing technology.  On Low Cool, it turns off its Super-Chilled air and pumps out luke-warm air befitting a “Low Cool” need.

WRONG AGAIN:  The High/Medium/Low setting only affects the speed of the fan.  On high, the fan spins quickly and will circulate more air as well as creating a stronger “gust” coming from the vent.  On low, the fan spins more slowly and the air flow is reduced accordingly.  Turn it on high if you want to blow the air far and wide and you like the noise.  Put it on low if you don’t like the wind blowing on the back of your neck or would like to have a conversation.

I hope this primer can help alleviate the battles of the knob that often happen in offices.  Although there will always be differences in opinion as to how cool it should be, at least by understanding the AC controls, both parties can have a rational discussion of needs and take the appropriate actions!

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  • Jessica Lowe

    OK, from your totally educational post which leaked out a few of your personal preferences I would like to deduce your air conditioner settings. The best settings in an office which you occupy are 72 degrees, Low Cool, Energy saver ON. However at your home while you sleep you'd like 72 degrees, High Cool, Energy saver OFF. Am I right?

    • drstarcat

      Ha! So wrong. Office: Between 68-72. I'm not religious about this, I just can't STAND when it gets set to 50 degrees and after a few hours I realize that I'm shivering. I don't care about cool setting and probably prefer energy saver on (I never like the on/off thing with the fan)
      Home: 68/High Cool (to drown out the City noise), and ES off (to keep that white noise coming!)

  • Mark J

    Allow me to flash my geek card and point out that the High/Medium/Low Cool settings regarding fan speed are not merely about pushing more air on the back of your neck. Higher fan speeds *heat* up the A/C coil faster because it's "grabbing" more cold air on its way through (resulting in much more condensation at the coil, btw), not unlike a car radiator is more efficient when the car is moving faster, or consider the purpose of a CPU fan….

    • drstarcat

      Duly noted. Thank you!

  • Carmin

    I don't understand the need for an inside temperature that is cooler than you are happy with outside. In my opinion, if you would be comfortable in 80 degrees outside in the park, then the house or work should also be 80 degrees!

    • drstarcat

      Amen to that!

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  • 8000 btu airconditioner

    This article brings me a lot of new knowledge. I usually turned the fan in minimum speed with low temperature ( around 25 c) expected that the conditioner would give maixmum potential of pruducing cold air. But it was wrong!

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    To maintain my air conditioner performance i've tried what people used in tricking the car air conditioner with my room air conditioner. They use pipe wrap to wrap the air conditioner piping and improve the air conditioner performance overall. This will also reduce the electricity bill at the end of the month.

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  • air conditioning duct

    This article is actually kinda funny. I never thought these air conditioners were so complicated. Haha. I guess it’s been a while since I’ve had one. At my mom’s house, I used to just set the temperature of the house and the AC would kick in if it got too hot.

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