How It Works: Air Conditioner

Depending on what climate you live in, you may be experiencing extreme “dry heat” right now or the kind of temperatures made even more uncomfortable by the addition of high humidity levels. However unbearable the temperature might be outside, that window or wall air conditioner can make a big difference when relaxing inside on a hot afternoon or attempting to get a good night’s sleep when the outdoor thermometer says it’s still close to 90 degrees Fahrenheit. Of course, we didn’t always have it this easy…

A refreshing invention

Looking back at the history of air conditioning, we can see that most North American homes had no air conditioning at all until the second half of the 20th century. This was primarily due to how large and pricey air conditioning systems were until heating and cooling companies were able to manufacture more compact units in an efficient enough way to lower the unit’s cost.

The idea behind air conditioning can be traced all the way back to 1758 when that inventive founding father Benjamin Franklin joined forces with a Cambridge University chemistry professor named John Hadley. The two men came up with a theory that an object, person, or space could be quickly cooled using the principle of evaporation, creating heat loss through evaporating liquids.

But it wasn’t until 1902 that Willis Carrier designed a mechanical system that blew air through water-cooled coils in order to control humidity in his printing shop. The idea was to keep the paper in the shop dry to avoid the print becoming smeared, but employees in the shop remarked how much more comfortable they felt when the system was running which increased the potential for Carrier’s invention. Eventually, Carrier joined forces with six other engineers to form the Carrier Engineering Corporation with the intent on building cooling systems for public buildings.

By 1929, the Frigidaire company came up with a way to adapt refrigerator technology to create an air conditioning system small enough for home use, but the expense of the system resulted in low sales when the unit debuted in 1932. It wasn’t until 1947 that an inexpensive version of the window air conditioner went on the market and, finally, the use of indoor home air conditioning became increasingly popular. While central air cooling systems have become the standard in new homes, the simpler and less expensive window or wall air conditioners continue to bring relief to millions.

How does an air conditioner keep me cool?

So, how does a modern-style window or wall air conditioner do its job of keeping you cool?

When you turn the air conditioning unit on, the thermostat control sends 120 or 220 volts of alternating current to the compressor and fan motor. The compressor acts as a pump, compressing refrigerant in gas form into the condenser coils, located near the back of the unit, where the gas is condensed into a hot liquid. The condenser coils dissipate the heat as the liquid travels through them. Once the refrigerant has passed through the condenser coils and a capillary tube, it travels to the evaporator coils located near the front of the unit. As the refrigerant enters these coils, it expands back into a gas which makes the coils cold. The gas flows through a suction line attached to the compressor which will then compress the gas back into the condenser coils so the cooling cycle can continue.

As the refrigerant makes its way through the compressor, condenser, and evaporator, the fan motor rotates a blower wheel which draws in air to be cooled by the evaporator coils before recirculating the air back into the room. The same motor also operates a condenser fan blade which draws outside air through the condenser coils to cool them.

The air temperature is regulated by a thermostat control. Depending on the model, the control may be a thermostat switch and sensing bulb assembly or an electronic control board that works with a sensor. The sensing bulb or electronic sensor is clipped to the front of the evaporator to monitor the temperature of the air entering the coils. Once the room has sufficiently cooled, the thermostat control will shut off the voltage to the compressor.

Some models which use a vent may be able to just run the fan motor in order to draw in cool night air if this option is desirable. However, when the unit is actively cooling the air, the vent must be closed for the system to work properly.

Due to the evaporation process, it’s normal for water to collect in a condensate pan at the bottom of the air conditioner when running. A slinger ring on the condenser fan blade picks up this water and sprays it onto the condenser to help the coils dissipate the heat. To prevent the water from dripping out of the front of the unit, the air conditioner should be tilted back slightly when installed in a window or wall sleeve.

Why is the air conditioner not keeping me cool?

Have you been patiently waiting for your air conditioner to cool the room, but you don’t seem to be getting any relief? Here are a few potential answers for why that is, plus some troubleshooting and maintenance steps you can take:

  • If you can hear the air conditioning unit running, but the air doesn’t seem to be recirculating, the fan motor has likely burned out and will need to be replaced.
  • If the unit is only blowing hot air out the front vent, the compressor may have failed, or the refrigerant may have leaked out of the system. It is recommended that only licensed technicians perform refrigerant system repairs, due to the specific skill (and the expense of the tools) required to do the job right.
  • If you suspect that the air conditioner is not cooling the air properly, you can use a common thermometer to help determine the cause. Allow the air conditioner to run for fifteen minutes, then measure the temperature of the air in the room as well as the temperature of the air exiting the cooling vent. The difference in temperature between the room air and the cooled air should be fifteen degrees Fahrenheit or more. If the difference is less than fifteen degrees Fahrenheit, the unit’s air filter may be clogged, or the condenser coils may require cleaning.
  • A clogged air filter can cause the evaporator coils to frost over and the unit’s efficiency to be greatly reduced. This is why you should clean the air filter regularly or, if necessary, replace it with a new one.
  • Over time, the condenser coils collect dust and debris, so it is recommended you clean the coils periodically by using compressed air to dislodge the debris along with a vacuum cleaner extension to clean the inside of the cabinet.

Repair Clinic has the parts to fix your air conditioner

Need a new fan motor, blower wheel, air filter, or control board for your window or wall air conditioner? RepairClinic.com makes it simple to locate the exact part that fits your unit with its full inventory of original manufacturer replacement parts from brands like Admiral, Bryant, Carrier, Frigidaire, GE, Goldstar, Goodman, LG, Lennox, Payne, Rheem, and WeatherKing. Just enter the full model number of the air conditioner in the Repair Clinic website search bar to see a complete list of compatible parts. You can then use the “Part Category” filter (Example: “Blower Wheel & Fan Blade”) and “Part Title” filter (Example: “Blower Housing”) to narrow that list down to identify the specific replacement part you’re looking for, whether you’re searching for a new capacitor, power cord, or vertical fin for the unit’s directional air vent.

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