Air Conditioners: Commonly Asked Questions

Air Conditioners- Commonly Asked Question

Is Air Conditioner (A/C) bad for you?

Air conditioning is not bad for you. It is actually good for you in most cases. According to the Center for Disease Control and Prevention (CDC), air conditioning is one of the most important defense you have against certain disease such as Legionnaires disease (Legionnnaires disease is caused by bacteria called Legionella that might be present in the water in air conditioning units for large buildings.

What is a BTU?

BTU is an ancronym for British Thermal Unit. In simpler terms, it is the unit of measurement used to measure the “strength” of an air conditioning unit. Scientifically speaking, it is the amount of energy (heat) required to raise the temperature of one pound of water by one degree Fahrenheit ( 1°F ) at sea level.

How do I choose an Air Conditioner?

The power of an air conditioner is measured in terms of BTU (British Thermal Unit). To determine the appropriate “strength” air conditioner that meets your cooling needs, first you need to calculate the square footage of the room you want to cool. You can get this simply by multiplying the length of the room by its width. Once you have the square footage, find the corresponding A/C unit that is rated to cover your room. For example, window air conditioners with 7,000-8,000 BTUs can cover small rooms up to 250 sq. ft.

What is Central Air Conditioning?

Central A/C is a modern home cooling system where air is cooled at a central location. The cold air is then distributed to various parts (rooms) of the building by fans via ductwork. The key component of the central air conditioning sytem is the “compressor”. Air is cooled by compression of the refrigerant gas which in turn removes the “heat” from the house.

What are the types of central air conditioning?

Central air conditioning systems can be divided into two main types: A split system or packaged unit.

In a split system, a metal cabinet is located outside of the building which houses the condenser and the compressor. Another cabinet, located inside the building, houses the evaporator. In most of the split systems, the indoor cabinet also contains a furnace or an air handler.

In a packaged unit, the condenser, the compressor and the evaporator are all housed in a single cabinet located outside of the building.

Is it cheaper to run a window air conditioner or central air (Central Air vs. Window A/C)?

The answer depends on the type of area/room/building you are trying to cool. Even though window units appear cheaper in the short run, if you need more than a few of the window units, you are better off going with the central air. Besides the one time installation cost, the central air will actually end up saving you money in the long run. Moreover, central air cools more efficiently than a number of window units distributed throughout the building.

However, if you have a very small area, or a room or two, you are obviously better off with window units.

How does a portable air conditioner work?

A portable air conditioner takes the outside air in through a hose and uses that air to cool the unit. It then uses the second hose to expel the hot exhaust air outside. Portable air conditioners that make use of these two hoses to suck outside air in and expel hot air out are called “dual hose”. Since the flow of air occurs both ways, in and out, there is no ‘negative air pressure‘ in the room being cooled off.

The “single hose” portable air conditioner, on the other hand, pulls air from the room and expels the warm air and moisture outside through the use of a single hose. Since, air is constantly being taken out of the room, it creates a small “negative air pressure” and warm air can seep in from cracks and gaps to balance the pressure. Single hose air conditioners are therefore meant only to be a temporary solution and are less efficient than their dual hose counterparts.

What is the best portable air conditioner?

There are a variety of excellent portable air conditioners out in the market. Basically, what you are looking for is an unit that has enough BTU to cool the room/area, is easy to move around, and easy to store during winter months when you don’t need to cool things off. We have a handy guide that has a fairly detailed review of the top portable air conditioners. You cannot go wrong with any one on the list.  Whynter ARC-14SH has pretty good reviews.

Do window units pull air from outside?

Window air conditioning units work by venting (pulling and removing) the hot air from inside the room and blowing the cooled air from outside into the room. However, you should note that when the A/C is in ‘Fan Only’ setting, it simply blows the outside air in (just like a simple fan).

What is the best window air conditioner?

Air conditioners have become smarter, more efficient and cheaper. Here is a good guide to the ten best window air conditioners in the market. Frigidaire makes a pretty good one – Frigidaire 10000 is smart, efficient and sleek.

Why is my AC running constantly?

There are a few reasons why your AC might be running constantly:

  • One of the most common reasons is the accumulation of dirt on your AC’s filter. When the filter is clogged by dust and dirt, the flow of air is severely restricted. Since the AC does not get enough air flowing over its condenser coils, it is unable to remove the humidity fast enough and cool the air to the temperature you want. It therefore, keeps running when it shouldn’t. Therefore, it is a good idea to clean your air conditioner’s filter on a regular basis to make it run more efficiently.
  • Sometimes your thermostat or your target temperature gets set so low that the AC can never get the rooms cold enough to reach the set temperature. To meet that constant demand for cool air, it keeps running continuously. Try testing the unit by setting the temperature above room temperature and see if stops. If you have a reasonable goal temperature set but the AC can never make the room cool, it could also be that the unit is not “powerful” enough for the given square footage of the area it is try to cool off. Try using a unit with higher BTU.
  • Sometimes, the air conditioning units have a “Fan Limit Switch” by the air blower. If it is manually set to run, it could run continuously independent of the thermostat setting. You could try to switch it from “manual” to “auto” so that the fan only runs when the thermostat kicks it on.
  • The evaporator coil can get frozen from excessive usage. This will not only cause the AC unit to run continuously but it will also blow warm air. If this is the case you can try “thawing” out the unit by turning it off completely for a few hours. If it does’nt work, you will have to seek professional help.

Patrick Cooper

Patrick has over a decade’s experience writing about consumer electronics on the web. An avid traveller, he is the father of two adopted pitbulls and a greyhound. Cheif editor at, right now Patrick lives in Austin, TX. Reach him at