Central Air

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A Guide to Understanding Central Air

Particularly in homes across the United States, central air conditioning has become the norm, not the exception. Because family sizes are constantly growing, as is the occupant-to-home ratio, it becomes more and more necessary to cool down an entire house. For this reason, central air offers several benefits.

How Central Air Worksair

A central air conditioner works similarly to your refrigerator. However, instead of spilling the heat behind the unit, like a refrigerator does, the air conditioner will funnel the expelled heat outside to the compressor, which is located outside your home. In essence, the unit will consume hot air from the interior of your house and release it outside, effectively cooling the temperature of your home.

Central air uses ducts to distribute cool air to more than one room. Some use pipes to distribute cold water to heat exchangers and do not plug into a standard electrical outlet. The power necessary to run a central air conditioner depends entirely on the size of your home and the unit itself. Before installing a device, always have a professional audit your home to estimate the size unit you'll need.

Types of Central Air

  • Split system: In split-system central air conditioners, an outdoor metal cabinet contains the condenser and compressor, while an indoor cabinet contains the evaporator. In many, the indoor cabinet also contains a furnace. The evaporator coil is installed in the cabinet or main supply duct of the furnace. Split systems are most common economical for homes that already have a furnace but no air conditioner.
  • Package system: Unlike the two-piece split system, a package system air conditioner has the evaporator, condenser and compressor all located in one cabinet, usually on a roof or a building-adjacent slab of concrete. Usually involving electric heating coils or a natural gas furnace, package systems eliminate the need for an indoor furnace.

Important Central Air Features

  • BTU, or British thermal units, are used as a rating system on the power of an air conditioner. Some manufacturers will measure this in tons, which are each equal to 12,000 BTU. Typically, the size of the compressor is indicative of BTU. You always want a BTU level that matches your home size, never more, never less. An undersized unit will not have the cooling capacity to efficiently cool your house down, requiring you to run it longer and harder than a properly sized unit. Oversized units will have a larger compressor than necessary, consuming more energy than a properly sized unit and costing the owner more money.
  • SEER, or seasonal energy efficiency rating, refers to how many BTU of heat your unit removes for each watt of electricity it consumes. The higher the SEER, the less it will cost to operate your unit. Federal Law requires a minimum SEER number of 13, and the higher the SEER, the more the unit will cost, but the money you will save over the life of your unit is much more. For this reason, you should only install central air to a home you intent to keep for a while, otherwise you will waste money.

Central Air Benefits

Central air conditioning systems have several benefits when compared to smaller units. While they are a larger investment, central air systems can often save homeowners money in the long run, particularly for users who would otherwise need several room units.

Also, when an air handling unit turns on, the room air is drawn in from various parts of the building through return-air ducts. This air goes through a filter system, where particles such as dust and lint are removed. More advanced filers can also remove some pollutants. This filtered air is then rerouted to other rooms, repeating the cycle and actually cleaning your air.

Finally, because the condenser unit on a central air system is located outside the building, it makes less indoor noise than free-standing or wall unit air conditioners.

Central Air Cost

Because central air conditioning is a very costly investment, you should weigh your options carefully. If you plan on changing addresses soon or completely remodeling, you will likely want to wait and install central air later. You'll lose money on a central A/C unit in the short run, but you'll save money in the long run.

To add central air to an existing forced-air heating system, the average home installation will cost between $3,500 and $4,000. This takes two or three days and involves little or no change to the existing ducts. If any ducts need altering or adding, then the work required will be greater, and the price will double. For smaller houses, between 800 and 1,000 square feet and no existing duct work, the installation can cost between $2,000 and $6,000. Higher-end systems can still end up costing as much as $10,000.

Last Updated: January 18, 2012
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