Central air conditioning is a type of split system. The condenser and heat exchange is located outside the house. Cold refrigerant is passed through tubing into the building where it is used to cool the interior. The inside unit uses the same blower and ductwork as the furnace to pass cool air throughout the structure.
Because it is married to the existing furnace and ductwork, efficiencies of a central air conditioning system depend partly on the equipment already installed. An older furnace blower motor or improper ductwork will increase operating costs.2 This “marriage” saves money on installation because ducts and the blower are dual purpose – used for both heating and cooling. On the other hand, problems with duct work will adversely affect air conditioning efficiency and installers should make a duct inspection one of their primary jobs.
Choosing a brand
From an installer’s point of view, there is no one best brand of central air conditioning. This is because they think of systems as assembled parts rather than single units.3 For instance, if Copeland makes the best scroll compressor on the market, it doesn’t matter if you buy a Trane, American Standard or Friedrich brand name, that compressor has to be under the hood. The same is true for other critical parts like the thermostatic expansion valve.
The best recommendation is to start, not with a particular brand, but the best installer you can find. This is the contractor who will install, service and who will do the warranty work on your unit. They will have one or more brands they prefer and this will vary in different parts of the country. One good way to get leads is to look around your area and see what’s already installed. You can often see the HVAC company information right on existing units.
Finding a reputable installation company first allows you to have them come out and assess your needs. This is the time to discuss prices and brands. Your follow up should include talking to previous customers about similar systems – their experiences and how satisfied they are now.
You can also tell quite a bit about a brand by the warranty they offer. The best units will offer ten years (or more) on parts, compressor, and coils. Note that these warranties may require a licensed installer or even a company affiliated installer to be valid.
Finally, because the air conditioning market is in continuous flux with mergers, acquisitions and foreign company entry into the US market, take the time to research the manufacturer you have decided upon. You don’t want to be caught short a few years from now when your product is obsolete, the company defunct and no parts readily available. Information by brand can be found online.3
Common problems with central air conditioning
Other than not hiring a quality installer, most problems arise because of improper maintenance or unrealistic expectations. Any existing flaws in the heating system will need repair for the central air to function properly – this should be part of the installation estimate from your contractor.
Air distribution can be an issue with warm and cold spots only appearing after the system has been in use for some time. This is partially dependent on outside weather conditions, but may also be due to variations in air flow in the house. One danger is mold growth when water accumulates because of condensation in an area that is overcooled – commonly, this happens in ducts that are not level. Dripping water that gets into drywall is a prime source for mold growth. Reducing the humidity in the house with a dehumidifier will help as will inspecting and repairing any problem ductwork.
Because so much depends on hiring the right contractor, to prevent problems, a checklist should be used. The Air Conditioning Contractors of America (ACCA.org) publishes a questionnaire you can use to evaluate a contractor before you hire them. It can be downloaded from their website.4
Maintenance is a critical part of owning a central air conditioning system. Too many homeowners experience problems because they have ignored their system until a sudden demand causes a failure. These failures are most likely to happen when the system is needed most because that is when it is under the most mechanical stress. This is also when HVAC companies are the busiest – they may not be able to rescue you without a significant delay.
Not every problem will require the services of a technician and you should be familiar with the coils, fan, and the normal operating sounds of your unit. As part of the installation, you should be provided with a manual from the manufacturer for your unit. If you do not have one, they can be downloaded from the Internet from the manufacturer’s website.
Because calling a technician out when there isn’t a need is expensive and frustrating, see what you can determine yourself before requesting help. There are troubleshooting guides online to help, both general and specific for a particular product.5 However, never attempt a repair that involves replacing parts (except the filter) yourself. If you damage the unit, you will likely void your warranty and may even hurt yourself. You should know how to shut the power off to your unit and know what to do in case of a refrigerant leak. (DIY or hire an AC pro story here. –Dave)
A central air conditioning system represents a significant investment in your home. If you keep it maintained and serviced, you can expect 15 or more years of use and if you do sell your house, it will increase the value.