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INFORMATION SERIES: Air Conditioning

Most central air conditioning systems are of the electric compressor type. This is the system addressed in this Information Series. Other types include the gas absorption system, the chilled water system and the evaporative cooling system. There are two basic styles of electric air conditioning systems: (1) the single (unitary) package type with entire system installed within the house and (2) the split system (illustrated) which has the condenser/compressor outside the house. The basic physics principle involved in modern air conditioning is that a gas expanding under pressure absorbs heat while a gas condensing to a liquid releases heat. The major elements of an air conditioning system are an evaporator coil and fan, a condenser coil and fan, a circulation refrigerant and a compressor, as illustrated.	It can be said that an air conditioning unit or system operates by removing heat from the air inside and releasing it outdoors. Heat pumps. which both cool and heat, operate in much the same manner but are reversible for winter use. When adding central air to an existing house, be certain that you have the proper size fan. ductwork and returns since cold air, being heavier than hot air, dictates system adjustment for efficient operation. Central air conditioning systems do not require a burdensome amount of maintenance, but some simple care must be done periodically if the unit's maximum economic life span is to be achieved. A regular maintenance program can add up to 50° in extra years of use. Normally, a central system can be expected to last 5 to 8 years. The first element to require replacement is usually the compressor. Unfortunately. it is also the most expensive component of the system. Replacement compressors have a shorter lifespan usually because of system contamination when shipping and installing. Aside from the sound recommendation of having an annual service check of the system (and the refrigerant level) by a local cooling contractor, the following are the most important considerations for the homeowner: Reset dampers for air conditioning at the start of the cooling system. A damper adjustment is required only if there are not separate ducts for the cool air and if the return has both a ceiling and floor register. See that all inlets and outlets. both indoors and out, are free from obstruction and dust. Clean and/or replace air filters monthly in season. Service the electronic air cleaner if you have one. If there is a drain pan under the unit. as is the case in many attic installations, be sure the pan is clean and the condensate drain open. If your unit has a condensate pump, keep it clean and in working order. Add a lock to the outside electric disconnect box to keep out the prying hands of children. Find a comfortable setting above 78VF/25`C and don't change it. Consider a set-back thermostat. Insulate all ducts that pass through hot areas like attics, garages and crawl spaces. Minimize hot air infiltration by weather stripping windows and open doors. The HouseMaster Technical Staff advises to never operate an air conditioning system when the outside temperature is below 60'F for most of the time. This can damage the compressor. When preparing for the summer season, turn the power on to the system at least one day in advance to energize the compressor crankcase heater. Run the fan only when the cooling thermostat is set on high.

The refrigerant liquid passes through an expansion device into the evaporator coil and expands to a gas. In the process, it absorbs heat from the air forced over and through the evaporator coil. The cooled air is blown from the coil into an air collection chamber (plenum) from which it is distributed through ducts into the space to be cooled. The gaseous refrigerant circulates from the evaporator coil the the compressor where it is compressed back under pressure into a high pressure gas. The gas then passes into the condenser coil where it usually transfers heat to the outdoors and becomes a liquid. A condenser fan forces air across the condenser coil where it picks up heat. Some condensers use water to cool the refrigerant rather than air.

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ENCO Home Inspection, LLC is a wholly, independently owned and operated franchisee of HMA Franchise Systems, Inc. The information and views provided within these web pages have no reflection on HMA, and HMA is held harmless from any statements, views, comments or otherwise.

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