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Drawing of key parts to a modern air conditioning compressor/condensor unitAir Conditioner / Heat Pump Inspect & Repair

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How to Buy, Diagnose, Repair Air Conditioners & Heat Pumps:

This air conditioner & heat pump inspection, installation, diagnosis & repair article series explains in detail the inspection, troubleshooting diagnosis, and repair of all types of residential and light commercial central air conditioning and heat pump systems.

Page top image & air conditioning schematic drawing below were provided courtesy Carson Dunlop Associates.
Serbian flag SRPSKI PREVOD nad današji stranica [Serbian translation of air conditioning diagnosis and repair articles]



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What are the Parts of an Air Conditioning or Heat Pump System & How do Air Conditioners & Heat Pumps Work?

Frost blocked cooling coil (C) Daniel FriedmanThe purchase, installation, inspection, diagnosis, & repair of residential and commercial air conditioning (A/C) & heat pump systems are described in this InspectApedia.com article series.

To find what you need quickly, if you don't want to scroll through this index you are welcome to use the page top or bottom SEARCH BOX to search InspectApedia for specific articles and information.

Photo: a frost-blocked cooling coil in the air handler of an air condtioning system will stop the delivery of cool air to the building. [Click to enlarge any image]

If your air conditioner or heat pump system is not working, start at LOST COOLING CAPACITY for help in diagnosing and repairing the trouble.

Let's introduce the most basic concepts of air conditioning first:

Just below is a simple explanation of how an air conditioning system works, with enough detail so that it isn't simply magic (the schematic of an air conditioner shown at page top is compliments of Carson Dunlop Associates - a Toronto home inspection, report writing system & education company.

How an Air Conditioner or Heat Pump Works

A detailed list and photos of air conditioner components can be seen at AIR CONDITIONER COMPONENT PARTS.

  1. A air conditioning or heat pump compressor which compresses low pressure refrigerant gas into a high pressure, high temperature gas. Usually the compressor is in the outdoor portion of an air conditioning or heat pump system.

    The air conditioner or heat pump compressor unit is basically a high pressure pump driven by an electric motor. The air conditioning compressor is usually packaged in the outdoor compressor/condenser unit illustrated by our page top drawing. You won't see the actual motor - it is inside the compressor/condenser unit shown in the photo below.

    See COMPRESSOR CONDENSER, and see REFRIGERANT GASES & PIPING

  2. Photograph of a modern A/C system compressor condenser unit pairA condenser or condensing unit: typically a condensing coil inside which high temperature high pressure refrigerant gas flows, and over which a fan blows air to cool the refrigerant gas back to a liquid state (thus transferring heat from the refrigerant gas to the air being blown by the fan).

    The condenser unit is basically a coil of finned tubing and a fan to blow air across the coil. Usually the condenser unit is in the outdoor portion of an air conditioning system, often packaged along with the compressor motor discussed above.

    See COMPRESSOR CONDENSER and see our page top sketch too. The change of state of the refrigerant, from hot high pressure gas to a liquid releases heat, including heat collected inside the building) to the outdoors.

  3. A metering device which dispenses liquid refrigerant into an evaporator coil. The metering device may be simply a thin section of tubing (a capillary or "cap" tube) or it may be a bit more sophisticated thermostatic expansion valve (TEV) which includes a temperature sensing control that can open and shut the device against refrigerant flow.

    See THERMOSTATIC EXPANSION VALVES or see CAPILLARY TUBES.

  4. An evaporator coil or cooling coil: typically the cooling coil is a section of finned tubing (it looks a lot like a car radiator) into which liquid refrigerant is metered and permitted to evaporate from liquid to gas state inside the coil.

    This state change of the refrigerant, from liquid to gas, absorbs heat, cooling the evaporator coil surface and thus cooling indoor air blown across the cooling coil. Usually the cooling coil is located inside the air handler.

    See AIR HANDLER / BLOWER UNITS and articles like DIRTY COOLING COIL / EVAPORATOR COIL.

    Evaporative cooling systems, or swamp coolers are discussed separately at EVAPORATIVE COOLING SYSTEMS.

  5. Photograph of a modern A/C system indoor air handler unitAn air handler and blower unit which provides a fan to blow building air across or through the evaporator coil.

    The air handler blower fan unit moves building air across the evaporator coil surface in order to condition building air by cooling it (and thus also by removing moisture from the cooled air).

    See AIR HANDLER / BLOWER UNITS and BLOWER FAN OPERATION & TESTING.

  6. A duct system which distributes conditioned air from the air handler in to the occupied space (supply ducts), and which takes air from the occupied space and returns it to the cooling system air handler.

    See DUCT SYSTEM

  7. Photograph of a modern A/C system compressor split system inside air handlerHeat Pump Systems use the same components we have described just above, with the addition of a reversing valve that in essence permits the system to run "backwards" in cold weather.

    Split system air conditioners and heat pumps (indoor unit shown in our photo) dispense with a duct system. The wall unit combines a heating or cooling coil and a blower fan to move conditioned air into the room.

    In air conditioning mode the heat pump is moving heat from inside the building to outdoors while in heating mode the heat pump is moving heat from outdoor air (or water in some designs) to the building interior.

    Because the ability of a heat pump to extract heat from outdoor air diminishes at low outdoor temperatures, heat pump systems in northern climates also include a backup or auxiliary heating system.

    Details of how heat pumps work, are inspected, diagnosed, and repaired begin at HEAT PUMPS.

  8. Air conditioner controls and features, which include a room thermostat, electrical switches, fuses or circuit breakers, condensate handling system, and air filters.

    See OPERATING CONTROLS and AIR FILTERS for HVAC SYSTEMS

    Or see THERMOSTATS, HEATING / COOLING for the basics of how to turn the air conditioner on & set room temperature.

For more photographs of these various air conditioning and heat pump parts, and for an explanation of where these air conditioning components are physically located, see A/C COMPONENTS which discusses and helps you name and recognize various  Indoor A/C Components and Outdoor A/C Components

HVAC Service Technician Licensing

Photograph of wall convector air conditioner being servicedHeating, air-conditioning, and refrigeration mechanics and installers are required to be licensed by some States and localities. Requirements for licensure vary greatly, but all States or localities that require a license have a test that must be passed.

The contents of these tests vary by State or locality, with some requiring extensive knowledge of electrical codes and others focusing more on HVACR-specific knowledge. Completion of an apprenticeship program or 2 to 5 years of experience are also common requirements.

Our photo shows an HVAC repair technician disassembling and cleaning a wall-convector unit in a New York City apartment.

In addition, all technicians who purchase or work with refrigerants must be certified in their proper handling. To become certified to purchase and handle refrigerants, technicians must pass a written examination specific to the type of work in which they specialize.

The three possible areas of certification are:

Type I—servicing small appliances;

Type II—high-pressure refrigerants; and

Type III—low-pressure refrigerants. Exams are administered by organizations approved by the U.S. Environmental Protection Agency, such as trade schools, unions, contractor associations, or building groups.

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Continue reading at DIAGNOSTIC GUIDES A/C / HEAT PUMP or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES.

Or see AIR HANDLER / BLOWER UNITS - home

Or see AIR CONDITIONING & HEAT PUMP SYSTEM FAQs LIST- A/C & Heat Pump Diagnostic FAQs sorted by major topic area

Or see COMPRESSOR / CONDENSER REPAIR - home

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AIR CONDITIONING & HEAT PUMP SYSTEMS - HVAC inspection, installation, diagnosis & repair procedures provided free at InspectApedia.comor select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES.

INDEX to RELATED ARTICLES: ARTICLE INDEX to AIR CONDITIONING & HEAT PUMPS

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