Air Conditioning Compressor Condenser Unit Inspection Checklist for Owners & Inspectors
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A quick visual inspection checklist for the outdoor air conditioning system compressor/condenser unit
How to inspect the outdoor components of an air conditioning system - simple tips for home owners and home inspectors
Questions & answers about how to inspect the outdoor compressor/condenser unit for signs of trouble

Air Conditioner Inspection Checklist: This air conditioning inspection article discusses the how to perform a simple visual inspection of an air conditioning compressor-condenser unit, including links to more detailed air conditioning inspection,diagnosis and repair articles useful in the evaluation of air conditioner compressor noises, hard starting, lost cooling capacity, and detection of a burned out compressor or A/C compressors at or near end of their life.

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Maintenance tips including attention to compressor support pads and avoiding air conditioning refrigerant leaks are addressed. Initial, simple diagnostic checks of the air conditioning compressor are also described at Compressor failure diagnosis.

AIR CONDITIONING & HEAT PUMP SYSTEMS describes the major components of an air conditioning system. Sketches and photographs are provided, and common defects for each A/C component are listed along with visual or other clues that may suggest a problem or probable failure of each components. We explain how an air conditioning service technician will diagnose certain common air conditioning system failures or defects. We include photographs to assist readers in recognizing cooling system defects.

If your air conditioning or heat pump system has lost its cooling capacity or won't start see REPAIR GUIDE for AIR CONDITIONERS. See How to determine the cooling capacity of air conditioning equipment if the system seems to be working but is inadequate to cool your building. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

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How do We Inspect an Air Conditioning Compressor - Visual Inspection Procedure

The (usually) outdoor half of a typical air conditioning system is a unit containing the refrigerant compressor and condensing coil. The air conditioning compressor motor is a pump which draws heat laden refrigerant gas from the building's indoor components (evaporator coil and air handler), and compresses the low pressure refrigerant gas to high pressure and higher temperature.

The diagnosis and repair of various defects in the air conditioning compressor/condenser unit are discussed in detail using the links provided at the left of this page.

Here is a little visual inspection checklist that any homeowner or home inspector can perform.

Sketch courtesy of Carson Dunlop.

Air Conditioner Compressor Unit Inspection Checklist for an Air Conditioner Report - Outdoor Unit Observations

Location of the Compressor/Condenser: Locate the outdoor unit or units and look at the characteristics of just where the unit(s) have been placed:
- Is there good air circulation around the compressor/condenser unit or is it too close to a wall, to close to an overhead deck, porch, shrubs - Details are at INSTALLATION ERRORS, COMPRESSORS
- Is the unit too close to the property line - a possible noise issue for neighbors or a local building code violation? Most municipalities require that the compressor be at least 10' from the property line.
- Is the compressor/condenser too close to a gas appliance vent or to a clothes dryer vent? - Details are at INSTALLATION ERRORS, COMPRESSORS
- Are all of the cabinet parts and cabinet base above ground - the unit should not be partially buried
Condition of the compressor/condenser cabinet: look for rust damage or dents from having been struck by a garden tractor or dropped during installation
Levelness of the condenser/compressor unit: the unit should be level or within 10 deg. of level. See CONDENSING COIL REPAIR REPLACE
Condition of the compressor/condenser condensing coil: look for evidence of damage to the cooling fins or dirt, debris, grass clippings blocking the air flow of the unit. See CONDENSING COIL REPAIR REPLACE
Condition of the compressor/condenser fan: look for evidence of damage to the fan itself (rare). See FAN, COMPRESSOR/CONDENSER UNIT for details.
Presence of an electrical service disconnect switch at the air conditioner compressor/condenser: a service disconnect switch, fuse, or circuit breaker should be installed, usually on the building wall close to the unit. Check the size of the fuse or circuit breakers and compare with the overcurrent protection specified on the data plate on the compressor/condenser unit body. See A/C - HEAT PUMP CONTROLS & SWITCHES.
Condition of the wiring to the air conditioner compressor/condenser unit: look for signs of damage or overheating, broken conduit that should be protecting the wiring. A home inspector or electrical inspector will compare the size (current carrying capacity) of the wiring with the fuse or circuit breaker size and the size specified by the data tag. She should also check that the wiring to the compressor/condenser is rated for outdoor use or is suitably installed in conduit. See ELECTRICAL INSPECTION, DIAGNOSIS, REPAIR.
Condition of the air conditioner refrigerant lines: look for lost insulation on the suction line; look for absence of any bend or slack in the refrigerant line; if the compressor/condenser is connected to copper piping that is rigid between the unit and the building wall, vibration, settlement, slight movement can produce a refrigerant leak. See REFRIGERANT LEAK DETECTION.
Air Conditioner Data Plate Information: is there a data plate at all? If you can find it, record the model, serial number, and other data from this tag - it can help locate service manuals, system specifications such as RLA, maximum fuse size, and it will permit you to find the age and cooling capacity of the unit. See DATA TAGS on AIR CONDITIONERS. A home inspector can be asked to make a rough comparison between the cooling capacity of the compressor and the square footage of the building it serves. See COOLING CAPACITY, RATED for how to do this, and see AIR CONDITIONER BTU CHART.
If the compressor can be run, listen to the motor and fan motor when the unit starts and after it gets running; Noisy or hard starting compressors may be at or near the end of life or may need service and repair. See NOISES, COMPRESSOR CONDENSER, and see OPERATING DEFECTS.
Operating temperatures: a home inspector or service technician may use other instruments, including measuring simple air temperatures at the compressor/condenser to get an idea how well the system is functioning. See OPERATING TEMPERATURES.

Air Conditioning System Diagnostic Articles

At LOST COOLING CAPACITY, our focus is on the case in which the air conditioning system seems to be "running" but not enough cool air, or no cool air at all is being delivered to the occupied space. Sketch from Carson Dunlop.
At OPERATING DEFECTS we take you through the major air conditioning problem symptoms and how to get the air conditioning system working again.
At A/C - HEAT PUMP CONTROLS & SWITCHES we explain the many electrical switches and controls that control an air conditioner or heat pump system. You'll need to check these if your air conditioner won't start.

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Questions & answers about how to inspect the outdoor compressor/condenser unit for signs of trouble

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INSPECTION CHECKLIST - OUTDOOR UNIT

Thanks to Mark Cramer, Tampa Florida, for assistance in technical review of the "Critical Defects" section and for the photograph of the deteriorating gray Owens Corning flex duct in a hot attic. Mr. Cramer is a Florida home inspector and home inspection educator.
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).
Thanks to Scott at SJM Inspect for suggesting this EPA document and for technical editing remarks regarding our air conditioning website, SJM Inspection Service LLC, serves the entire state of CT, sjminspect.com 203-543-0447 or 203-877-4774 5/16/07

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Complete List of Air Conditioning & Heat Pump Design, Inspection, Repair Books at the InspectAPedia Bookstore.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ^® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.

Modern Refrigeration and Air Conditioning, A. D. Althouse, C.H. Turnquist, A. Bracciano, Goodheart-Willcox Co., 1982
Principles of Refrigeration, R. Warren Marsh, C. Thomas Olivo, Delmar Publishers, 1979
"Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
Refrigeration and Air Conditioning Technology, 5th Ed., William C. Whitman, William M. Johnson, John Tomczyk, Cengage Learning, 2005, ISBN 1401837654, 9781401837655 1324 pages
Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).
Air Conditioning Inspection, Diagnosis, Repair, Efficiency all the basics for home owners, inspectors, new repairmen
Air Conditioning SEER - New DOE Air Conditioner and Heat Pump Efficiency Standard
Asbestos HVAC Ducts and Flues field identification photos and guide
Fiberglass: Indoor Air Quality Investigations: Fiberglass in Indoor Air, HVAC ducts, and Building Insulation

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How do We Inspect an Air Conditioning Compressor - Visual Inspection Procedure

Air Conditioner Compressor Unit Inspection Checklist for an Air Conditioner Report - Outdoor Unit Observations

Air Conditioning System Diagnostic Articles

Questions & Answers regarding this article

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Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair