Photograph of attic air conditioning air handler, condensate drips on floor Air Conditioning System Defects List & Home Inspection Education

  • DEFECTS LIST - AIR CONDITIONING - CONTENTS: Air conditioning system defects, definitions, and home inspection education topics. Lists of important air conditioning & heat pump defects for residential buildings. What does a home inspector need to know about air conditioning & heat pump systems? Home inspection training and education curriculum recommendations for A/C & heat pump courses
  • POST a QUESTION or READ FAQs about home & building inspection courses, standards, & defect checklists for air conditioning & heat pump inspections

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This article lists significant air conditioning system defects, definitions, and home inspection education topics.

This article series, beginning at BUILDING DEFECTS LISTS, provides lists of common building defects and basic defect knowledge that also outline recommended curriculum content for home inspector education.

The building defects and inspection points listed in these articles also guide homeowners and home buyers to building areas that merit careful attention and often point areas of safety concern or important maintenance and repair tasks.

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Home Inspection Education Curriculum - Air Conditioning


5.1   Air Conditioning Inspection Requirements

5.1.1 Knowledge Base

1.    Describe the function of central air conditioning systems.

2.    Describe the principle of central air conditioning including refrigerant cycle and heat transfer mechanisms. Describe an operating cycle, explaining the change in temperature, pressure and state of the refrigerant.

3.    List the materials and components of a central air conditioning system including the compressor, condenser coil, evaporator coil, condensate system, refrigerant lines, condenser fan, evaporator fan, duct system, thermostat.

4.    Describe the operation of an evaporative cooler comparing it to refrigerant based air conditioning systems. Describe an operating cycle.

5.    Describe the materials and components of a typical evaporative cooler including air handler, water reservoir, overflow, water makeup valve and float, pump, rotary drum, spray system, drip tube, air filter, cabinet, evaporative pad.

6.    Describe the features of  adequate installation and repair technique for refrigerant based air conditioning and evaporative coolers.

7.    Define the following terms with respect to air conditioning systems:

  • split system,
  • sensible heat,
  • latent heat of vaporization,
  • refrigerant,
  • compressor,
  • whole house fans,
  • vapor-compression refrigeration system (direct expansion, mechanical system),
  • capillary tube,
  • thermostatic expansion valve,
  • seasonal energy efficiency ratio(SEER),
  • one ton of cooling,
  • temperature drop,
  • crankcase  heater,
  • rated load amperage (RLA),
  • full load amperage (FLA),
  • receiver,
  • A coil,
  • condensate pump,
  • trap and condensate line,
  • filter/dryer,
  • sight glass,
  • expansion device (metering device),
  • condensate drain pan(tray),
  • auxiliary condensate drain pan(tray),
  • condensate trap,
  • condensate pump,
  • suction line (return line),
  • liquid line,
  • high pressure refrigerant side,
  • low pressure refrigerant side,
  • filter/dryer,
  • duct insulation,
  • swamp cooler,
  • rotary cooler,
  • spray cooler,
  • drip cooler,
  • bleed-off(evaporative cooler),
  • air gap(evaporative cooler),
  • attic fan, whole house fan.

8.    Outline the typical life expectancies of the air conditioning systems described above.

9.    Identify the codes or standards which apply to the air conditioning systems described above.

5.1.2 Inspection Skills

1.    Describe the inspection procedure for refrigerant based air conditioning and evaporative coolers.

2.    Identify the common defects listed on the next page.

3.    Describe the implication of each defect.

4.    Identify safety issues for the home inspector and occupant of the home (electric shock, injury due to moving parts).

5.    Communicate findings to client verbally and in writing, recommending corrective action where needed.


      CAPACITY                            REFRIGERANT LINES

      • Oversized                         • Damaged

      • Undersized                        • Leak

                                          • Lines too warm or too cold

      COMPRESSORS                         • Lines touching each other

                                          • Low points or improper slope in lines

      • Electric wires too small          • Missing insulation

      • Excess electric current draw

      • Excess noise or vibration               EXPANSION DEVICES - TE Valves

      • Inadequate cooling

      • Inoperative                             • Capillary tube crimped,

      disconnected, leaking

      • Missing electrical shutoff              • Thermostatic expansion valve loose, clogged, sticking

      • Out of level

      • Running continuously              CONDENSER FANS

      • Short cycling

      • Wrong fuse or breaker size        • Corrosion

                                          • Dirty

      AIR COOLED CONDENSER COILS          • Excess noise or vibration

                                          • Inoperative

      • Clothes dryer or water heater     • Mechanical damage

      exhaust too close

      • Corrosion                         • Obstructed airflow

      • Damaged

      • Dirty                                  EVAPORATOR FANS

      WATER COOLED CONDENSER COILS             • Corrosion

                                               • Damage

      • Cooled by pool water                   • Dirty

      • Leak                                   • Dirty or missing filter

      • No water                               • Excess noise or vibration

      • No backflow preventer                  • Inoperative

                                               • Misadjustment of belt or pulleys

      EVAPORATOR COILS                         • Undersized

      • Corrosion                               DUCT SYSTEMS

      • Damage

      • Dirty                                   • Dirty

      • Frost                                   • Disconnected or leaking

      • No access to coil                       • Humidifier damper missing

      • Temperature split too low               • Incomplete

      • Temperature split too high              • Obstructed or collapsed

      • Top of coil dry                         • Poor support

                                                • Poor balancing

      CONDENSATE SYSTEMS                        • Supply or return registers– obstructed

      • Dirt in pan                             • Supply or return registers – poor location

      • Inappropriate pan slope                 • Supply or return registers – too few

      • No float switch                         • Undersized

      • No auxiliary pan                        • Weak airflow

      • Pan not well secured

      • Pan cracked                             DUCT INSULATION

      • Pan leaking or overflowing

      • Rust or holes in pan                    • Incomplete

                                                • Missing


      • Damaged                           • Inoperative

      • Missing                           • Leaking

                                          • Poor wiring



      • Blocked or crimped

      • Disconnected, missing            • Damaged

      • Improper discharge point         • Dirty

      • Leaking, damaged, split          • Inoperative

      • No trap                          • Loose

                                         • Not level

                                         • Poor adjustment or calibration

                                         • Poor location


      • Cabinet or ducts not weathertight

      • Cabinet too close to grade

      • Clogged pads

      • Duct problems

      • Electrical problems

      • Excess noise or vibration

      • Leaking

      • Louvers obstructed

      • Missing or dirty air filter

      • No water

      • No air gap on water supply

      • Poor support for pump and water system

      • Pump or fan inoperative

      • Rust, mold and mildew


      • Excess noise or vibration

      • Inadequate attic venting

      • Inoperative


Watch out: these inspection lists do not list all possible defects for the systems discussed, and not all home or building inspectors will examine all of the items listed here.

These curriculae and building defect lists are based on smilar curriculum documents first prepared by Joe Scaduto, an ASHI member who prepared course material for Northeastern University's Building Inspection Certificate program in 1988, subsequently by DF, InspectApedia's editor, for New York University ca 1988 and later, with others, recommended to ASHI, the American Society of Home Inspectors.

ASHI did not adopt this material though currently that association as well as others offer extensive HOME INSPECTOR EDUCATION material.

The curriculum and lists of defects are informed by additional analysis of the process of home inspection that was developed beginning Calgary, AB for Canadian and U.S. home inspector education and certification examinations in 1997. Other early contributors to home inspection education in the U.S. and Canada include Dr. Jess Aronstein, Alan Carson, Mike Casey, Mark Cramer, John Cox, Dwight Barnett, Douglas Hansen, Rick Heyl, Larry Hoytt, Bill Merrill, Kevin O'Malley, Dennis Robitalille, Keith Peddie, Pat Porzio, Roger Robinson.



Continue reading at AIR CONDITIONING & HEAT PUMP SYSTEMS or select a topic from the More Reading links shown below.



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DEFECTS LIST - AIR CONDITIONING at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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