Photograph of  this unusual attic air conditioning system is an example of
the range of human creativity observed during a career of building inspections Checklist of Critical Defects in Air Conditioning or Heat Pump Systems

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Air conditioner defect checklist: here we list the types of critical problems that may occur in air conditioning or heat pump systems, a first step in understanding how an air conditioning service technician will diagnose certain common air conditioning system failures or defects. This air conditioning/heat pump inspection guide lists critical air conditioning system defects which a building inspector or owner should not miss. We include photographs to assist readers in recognizing cooling system defects. This HVAC article series describes the inspection, diagnosis & repair of residential air conditioning systems (A/C systems) & heat pump systems to diagnose problems as well as to inform home buyers, owners, and home inspectors of common cooling system defects.

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Critical Defects in Air Conditioning Equipment Inspections

Beginning at AIR CONDITIONING & HEAT PUMP SYSTEMS the major components of an air conditioning system are described, sketches and photographs are provided, and common defects for each cooling system component are listed along with visual or other clues that may suggest a problem or probable failure of A/C components.

Example home inspection report language used to report air conditioning system defects and cooling system repairs needed is provided to describe common air conditioning system defects. We continue to add to and update this text as new details are provided. Contact us to suggest text corrections or additions and, if you wish, to receive online listing and credit for that contribution.

Critical defects which an inspector should not fail to detect when examining any building component or system are defects which form an immediate, significant safety hazard or defects which are quite likely to involve significant repair or replacement cost, and which involve components or systems which are necessary to occupy and use the building. Methods for detection and diagnosis of these defects are discussed in this document and in its references. Suggestions for inclusion or exclusion of items in this list are invited - see the link "Contact Us".

  • Function: Air conditioning compressor needs replacement. See COMPRESSOR & CONDENSING COIL and see LOST COOLING CAPACITY
  • Function: Cooling is delivered to only part of the building, e.g. only to one floor. See DUCT SYSTEM DEFECTS
  • Air Duct System Safety: Unsafe return air intake which may draw in carbon monoxide at heating equipment. See DUCT SYSTEM DEFECTS. Note that more indirect building defects and hazards, such as a toxic airborne mold reservoir or toxic gases or chemicals (such as sewer gas) may be picked up and distributed through a building from one area to another by duct system defects.
  • Uneven air supply resulting in uneven temperatures especially on the first floor of a two story house with ductwork between the first and second floor. See DUCT SYSTEM DEFECTS
  • Inadequate cooling capacity for building. See LOST COOLING CAPACITY
  • Low temperature split (indicating inadequate cooling due to refrigerant leak). See A/C REFRIGERANTS and see COOLING COIL or EVAPORATOR COIL
  • Refrigerant leaks at condenser or evaporator coils (usually requires replacement of coil.) See A/C REFRIGERANTS
  • Dirty air handler. (Major expense to clean properly.) See AIR HANDLER / BLOWER UNITS and see AIR FILTERS for HVAC SYSTEMS
  • Leaking return ducts in crawl space. See DUCT SYSTEM DEFECTS
  • Air Conditioning System Safety: Unsafe electrical wiring: aluminum branch circuits and FPE Stab-Lok or Zinsco circuit breakers may have been used to power the compressor. Look for evidence of overheating or over fusing at the service cutoff and in the electrical panel and at the service cutoff by the compressor/condenser [This item is not agreed-on as a critical defect by all reviewers] For details see:
    • ALUMINUM WIRING HAZARDS - aluminum electrical wiring often burns-up at high-amperage electrical connections such as air conditioner wiring.
    • Federal Pacific Electric (FPE) FPE Stab-Lok Circuit Breakers can increase the risk of a fire if these breakers are used on air conditioning or heat pump equipment
    • Zinsco Electrical Circuit Breakerss: overheating, failure to trip, burn-ups involving Zinsco and certain Sylvania electrical panel components. These components can also increase the risk of a fire if these breakers are used on air conditioning or heat pump equipment

Air Conditioning System Operation Report Language

Observation of the condition of an air conditioning or heat pump system, typical inspection report language includes these succinct descriptions of findings:
... The cooling system operated normally at the time of our inspection.
... Caution: The equipment was not run and therefore not tested
... because
... outside temperature was estimated to be at or below 50 degF.
... the system has been "shut down" for some time.
... In cold weather operation could damage the compressor, particularly if it has been left "shut down".
... Individual components were not operated - see note below.
... Any deficiencies noted were based only on visual inspection. We did no
... electrical, gauge or pressure tests on this equipment.

Operating Note: Many such air conditioning systems must be left with power turned on (we found switches in the "off" position) for 24 hours prior to running the equipment. This permits heaters at the compressors to assure good oil flow in those components. To operate the equipment without this step risks very costly damage to the compressor. When a system is not operated we can make no representation that it functions correctly and adequately.

... We recommend that you ask the owner about the condition of this equipment.

... If weather permits, it should be checked by an HVAC service person and returned to operating status prior closing sale

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