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AIR CONDITIONING & HEAT PUMP SYSTEMS

A/C - HEAT PUMP CONTROLS & SWITCHES
A/C DATA TAGS
A/C - HEAT PUMP CRITICAL DEFECTS
A/C DIAGNOSTIC FAQs
A/C REFRIGERANTS
A/C TYPES, ENERGY SOURCE
AGE of AIR CONDITIONERS & HEAT PUMPS

AIR CONDITIONER BTU CHART
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
  Basement Vertical Central Air Handlers
  Home Made Air Conditioning Systems
  Horizontal Attic or Crawl Space Air Handlers
  Portable Room Air Conditioners
  Rooftop-mounted Air Conditioners / Heat Pumps
  Split System or Ductless Air Conditioners
  Swamp Coolers & Water Cooled Air Conditioners
  Wall Convector Units, Heating / Air Conditioning
  Window / Wall-Mounted Room Air Conditioners
AIR CONDITIONER NOT WORKING

AIR FILTERS for HVAC SYSTEMS

AIR HANDLER / BLOWER UNITS
APPLIANCE EFFICIENCY RATINGS
BACKUP HEAT for HEAT PUMPS

BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING

BOOKSTORE - Air Conditioning "How To" Books

CAPACITORS for HARD STARTING MOTORS
CAPILLARY TUBES
CHINESE DRYWALL HAZARDS
CIRCUIT BREAKER SIZE for A/C or HEAT PUMP
CLEANING & Legionella BACTERIA
COMPRESSOR & CONDENSING COIL, A/C

CONDENSATE HANDLING, A/C
CONDENSATION or SWEATING PIPES, TANKS
COOL OFF HEAT Thermostat Switch
COOLING CAPACITY, RATED
COOLING COIL or EVAPORATOR COIL
COOLING LOAD REDUCTION by ROOF VENTS
COMBUSTION GASES & PARTICLE HAZARDS
CONDENSATE HANDLING, A/C
CONDENSATION or SWEATING PIPES, TANKS

DATA TAGS on AIR CONDITIONERS
DEFINITION of Heating & Cooling Terms

DEHUMIDIFICATION PROBLEMS
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE

DIAGNOSE & FIX AIR CONDITIONER / HEAT PUMP

DUCT SYSTEM & DUCT DEFECTS
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe
DUST CONTAMINATION FROM HVAC?

EDUCATION, HVAC SCHOOLS
ELECTRIC MOTOR DIAGNOSTIC GUIDE
ELECTRIC MOTOR OVERLOAD RESET SWITCH
ELECTRICAL POWER SWITCH FOR HEAT

ENERGY SAVINGS in buildings
EVAPORATIVE COOLING SYSTEMS
EVAPORATOR COIL or COOLING COIL
EXPANSION VALVES, REFRIGERANT

FAN, AIR HANDLER BLOWER UNIT
FAN AUTO ON Thermostat Switch
FAN, COMPRESSOR/CONDENSER UNIT
FAN CONVECTOR HEATERS - HYDRONIC COILS
FAN LIMIT SWITCH
FAN NOISES

FURNACES WARM AIR HEATING SYSTEMS

GASES, EXPOSURE, TESTING
  Carbon Dioxide - CO₂
  Carbon Monoxide - CO
  METHANE GAS SOURCES
GAS MEASUREMENT TOOLS
GAUGE, REFRIGERATION PRESSURE TEST

HEAT LOSS (or GAIN) in buildings
HEAT PUMPS

HUMIDITY LEVEL TARGET

INDOOR AIR QUALITY IMPROVEMENT GUIDE

INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS
LEED GREEN BUILDING CERTIFICATION

LOST COOLING CAPACITY

MANUALS & PARTS GUIDES - HVAC
MOTOR OVERLOAD RESET SWITCH

NOISY AIR CONDITIONER / HEAT PUMP
NOISE / SOUND DIAGNOSIS & CURE
  Air Leak Noises
  AIR CONDITIONING & HEAT PUMP NOISES

OPERATING COST
OPERATING DEFECTS
OPERATING TEMPERATURES

PORTABLE ROOM AIR CONDITIONERS
PRESSURE READINGS, REFRIGERANT

REPAIR GUIDE, AIR CONDITIONERS / HEAT PUMPS
REPAIR & DIAGNOSTIC FAQs for A/C

REFRIGERANTS
  GAUGE, REFRIGERATION PRESSURE TEST
  REFRIGERANT CHARGING PROCEDURE
  REFRIGERANT DRIERS & FILTERS
REFRIGERANT PIPING & DISTANCES
REFRIGERANT PRESSURE READINGS
SEER RATINGS & OTHER DEFINITIONS
SYSTEM OPERATION
SWAMP COOLERS

THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES

WATER COOLED AIR CONDITIONERS

More Information

Photos of Types of Air Conditioning Systems & A/C Energy Sources
InspectAPedia^® -

Air conditioning system energy source options
Types of air conditioning systems:
Photos & description of components of residential central air conditioning equipment
Photos & description of components of ductless and commercial air conditioning systems
Comparison of air cooled and water cooled air conditioning systems; evaporative coolers
Typical basement vertical air handler air conditioners & heat pumps
Typical attic or crawl space horizontal air handler systems
Independent split systems or ductless air conditioners & portable air conditioners
Wall Convectors, Window Air Conditioners
Home made or do-it-yourself air conditioners

Photographs of different types of air conditioning and cooling systems are provided here. We also illustrate the difference between air-cooled and water cooled air conditioners and evaporative coolers or "swamp coolers".

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This website answers most questions about inspecting, troubleshooting, and repairing central air conditioning systems.We describe how to inspect residential air conditioning systems (A/C systems) to inform home buyers, owners, and home inspectors of common cooling system defects.

We continue to add to and update this text as new details are provided. 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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A/C ENERGY SOURCES - Air Conditioning System Type by Energy Source

Air conditioning systems use these common energy sources to physically cool the condensing coils and thus the refrigerant

Schematic of a Typical Air-Cooled Air Conditioner or Heat Pump System

Air-cooled air conditioner systems: refers to the use of air to cool the compressor and the condenser coil used to return the refrigerant gas to a liquid state.

These split systems usually have an inside evaporator cooling coil installed to work along with the blower and duct system which might also be sitting atop a heating furnace. The outside half of the equipment contains the compressor and condenser coil.

Carson Dunlop's schematic shows how refrigerant moving through the system as a gas or liquid moves heat from inside the building (at the evaporator coil in an air handler) to outside the building (at the condenser unit's condensing coil).

The schematic of an air-cooled air conditioning system shown at left is compliments of Carson Dunlop

Water Cooled Air Conditioners vs Swamp Coolers - A Simple Comparison

Water cooled air conditioning systems: these work in a manner similar to the system listed above, but use water as a chiller to remove heat from the high temperature gas in the (usually but not always outside) compressor/condenser unit.

The schematic of a water cooled air conditioning system shown at left is compliments of Carson Dunlop

As with the air-cooled air conditioning system above, this schematic describes an air conditioner that uses refrigerant and coils to move heat from indoors to outside. But instead of moving heat from the condensing coil into air blown across the coil outdoors, we're moving heat into water circulated around a condensing coil.

Evaporative Coolers - Rooftop Units

Evaporative coolers, also called "swamp coolers" rely on the evaporation of water to cool building air, rather than the movement of a refrigerant through cooling coils.

Cooling towers, swamp coolers, and even a simple window fan blowing air across a pan of water and into a room are types of evaporative cooling systems.

Swamp coolers systems may use less energy than a refrigerant-gas and compressor type air conditioner but they'll only work where the ambient humidity is low enough to make it easy to evaporate water, such as in Arizona and other areas of the Southwest and Mexico.

We discuss evaporative coolers in more detail at EVAPORATIVE COOLING SYSTEMS.

Gas Chiller Air Conditioning Systems: these systems operate by the same principles as the above units, but they use heat to cause the refrigerant gas to change states rather than compression and expansion by a compressor motor. (Some refrigerators, including ones used in recreational vehicles also operate on this principle, as they can cool without requiring electricity to operate a compressor. Ammonia was the traditional gas used for this type of system.)

Photographs of Types of Air Conditioning Systems

Photos of Typical Residential Central Air Conditioning System

Photograph of the air handler unit or AHU for a typical up-flow residential air handler unit providing air conditioning

Photograph of a typical residential air conditioning compressor condenser unit, an older model, with a few visible defects and concerns

Photograph of Owens Corning flex duct - which deteriorates and fails in hot spaces

The most common central residential air conditioning system incorporates an indoor air handler unit or AHU which draws building air through return ducts from the living space, cools it by moving the air across an evaporator coil, and sends cooled and dehumidified air back into the living area through supply ducts and registers.

Liquid refrigerant is released into the interior of the evaporator coil, changing its state from liquid to gas and thereby cooling the evaporator coil (which in turn cools and dehumidifies air which is blown across the coil).

Refrigerant used to cool the evaporator coil runs in independent piping, usually copper, from the evaporator coil outside to a compressor and condenser unit where the refrigerant is repressurized, cooled, and returned back inside to the evaporator coil as a liquid. The photos (above) show a basement AHU, an outdoor compressor/condenser, and flex-duct in an attic.

In the above-left photo, the basement AHU has been retrofitted with an air conditioning unit which by simple inspection is probably improperly designed and mismatched to the size and air flow character of the original air handler - notice how the A/C plenum is much larger than the blower compartment.

In the above-right photo the compressor unit looks OK on casual inspection but there seems to be no pad, the unit is slightly tipped, and while we can't see the refrigerant lines, that taut electrical wire makes me wonder if there is a lack of extra slack (a loop) in the refrigerant lines to permit movement - a refrigerant leak and system failure may be coming soon.

In the third photo above, this particular flex duct product, one previously produced by Owens Corning(R) is defective and disintegrates on exposure to hot areas. [Owens Corning flex duct failure photo courtesy of Mark Cramer Tampa FL]

Photos of the Horizontal Attic or Crawl Space Air Handler Unit for Central Air Conditioning

Photograph of the air handler unit or AHU for a typical residential attic air handler installationunit for central air conditioning

Attic air conditioning equipment for residential air conditioning systems includes an air handler unit such as the one shown in this photo, combined with an outside compressor/condenser such as the one shown earlier above.

Attic-mounted central air equipment may have different defects and problems than a similar unit located in a lower building floor or basement.

The residential central air conditioning equipment components are the same in an attic unit as a typical basement unit except that they are arranged horizontally rather than vertically.

Horizontal crawl space air handlers are found below homes in some areas and use equipment of the same design as horizontal attic A/C units (shown here).

Watch out: locating air handling equipment or ductwork in wet or moldy areas such as some crawl spaces is asking for an indoor air quality problem. And if access to the air handler in an attic or crawl space is limited, then service of the equipment will also be limited, poor, or more costly.

Photos of Independent Split Systems or Ductless Air Conditioning or Heat Pumps

Photograph of the indoor evaporator and fan unit for a wall-mounted Sanyo split system air residential conditioner

Photograph of the outdoor condenser and compressor unit for the wall-mounted Sanyo split system air residential conditioner shown here

Ductless air conditioning systems do not make use of an air handler connected to duct work to distribute conditioned air the for central cooling and/or heating. These include ductless systems mounted on roofs or in attics and wall-mounted units (shown here) which may typically an indoor fan and evaporator coil to produce cooled and dehumidified air, but which route refrigerant to an outside compressor/condenser unit.

See more details at SPLIT SYSTEM AIR CONDITIONERS & HEAT PUMPS.

Photos of Portable or Ductless Air Conditioning or Heat Pumps

Portable or ductless air conditioning systems such as the units shown above work by exhausting warm room air through a window or flex duct section connected to an outdoor opening. If you use such a unit without providing a warm air exhaust to outdoors the effectiveness of the cooling system is of necessity limited. Condensate produced by cooling the air also needs to be drained by gravity, by emptying a reservoir, or by connecting a condensate pump.

Do not cover the air discharge on these units or the equipment won't work and may even be damaged
The manufacturer recommends unplugging the unit from its electrical connection before servicing
These portable air conditioner units should be connected to a single-outlet electrical circuit. And if electrical power to the unit is interrupted, leave the equipment off for at least three minutes before re-starting.

Photos of Wall convector units for heating and air conditioning

Photograph of wall convector heating and cooling system

Wall convectors are often used for both heating and cooling in commercial installations and high-rise apartment buildings. The unit shown has its own compressor mounted right in the cabinet, visible at lower center in the photo.

Wall-mounted heating and cooling convector installations may be designed with one central heater or cooling system which feeds multiple units with chilled or heated water or possibly refrigerant from a single remote heating and cooling heat pump.

More about wall convector blower fans is found at FAN, AIR HANDLER BLOWER UNIT

Photos of Commercial rooftop-mounted combined air conditioning or heat pump units

Photograph of commercial rooftop mounted A/C system

Rooftop mounted central air conditioning systems may include both the cooling unit (evaporator coil, blower fan, filters) and the compressor/condenser unit in one package.

Rooftop mounted central cooling systems may be smaller packaged systems which blow their cool air down directly into the cooled space through an opening in the roof, drawing return air from a nearby location, or the rooftop cooling system may be connected to duct work which in turn blows down into multiple building areas to deliver cool air, drawing return air from one or more centralized returns. In many commercial installations, the entire area over a suspended ceiling may serve as one giant return plenum through which pass the supply ducts, delivering air to individual supply registers.

While the list above describes the common components of a typical residential air conditioning system, other configurations and packaged units are also in increased use in both residential and commercial installations. Alternative designs may combine all components except for the duct work in a rooftop mounted unit such as the one shown above where it was mounted on a flat roof over offices at a commercial building.

Photos of Window or Wall-Mounted or Portable Room Air Conditioners

Photograph of a window mounted A/C system

Photograph of the outside portion of a window mounted A/C system

The window-mounted air conditioner in these photographs is a small 8,000 BTUh unit but it was installed in a strategic location at the top of a second floor stair. It is able to cool the entire second floor of this home (one large, very well-insulated room) and additional cool air flows down the stairwell to also deliver cool and dehumidified air to the lower floor of this home. The photo of the exterior of this unit shows that there has been some damage to the cooling fins of the condensing coil on the back of the unit, but not enough to warrant action.

Photos of a Home Made Central Air Conditioning System

Do-It-Yourself Home made air conditioning systems can produce some systems that seem to cool the building but at high cost and with building damage, such as this goofy example may actually work but not without problems. This system used a window air conditioner placed in a home's attic.

Manhole ventilation duct (liberated from New York City) was used along with a home made hood attached to the air conditioner to blow cool air into the home through a ceiling register. The air conditioning condensate was collected in the blue plastic kiddie pool seen in the photo, and drained by gravity to a plumbing vent stack.

Nothing about the system was proper, safe, nor very effective, and in addition, the attic moisture conditions were terrible as you can see from the blackened plywood roof sheathing. The system was admirable for its creativity however.

Other home made cooling systems such as evaporative coolers using a simple pan of water in front of a window fan can be effective and inexpensive in hot dry climates such as the southwestern United States

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AIR CONDITIONING & HEAT PUMP SYSTEMS

A/C - HEAT PUMP CONTROLS & SWITCHES
A/C DATA TAGS
A/C - HEAT PUMP CRITICAL DEFECTS
A/C DIAGNOSTIC FAQs
A/C REFRIGERANTS
A/C TYPES, ENERGY SOURCE
AGE of AIR CONDITIONERS & HEAT PUMPS

AIR CONDITIONER BTU CHART
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
  Basement Vertical Central Air Handlers
  Home Made Air Conditioning Systems
  Horizontal Attic or Crawl Space Air Handlers
  Portable Room Air Conditioners
  Rooftop-mounted Air Conditioners / Heat Pumps
  Split System or Ductless Air Conditioners
  Swamp Coolers & Water Cooled Air Conditioners
  Wall Convector Units, Heating / Air Conditioning
  Window or Wall-Mounted or Portable Room Air Conditioners
AIR FILTERS for HVAC SYSTEMS

AIR HANDLER / BLOWER UNITS
APPLIANCE EFFICIENCY RATINGS
BACKUP HEAT for HEAT PUMPS

BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING

BOOKSTORE - Air Conditioning "How To" Books

CAPACITORS for HARD STARTING MOTORS
CAPILLARY TUBES
CHINESE DRYWALL HAZARDS
CIRCUIT BREAKER SIZE for A/C or HEAT PUMP
CLEANING & Legionella BACTERIA
COMPRESSOR & CONDENSING COIL, A/C

CONDENSATE HANDLING, A/C
CONDENSATION or SWEATING PIPES, TANKS
COOL OFF HEAT Thermostat Switch
COOLING CAPACITY, RATED
COOLING COIL or EVAPORATOR COIL
COOLING LOAD REDUCTION by ROOF VENTS
COMBUSTION GASES & PARTICLE HAZARDS
CONDENSATE HANDLING, A/C
CONDENSATION or SWEATING PIPES, TANKS

DATA TAGS on AIR CONDITIONERS
DEFINITION of Heating & Cooling Terms

DEHUMIDIFICATION PROBLEMS
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE

DIAGNOSE & FIX AIR CONDITIONER / HEAT PUMP

DUCT SYSTEM & DUCT DEFECTS
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe
DUST CONTAMINATION FROM HVAC?

EDUCATION, HVAC SCHOOLS
ELECTRIC MOTOR DIAGNOSTIC GUIDE
ELECTRIC MOTOR OVERLOAD RESET SWITCH
ELECTRICAL POWER SWITCH FOR HEAT

ENERGY SAVINGS in buildings
EVAPORATIVE COOLING SYSTEMS
EVAPORATOR COIL or COOLING COIL
EXPANSION VALVES, REFRIGERANT

FAN, AIR HANDLER BLOWER UNIT
FAN AUTO ON Thermostat Switch
FAN, COMPRESSOR/CONDENSER UNIT
FAN CONVECTOR HEATERS - HYDRONIC COILS
FAN LIMIT SWITCH
FAN NOISES

FURNACES WARM AIR HEATING SYSTEMS

GASES, EXPOSURE, TESTING
  Carbon Dioxide - CO₂
  Carbon Monoxide - CO
  METHANE GAS SOURCES
GAS MEASUREMENT TOOLS
GAUGE, REFRIGERATION PRESSURE TEST

HEAT LOSS (or GAIN) in buildings
HEAT PUMPS

HUMIDITY LEVEL TARGET

INDOOR AIR QUALITY IMPROVEMENT GUIDE

INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS
LEED GREEN BUILDING CERTIFICATION

LOST COOLING CAPACITY

MANUALS & PARTS GUIDES - HVAC
MOTOR OVERLOAD RESET SWITCH

NOISY AIR CONDITIONER / HEAT PUMP
NOISE / SOUND DIAGNOSIS & CURE
  Air Leak Noises
  AIR CONDITIONING & HEAT PUMP NOISES

OPERATING COST
OPERATING DEFECTS
OPERATING TEMPERATURES

PORTABLE ROOM AIR CONDITIONERS
PRESSURE READINGS, REFRIGERANT

REPAIR GUIDE, AIR CONDITIONERS / HEAT PUMPS
REPAIR & DIAGNOSTIC FAQs for A/C

REFRIGERANTS
  GAUGE, REFRIGERATION PRESSURE TEST
  REFRIGERANT CHARGING PROCEDURE
  REFRIGERANT DRIERS & FILTERS
REFRIGERANT PIPING & DISTANCES
REFRIGERANT PRESSURE READINGS
SEER RATINGS & OTHER DEFINITIONS
SYSTEM OPERATION
SWAMP COOLERS

THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES

WATER COOLED AIR CONDITIONERS

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.
Thanks to Jon Bolton, an ASHI, FABI, and otherwise certified Florida home inspector who provided photos of failing Goodman gray flex duct in a hot attic.
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