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AIR CONDITIONING & HEAT PUMP SYSTEMS
A/C - HEAT PUMP CONTROLS & SWITCHES
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR FILTER EFFICIENCY
AIR FILTERS, FIBERGLASS PARTICLES
AIR FLOW MEASUREMENT CFM
APPLIANCE DIAGNOSIS & REPAIR
APPLIANCE EFFICIENCY RATINGS
BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BOOKSTORE - Air Conditioning "How To" Books
CAPACITORS for HARD STARTING MOTORS
CLEANING & Legionella BACTERIA
CHINESE DRYWALL HAZARDS
CONDENSATION or SWEATING PIPES, TANKS
DEFINITION of HEATING & COOLING TERMS
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM & DUCT DEFECTS
DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe
DUST, HVAC CONTAMINATION STUDY
ELECTRIC MOTOR OVERLOAD RESET SWITCH
EVAPORATIVE COOLING SYSTEMS
FAN LIMIT SWITCH
GAS EXPOSURE EFFECTS, TOXIC
GAS DETECTION INSTRUMENTS
HEAT LOSS (or GAIN) in buildings
HEAT LOSS (or GAIN) INDICATORS
HEAT LOSS R U & K VALUE CALCULATION
HEATING SMALL LOADS
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS, A/C SYSTEMS
LEED GREEN BUILDING CERTIFICATION
LOST COOLING CAPACITY
LOW VOLTAGE TRANSFORMER TEST
MOTOR OVERLOAD RESET SWITCH
MOLD in AIR HANDLERS & DUCT WORK
OPERATING COST, AIR CONDITIONER
OPERATING DEFECTS, AIR CONDITIONING
REPAIR GUIDES A/C / HEAT PUMP
REPAIR & DIAGNOSTIC FAQs for A/C
THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES
WATER COOLED AIR CONDITIONERS
WINDOW / WALL AIR CONDITIONERS
WINDOW / WALL A/C SUPPORTS
Guide to types of air conditioners & cooling or heat pump systems: 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.
This article series 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.
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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.
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.
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.
See details at EVAPORATIVE COOLING SYSTEMS.
Evaporative Coolers - Rooftop Cooling 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.
We discuss swamp coolers & evaporative coolers in 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
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]
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.
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.
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.
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
Alternative HVAC 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.
Details are at ROOFTOP HVAC UNITS
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.
At AIR CONDITIONER BTU CHART we describe how to determine the BTU capacity you'll need when choosing a window ari conditioner.
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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