The limitations of visual inspection of A/C systems are described here.
This article series answers most questions about 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.
The chapters a this website describe the basic components of an air conditioning system and then we discuss how to estimate the rated cooling capacity of an air conditioning system by examining various data tags and components. We continue to add to and update this text as new details are provided.
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A home inspector is expected to at a minimum, perform a visual inspection of the cooling system and all of its visually accessible components, and to identify significant or dangerous defects. "Inspect" means "operate" or "turn on" if site conditions do not give the inspector a reason not to operate the equipment.
The ASHI, NAHI, CREIA, TAREI, FABI, CAHI, and other professional home inspection associations set inspection standards as do many U.S. states and Canadian provinces which license and regulate home inspectors.
Home inspection standards generally do not require that equipment be disassembled, tested with instruments (amp probes, refrigerant gas detectors, coolant pressure measurements). In addition, the inspector is not expected to inspect any equipment, component, system, or area of a building if in the inspectors opinion that action is unsafe or is likely to cause costly damage.
"Non-central" air conditioners such as window units and "through wall" units (which are basically the same portable devices) are excluded from inspection by most standards. We would interpret ductless systems such as those shown at A/C TYPES, ENERGY SOURCES to be equipment that should be included in a home inspection as these are substantive, permanent systems and they operate using controls similar to ducted central air systems.
These limitations apply to home inspectors examining cooling systems and heat pumps, especially if the equipment appears to be in dangerous condition (damaged wiring for example), or is in a "shut down" or "seasonally shut down" condition, such as operating a cooling system during low temperature conditions.
While home inspectors may omit certain items from inspection under appropriate conditions, the inspector is still required to explain that omission to the client and, where appropriate, to offer follow-up advice.
Below are offered example home inspection report wording describing typical limitations on the ability of a home inspector to examine the condition of an air conditioning or heat pump system. [Contributions and critique are invited.]
COOLING SYSTEM INSPECTION LIMITATION: We check for normal temperature differential between input and output air, unusual operating noises, visible damage or defects, and a variety of other possible defects. This inspection is not technically exhaustive; a more thorough inspection, also not technically exhaustive, can be performed by a qualified HVAC service professional, and is recommended when any defects or malfunction are suspected.
Here are some examples of warning language we might use in a report.
A system is not considered "not usable" simply because it was shut down, but if it was shut down, not operated, and by visual inspection, has visible major defects, we would go further to explain this condition, even though the system was not turned on.
A home inspector who sees that a system is visibly damaged, missing components, or antiquated, but who uses the escape clause of "it was shut down and not inspected" to say nothing more to his/her client, is not doing the best job for the client.
As the cooling equipment had clearly been shut down and because the weather temperature in the past 24 hours has been below 65 degF. we were not able to test-operate this equipment. Operating cooling system equipment which has been "shut down" without proper preparation risks costly damage to the compressor or other components.
Note: some compressor motors can be seriously damaged by being "slugged" with liquid refrigerant or by lack of good lubrication if the compressor is started in cold conditions.
Some air conditioner units, including heat pumps, are likely to have a heater band installed around the compressor motor to keep its temperature up to operating state in cold weather. If such a system using a motor heater has been left with power off for some time, simply turning it on in cool weather is not enough as the heater would need time to warm up the motor.
The cooling system was shut off at the time of our inspection. By visual inspection we observed these conditions which suggest that the system should not be turned on before it is inspected and if necessary, repaired by an HVAC technician:
We recommend that you make no attempt to turn the air conditioning or heat pump system on before having it examined by
a qualified air conditioning service person.
If replacement of major components is required, repair is likely to involve a significant expense.
Inspection and repair are needed before you can use the system.
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