As per the Carson Dunlop training manual there are a few limitations to inspecting central AC systems and these include not testing them when the indoor air is lower than 65 degrees Fahrenheit or when it has been below this temperature at any point over the past 24 hours.
Do not test it if the home power supply has not been functional within the last 12-24 hours given that the compressor might seize and you should note that many AC parts are not easy to see without removing certain components.
This is more than most homeowners can do safely on their own and the interior cooling coil is rarely accessible for this type of inspection.
Central systems function by using Freon that passes between two coils. The cool liquid that is found in the coil contacts helps to heat the air in your home and attracts more heat while boiling off from a liquid state and turning into gas.
The compressor then compresses this gas to raise its temperatures as high as 230 F, after which the cool outside air can absorb heat from this gas while passing through the outside coil.
The liquid cools to a temperature of about 100 F and is then restricted by either a thermostatic expansion valve or a capillary tube that lowers the temperature, thereby creating a cycle that is continuously repeated so that your home is cooled.
These systems also have the ability to dehumidify the indoor air. This is done while the air moves over the evaporator coil, which converts indoor moisture into condensate. This condensation is captured in a pan and drained.
An AC unit that is functioning properly can lower the indoor air by as much as 20 degrees F. This will often seem far cooler due to the dehumidification that occurs during this process.
Certain systems have block heaters or sump heaters that heat oil instead and then release gas from this lubricant. This process can take anywhere between 12 hour and 24 and thus, it is not possible to simply turn on a central AC and test it right off.
I was recently in touch with a real estate agent who represented both the seller and the buyer and who told the prospective buyer to not worry because the AC system was working fine.
I told the client that it was not possible to test the unit given that the room temperature was below zero when the inspection was supposed to be performed.
Imagine how surprised the buyer was upon moving in to find that the system did not function properly. Once they referred to the agent, they learned that the seller had disclosed that the AC was not performing as it should.
They emphatically attest to the fact that the agent, during the walk-through, had assured them that this equipment was in proper working order. The air conditioner technician who performed the inspection said that it had been about two years since the system had worked.
Now the agent tried to place the blame on me, stating that as a home inspector I should have tested this equipment and that she had never verbally confirmed that the unit was working. She made a very bad impression on the buyers, who believe that she failed to represent their best interests.
She additionally made false statements about the home inspection, but money can make people do a number of unexpected things. These small details are vital to get in writing, especially if your agent is representing the seller as well. This is one of the most important things to know about home inspections and your air conditioner.
There are five different types of AC compressors. These are piston, rotary, scroll, screw and centrifugal. Residential systems typically have scroll, rotary or piston compressors.
A lot of these systems also have a built-in 5 minute delay that prevents people from starting their units up when there is still high pressure gas in them. Without this waiting period, the compressor can get damaged.
Avoid putting your unit directly in the sun, particularly on your home’s south side. You should also clean your indoor coils on a regular basis with a brush or a vacuum cleaner. Read the manual for details on starting it up and operating it properly.
Additionally, make sure that curtains, rugs, carpets or furnishings are never blocking the vents and registers.