According to the Carson Dunlop training manual there are some limitations to inspecting your central air conditioning system, which are; you shouldn't test an air conditioner when the ambient air is below 65 degrees F or has been below 65 degrees in the past 24 hours, don't test if the power has been off for at least 12 to 24 hours because compressor could seize, most parts of air conditioner are not visible without removing plates etc which is beyond the scope of a home inspection and the interior cooling coil is normally not visible for inspection.
Central air conditioners operate by using Freon gas between two coils. Cool liquid in the cooling coil contacts warm air of your house and attracts the heat as it boils off from liquid to a gas. The gas is then compress by the compressor to increase temperature from approximately 170 to 230 degrees F which then allows the cooler outdoor air to absorb heat from gas when it is moved through the outdoor coil. This liquid, which has been cooled down to approximately 95 to 110 degrees F, is then restricted by passing through a capillary tube or thermostatic expansion valve which brings temperature back down and then cycle is repeated over and over, cooling down your home in the process.
Another function of the air conditioner unit is to dehumidify the air. This function is performed as air passes over the evaporator coil, cooling air to past the dew point, which converts moisture in the air into condensation. This water is collected in a pan and then drains through condensate line to drain etc.
A properly functioning air condition will drop the ambient air by 15 to 20 degrees F. This will seem much cooler because of the dehumidifying of the homes air. Some air conditioners have a block heater or sump heater that warms the oil and release the gas from the lubricant. This can take from 12 to 24 hours, which is why you cannot just power up a central air condition unit and test right away.
I recently came across a situation where a real estate lady, who was representing both buyer and seller, apparently told buyers not to worry because the air conditioner was in working condition. I had told the clients that I was unable to test unit because ambient temperature was below zero at time of inspection. Imagine the homebuyer surprise when they moved in and the air conditioner was not working. Checking with the agent, they were informed that it was disclosed that air conditioner was working in uneven manner. They maintain that on their final walk through the agent, who represented both buyer and seller, reassured them that the air condition was working. Their A/C tech, who inspected unit for them, informed them that the unit had not been working for up to two years. Now the real estate agent is blaming me, the home inspector, saying her home inspector would have tested unit and also stating that there was no verbal confirmation of air conditioner condition. This is a good example of "cavet emptor" buyer beware. This local agent has left a bad impression on these particular homeowners, who do not feel that she represented their interests. She has also made comments about the home inspection that are unsubstantiated and untrue, but money will make people do strange things. It is so important to get those small details in writing, especially when your agent was originally representing the seller. Let that be a lesson for you.
Air condition compressors come in five different types, which are: reciprocating (piston), scroll, rotary, centrifugal and screw. Residential compressors are normally piston, rotary or scroll types.
Most air conditioners have a 5 minute delay built in to prevent starting unit when high-pressure gas is still in system. These types of air condition usually start up with gas being equal on each side of system. Failing to wait can cause damage to compressor. This is also true for your fridges or freezers, you should always wait 5 minutes before plugging them back in.
The compressor is the guts of the air conditioner and is usually the place where most problems occur. Here are some common problems that are encountered with compressors; Excess noise or vibration, Short cycling, Out of level, Excessive current draw, Wrong breaker size, Wiring too small, Missing electrical shut off, Inadequate cooling.
The life expectancy of an air conditioner can depends on where you live and your climate. They can last as little as 8 to 10 years in hot climates to as long as 15 to 20 years in Northern climates. Many older air conditioners may have had their compressors replaced, which would extend their life span considerably.
Tips Read your contract carefully before signing it so that you understand the rights and obligations of all parties. Never rely on a verbal agreement--agreements must be in writing to be valid.
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