Air Conditioning Repair and the Home Inspector
Air conditioning needs repair from time to time. Some air conditioning repair requires a professional but there are tasks that the average homeowner can attend to. This article helps the reader familiarize himself with system components and basic operation and presents a simple home inspection checklist of tests for determining what air conditioning repair is required.
To repair your air conditioning you first need to understand its design and operation. There are four main air conditioning components: a blower, an evaporator coil, a condenser coil (encased with a compressor and its own fan), and the distribution system of vents and ducts. Repair tends to focus on the condenser and sometimes the evaporator. The blower and evaporator coil (which perform the cooling function) are housed together indoors, often inside the furnace (perhaps separated by the heat exchanger). The condenser unit is outside, where it expends heat removed from indoors. Freon, the chemical properties of which make it a good facilitator of heat relocation, is piped in a closed loop from evaporator to compressor to condenser and back to evaporator.
Freon temperature at each phase in the loop is a good indicator of whether the air conditioning needs repair, and taking its pulse is a common home inspection checklist item. Prior to evaporation, the Freon is a low-pressure liquid at about 20°F. After evaporation it's a gas around 50°F. The compressor raises Freon temperature to about 170°F. Condensation liquefies the Freon, reducing its temperature to about 100°F, but still under relatively high pressure. Finally, an expansion device lowers both pressure and temperature to 20°F again. Any of these temperatures varying significantly from the given values means the air conditioning is malfunctioning and needs repair.
Localized air conditioning (window unit) follows the same principle (condenser on the outside, evaporator on the inside) and repair is more straightforward. Evaporative coolers are a kind of localized air conditioning, but repair of them is beyond the scope of this article.
Approaching Air Conditioning Repair
A professional inspection report includes results from three simple tests that you can perform. First, measure the temperature at the air return to the blower, then measure the temperature at a register; the difference should be between 14° and 22°F. Second, drape a piece of yarn in front of all the registers; there should be enough airflow to make it flutter. Third, place a tissue against the air return; there should be enough pull to hold it in place. Failure of the air conditioning on any of these tests calls for some level of repair.
If there's an airflow issue, inspect your ducts for leaks. Also, if air conditioning ducts go through non-conditioned areas un-insulated, add this fix to your repair list to prevent moisture condensation.
While the air conditioning is running, listen and feel for leaks from the blower compartment, which should be sealed. Make repairs as needed. Then turn off the air conditioning and open the compartment to examine the evaporator coil. A buildup of frost or ice on the coil is a sign of needed repair. This coil also generates condensate; check that the condensate has not overflowed and drains properly.
The final set of tests for the inspection for air conditioning repair takes places with the condenser outside. Here, deference to a heating and air conditioning professional may be wise. Listen for unusual noises, and look for water damage and damage to pipes and hoses. Make sure poor condenser placement hasn't caused damage to proximal structures or components, or vice versa.
Keep the air conditioning running and check the temperature of the two Freon lines. The liquid line (copper and pencil-sized) should be about 20° warmer than outdoor air temperature. The suction line (hot-dog-sized and insulated) should be the temperature of ice water. Variance from these temperatures implies a dirty condenser coil and calls for repair.
If the air conditioning runs continuously or it turns on and off in rapid succession (called short cycling), the compressor is probably overheating and underperforming. Repair is called for.
Help with Air Conditioning Repair
If you feel overwhelmed, schedule a home inspection or call a professional HVAC serviceman to help with your air conditioning repairs.