This month I would like to discuss air conditioning inspection. Most of the systems I encounter are split cooling only type with a gas furnace as the air handler or heat pumps.

I typically begin my inspection at the exterior so examination of the outdoor unit (also known as the condensing unit) is first for me. I observe visually for obvious damage or if the unit is out of level. There should be proper clearance around the unit as air flow is important to operate as effectively as possible. I check for a disconnect and that it is accessible without leaning over the unit. If readable I observe the rating plate, checking for maximum fuse or breaker size and minimum conductor size so I can check at the panelboard. I also like to check the BTU size of the condensing unit to be sure it is compatible with the evaporator coil inside the house. If the unit is running I listen for unusual noises and place my hand over the unit to be sure it is dumping heat. If not running I will activate the system and return to the outdoor unit to listen and observe operation. If it is too cool to run the system (straight ac only), I will notify my clients it was not operated and to inquire with the seller regarding performance in hot weather. Of course I still do my visual inspection of the system.

Inside the house I inspect the ductwork where visible. I can always tell when there is a duct blow-off when I enter the attic and it is nice and cool for me. Look for kinks and other defect and check for airflow in every room. I commonly find poor connections in the ductwork leaking significant conditioned air into the attic or crawlspace. I like to let the cooling system run for nearly the entire inspection when weather permits to get a good sense of its performance.

At the air handler I check for proper condensate disposal and secondary protection; usually a pan under the unit or a float cutout switch. Rusting or corrosion is an indication of past leakage that could mean the internal pan is clogged with debris. Of course I check the filter. If possible I like to see the coil inside the air handler, particularly if the filter is missing. These can clog up quickly and significantly reduce the heat transfer and air flow. Remember, cooling depends upon significant air flow over the coils.

I like to perform a temperature differential (Delta-T) test. Depending upon conditions in the house I might let the unit run for an hour or so if it was humid inside (usually vacant houses) when I arrived. The unit needs to remove the latent heat (moisture in the air) before a proper temperature drop can occur. I use a thermometer to check return temperature, then at a supply duct as close to the air handler as possible as there is heat gain in the duct runs, particularly when they are in a hot attic.

Once I am satisfied the unit is operating properly, or I have identified performance issues, I return the thermostat to its original position. I always advise my clients that cooling units and heat pumps require annual service and recommend doing so.

We'll talk next month,

Mike Casey
Kaplan Professional Schools
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