Large air handlers are usually located in their own mechanical rooms and are easily accessible for maintenance. The engineering staff should be vigilant for air leaks at flex connections, filter sections, and duct joints. It’s especially urgent to stanch air leaking after the filter section, as this allows dirt and dust into the fan, coils, and other critical parts of the air handler.
Fan belts need to be inspected for tightness and wear, so the full motor power reaches the fan, and an offset or imbalance does not cause extra wear on the motor or fan bearings. The fan and motor should be lubricated according to the manufacturer’s guidelines for optimum performance.
It’s also important to change the return-air filter regularly. Not only is the filter efficiency reduced when the filter media gets dirty, but also it’s harder for air to flow through it, and the air volume is therefore diminished. As a result, the air handler must operate longer to supply a fixed volume of conditioned air to a room to maintain conditions. This extra operating time is an unnecessary expense that can be avoided by changing out filters regularly.
An economical way to check filter status is to install pressure fittings on either side of the filter bank in the ductwork. A manometer connected to the fittings then measures the pressure differential across the filter. Filter manufacturers publish tables that show when to change out filters according to manometer readings. Following these guidelines minimizes energy use, reduces wear on the fan motor, and results in the filtration of the most particles from the airstream at the least cost.
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Excerpt from Energy Conservation Projects.