Air Conditioning: Common Sense Saves Energy Dollars

In keeping with our theme of saving money and managing in the economic re-set, our friend Gary Xavier weighs in with some timely advice on Air Conditioning. We'll have a few more of these topics over the next couple of weeks, just in time for cooling system seasonal maintenance.

Building owners and managers often hire a service contractor to perform repairs and maintenance on their air conditioning and refrigeration systems. While this is a viable option for buildings where the maintenance department is not equipped to fully service their cooling equipment, there are preventive maintenance items that can often be addressed in-house, which lead to better system performance, lower energy consumption, and more reliable service with fewer breakdowns – all resulting in cost savings to the building owner.

Filters, Filters, Filters

If a system has a filter, the filter needs routine attention. Air conditioning (comfort cooling) systems use filters to provide a modicum of cleaning to the air supply, and also to keep the evaporator coil form becoming loaded with contaminants carried in the air stream. Refrigeration systems most generally do not use filtered evaporator coils.

The filter’s job is to catch particulate matter and hold it, while still allowing air to pass through. As the filter holds more and more debris, however, the air flow is reduced, often to a point of virtual non-existence. Many air conditioning system problems can be traced to a dirty filter. As the filter plugs up, the lack of air flow reduces the amount of cooling occurring, resulting in a lowering of the efficiency of the unit. In addition, the unit must run longer to accomplish the task of cooling the conditioned space to the desired temperature, which it often cannot attain.

Dirty filters thus result in higher operating costs and more frequent system failures, both costing the building owner money.

Filter maintenance can often be performed by building maintenance staff even in situations where an outside contractor is used for system repair. Following the manufacturer’s specifications for filter type and replacement frequencies is important, as is establishing a reliable, consistent method of determining when each filter should be cleaned or replaced.

According to ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc.) standards, viscous impingement filters - the type commonly used in heating and cooling systems – should be changed when the operating resistance through the filter reaches 0.5 inches of water column.

Air-handlers are often equipped with magnehelic gauges to measure the drop in pressure through the filter, allowing the service person to simply read the gauge on a regular basis, and replace the filter when the pressure drop exceeds the recommended limit. Smaller systems, however, such as rooftop units and room air conditioners have no such mechanism, leaving the service person to decide if a filter change is necessary.

Small system filters are often changed on frequency alone, such as every 30 days; or on their appearance to the technician during routine maintenance. Most equipment manufacturers can offer specific guidelines for their systems, and filter distributors can often be of assistance in setting up a preventive maintenance schedule.