Energy-saving tip: Check your AC unit

Have your home air conditioner unit(s) checked. The cost of a check-up should be under $50, and can quickly pay for itself in reduced electricity costs. In fact, keeping your air conditioning unit maintained can pay for itself ten times over in one year.

A basic evaluation will include checking the:

• thermostat calibration
• filters
• amperage draw on all motors
• electrical connections, control points, capacitors
• both coils for air flow and dirt build-up
• ductwork for air leaks and proper insulation
  (or you can do this one yourself--see next week's hint)
• main drain and pans (in a condo or apartment, if these overflow, you are responsible for the damages)
• refrigerant (Freon)

The University of Florida's Solar Energy and Energy Conversion Laboratory did some experiments with 3-ton residential air conditioning units, and published the results in the International Journal of Energy Research*.

They found that units operating with less refrigerant than they should have (undercharged units) are incredibly expensive to run. Once refrigerant levels drop below 85% of normal, "performance declines significantly." What's "significantly"? At 85% charge, it would cost you $550 more to run your central air conditioning one cooling season in Houston (and that's based on 2001 cost figures).

Moreover, in a random survey of 22 commercial and residential units, they found that 75% of them were running undercharged, at 85% or less of recommended Freon levels.

A more elaborate tune-up, which will run slightly more, will also include:

• evaluating the safety controls
• lubricating the evaporator fan motor
• checking the rain shield on the condenser fan motor
• removing dust, leaves, and other debris from the fan housing

This last item can be accomplished on some units with a hose, but others have to be partially disassembled.

In either case, if someone claims to have accomplished the task in 15 minutes, they're selling you moonshine, as the saying goes. The Florida folks says that routine maintenance and topping off refrigerant should run about two hours labor and one pound of coolant.