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SAVING ENERGY DOLLARS

Economizer:

Economizers are notorious wasters of energy. If you think you can adjust the outside air damper to 10% fresh air by eye, you could be 30 to 40 percent off. Here is an easy way to save energy and improve building comfort:

Allow the unit to run to stabilize the outside air and return air Temperatures and dampers.
With a reliable thermometer measure Outside Air Temperature (OAT), Return Air Temperature (RAT) and Mixed Air Temperature (MAT).
Decide on the percent of Outside Air Desired (OAD).
Calculation:

Subtract (RAT) from (OAT).
Multiply the results by the percent of (OAD).
Add the (RAT) to the results of “b” = Mixed Air Temperature required for the percent of Outside Air Desired.

Example:

OAT = 45˚, RAT = 65˚, OAD = 10 %

Mixed Air Temp. required = [ (45 – 65) x .10 ] + 65 = ( -20 x .10 ) + 65 = -2 + 65 = 63˚

63˚ = Mixed Air Temperature required to have 10% Outside Air

After measuring the Mixed Air Temperature, if it is different from the (MAT) calculated, readjust the minimum Outside Air Damper setting to obtain the desired Mixed Air Temperature. This adjustment is usually made with a minimum position switch or an electronic command.

Recheck conditions periodically to keep the desired amount of Outside Air for maximum comfort and energy efficiency.