The Premium Economizer: An Idea Whose Time Has Come

Reid Hart, Dan Morehouse, and Will Price, Eugene Water & Electric Board

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Abstract

Several field studies have found that more than half of outside air economizers on packaged rooftop cooling units are not providing optimal savings, either because dampers or controls have failed, changeover is set incorrectly, or the improper type of controls for the local climate have been installed. Analysis of economizer operation indicates that, at best, only onethird of potential savings is being achieved. Eugene Water & Electric Board (EWEB) has developed “premium” economizer requirements that result in increased economizer savings in the field. Meeting the stricter requirements is rewarded by larger utility rebates.

A brief literature review of packaged rooftop cooling unit studies is followed by results from a full cooling season field test of ten packaged units equipped with either standard or premium outside air economizers. Extended field monitoring shows that properly operating premium economizers provide more savings than standard economizers. Results also show that better commissioning is required to improve economizer reliability. Three years of utility program experience in providing rebates for a “premium” economizer are also discussed.