Water-cooled chiller proposal represents energy savings for ASHRAE 90.1

An estimated annual energy savings of 13% relative to ASHRAE/IESNA Standard 90.1-2004 should result from a proposed addendum regarding air- and water-cooled chillers.

By Consulting Specifying Engineer Staff October 16, 2007

An estimated annual energy savings of 13% relative to ASHRAE/IESNA Standard 90.1-2004 should result from a proposed addendum regarding air- and water-cooled chillers.

ANSI/ASHRAE/IESNA Standard 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, provides minimum requirements for the energy-efficient design of buildings except low-rise residential buildings. Fourteen proposed addenda to the 2007 standard, due out for publication later this year, currently are open for public comment.

Among the addenda is proposed addendum m, which establishes effective Jan. 1, 2010, an additional path of compliance for water-cooled chillers as well as consolidation and new requirements for some of the existing categories. The proposed addendum was developed by a team of Standard 90.1 members, industry manufacturers and energy advocacy groups, including the American Council for an Energy Efficiency Economy, Washington, D.C., and the Air-Conditioning and Refrigeration Institute (ARI), Arlington, Va., and was supported by ARI chiller manufacturers.

Product development for water-cooled chillers in recent years has focused on improving off-design and part-load performance where most of the operating hours occur, said Drake Erbe, chair of the standard’s mechanical subcommittee. Variable speed drives (VSD) technology has advanced and is finding widespread application in water-cooled chillers. The use of VSDs has led to off-design and part-load improvement of the chiller’s performance with efficiencies of up to 30% in integrated part-load value (IPLV).

Under the proposed addendum, an alternative set of efficiency levels, Path B, is established for water-cooled chillers intended for applications where significant time is expected at part load. All Path B chillers must be equipped with demand limiting controls. Under this proposal, compliance with Standard 90.1 can be achieved by either meeting the requirements of Path B or Path A (intended for applications where significant operating time is expected at full load conditions).

However, both full-load and IPLV levels must be met to fulfill the requirements of Paths A or B, according to Erbe.

The proposed addendum also combines water-cooled positive displacement chillers into one category and adds a new size category for centrifugal chillers at or above 600 tons. The air-cooled chiller without condenser equipment type category has been eliminated. All air-cooled chillers without condensers must now be rated with matching condensers.

The minimum efficiencies of air-cooled chillers have also been updated, Erbe said. Efficiencies in the inch-pound version of Standard 90.1 are now expressed in energy efficiency ratio (EER) for air-cooled chillers, kW/ton for water-cooled chillers and coefficient of performance (COP) for absorption chillers to reflect industry practices. Tables 6.8.1 H through J listing minimum full load and non-standard part load value (NPLV) efficiencies of water-cooled centrifugal chillers at non-standard rating conditions have been eliminated and replaced by an algebraic equation. The tables will now be included in the User’s Manual.

This proposal is estimated to save 457.6 GWh of energy per year compared to the requirements of the 2004 version of Standard 90.1. This represents an annual chiller energy savings of 13.3%

Proposed addend m to ASHRAE/IESNA Standard 90.1 is available during its public review period, which ends Oct. 29. To read the addendum or to comment, go to www.ashrae.org/publicreviews