ETL 1110-1-181
12 Jan 98
Appendix B
Efficiency Comparisons
B-1. BACKGROUND. The procurement of liquid chillers is very difficult
when trying to specify the best applicable energy efficiency.
Efficiencies of liquid chillers vary greatly based upon a number of
different factors. Some of the factors include:
a. Chiller type.
b. Site specific conditions (i.e., outdoor design temperatures,
supply water design temperatures, etc.).
c. Commercial availability.
d. Heat recovery.
e. Refrigerant type (i.e., R-22, R-123, R-134a, etc.).
B-2. ENERGY EFFICIENT PRODUCTS. To encourage the procurement of energy
efficient products where practical and cost effective, the President of
the United States signed into law Executive Order 12902 on March 1994.
The key items in the Executive Order which deals with the procurement of
energy efficient products by federal agencies is presented below. The
efficiency values presented in the designer's notes of the Corps of
Engineers Guide Specification (CEGS) 15650 "CENTRAL REFRIGERATED
AIR-CONDITIONING SYSTEM" were developed based upon Executive Order
12902.
"Section 507.(a).(2) To further encourage a market for highly-
energy-efficient products, each agency shall increase, to the
extent practical and cost effective, purchases of products that
are in the upper 25 percent of energy efficiency for all similar
products, or products that are at least 10 percent more efficient
than the minimum level that meets Federal standards. This
requirement shall apply wherever such information is available,
either through Federal or industry approved testing and rating
procedures."
B-3. ENERGY PERFORMANCE TERMS. Efficiency rating procedures for liquid
chillers are defined in ARI 550, ARI 560, and ARI 590 as applicable.
The following paragraphs are explanations of typical terms used by ARI
to define efficient ratings of liquid chillers.
a. Coefficient of Performance (COP). The COP rating of a liquid
chiller is equal to the net equipment cooling capacity divided by the
total power input to the unit, including controls. COP values are
dimensionless.
b. Energy Efficiency Ratio (EER). The EER rating of a liquid
chiller is equal to the net equipment cooling capacity divided by the
total power input to the unit, including controls. EER values are
expressed in Btuh/Watt. EER is typically used to rate the cooling
efficiency of a liquid chiller running at full load conditions.
c. Integrated Part-Load Value (IPLV).
The IPLV rating of a liquid
B-1
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