chillers shall be identical in size and design, except for the following
considerations:
(a) Part Load Conditions: If the anticipated part load conditions justify the
use of uneven sizes. The designer shall prepare the necessary cooling load
profile demonstrating the need for doing so.
(b) Operating Costs: Do a life cycle cost analysis of the following chillers.
Based on the favorable results for energy consumption and/or electrical
demand charges, a selection of the chiller plant shall be made.
(1) All electric chillers
(2) All absorption chillers
(3) Combination of electric and absorption chillers
2.12.2.2 CHILLER CAPACITY: The maximum capacity of a single chiller unit
shall not exceed 3520 kW (1,000 tons) for a central chiller plant. The
cooling loads for the surgery suites (Paragraph 2.12.7) and the animal
research areas (Paragraph 2.12.8) shall not be included in the central plant
capacity computations. These both areas shall have their own dedicated
chillers.
2.12.2.3 CHILLER PERFORMANCE: The electric, water-cooled, centrifugal and
rotary-screw chillers shall be scheduled on drawings in accordance with the
ARI Standard 550/590-98 for the lowest full load KW/ton which can be met by
at least three manufacturers. Executive Order 13123 and FAR Section 23.704
requires that products be purchased in the upper 25 percent of energy
efficiency. Accordingly, DOE recommends following chiller efficiencies, which
are based on standard reference conditions, specified in ARI Standard
550/590-98. The designer however, shall document the values selected with
calculations, manufacturer's selection data, and any other relevant
information for actual (non-standard) design conditions for a specific
project and the efficiencies could vary from values shown below.
Table 2-19
Chiller Efficiencies for Standard ARI Conditions
Chiller Type
Full Load-kW/Ton
IPLV-kW/Ton
Centrifugal
0.59 or Less
0.52 or Less
150-299 Tons
Centrifugal
0.56 or Less
0.44 or Less
300-2000 Tons
Rotary-Screw
0.64 or Less
0.49 or Less
150 Tons or Greater
2.12.2.4 STANDBY EQUIPMENT
(a) Chillers: Standby refrigeration equipment or arbitrary safety margin as a
spare capacity is not required. See Article 1.3.15 for air handling capacity.
Chiller(s)shall be sized based on this capacity.
(b) Pumps: When two chillers are used to handle the total cooling load, one
condenser water and one chilled water pump shall be provided to act as
standby. When three or more chillers are used, no standby pumps will be
required.
HVAC DESIGN MANUAL
2-39
HVAC SYSTEMS AND EQUIPMENT
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