(3) During unoccupied hours, the garage shall be heated in 100 percent
recirculation mode to maintain a minimum of 5 degrees C (50 degrees F).
2.12
REFRIGERATION SYSTEMS FOR AIR CONDITIONING
(See Article 4.11 for Walk-in Refrigerators)
2.12.1 GENERAL
2.12.1.1 SYSTEM TYPES: The refrigeration systems shall be either chilled
water or direct expansion (DX) type. See paragraph 2.12.6 for restrictions on
use of DX system for high humidity areas of the country.
(a) Chilled Water System: Chilled water systems generally use air-cooled or
water-cooled chillers or absorption types. Absorption chillers could also be
used, if it saves energy. Electric chillers come with a variety of
compressors centrifugal, scroll or reciprocating type. Reciprocating
chillers, however, are phasing out slowly.
(b) DX System: These systems use refrigerant throughout between compressor
and cooling coils. Screw, scroll and reciprocating compressors are generally
used for this application.
2.12.1.2 SYSTEM SELECTION: The selection of a specific refrigeration system
requires careful analysis. The following parameters influence the selection:
(a) Life Cycle Cost Analysis of different chilled water systems.
(b) System Capacity, kW (Tons of Refrigeration).
(c) System Application, Examples: Surgical Suites or Regional Office
Buildings.
(d) New System or Addition to Existing System.
2.12.1.3 REFRIGERANT SELECTION: The refrigerant shall be fully compatible
with all local, state, and federal regulations. The refrigeration equipment
selection shall be based on the new EPA approved hydrochlorofluoro-carbon
refrigerants, such as, HCFC 123, HFC 134a, and HCFC 22. The latest versions
of ASHRAE Standards 15 and 34 shall be followed to ensure its full
compliance.
(a) Provide adequate ventilation of the mechanical equipment rooms, and make
provisions for emergency shut down of equipment.
(b) Provide refrigerant vapor detectors and monitors, and alarms local as
well as at ECC. A minimum of two self-contained breathing apparatus shall
also be provided, one inside and one outside the mechanical equipment room.
(c) Low pressure chillers shall be vented to outdoors.
2.12.2 CENTRAL CHILLED WATER PLANT
Design of a central chilled water plant shall be in accordance with the
following criteria:
2.12.2.1 NUMBER OF CHILLERS: The central chilled water plant shall comprise
of at least two chillers, unless the system is to be cross connected to an
existing chilled water plant. In that case, a single chiller may be used. The
HVAC DESIGN MANUAL
2-38
HVAC SYSTEMS AND EQUIPMENT
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