Notes:
(a) For application of tertiary distribution arrangement, see paragraph
2.12.2,Central Chilled Water Systems.
(b) Secondary pumps, P5 and P6, each rated at 50 percent of design flow and
design head, with motors sized for single pump operation. 7.5 HP and larger
pumps shall be of variable speed type.
(c) Maintain 15 percent (minimum) pump flow by use of 3-way coil valve(s).
Alternately, provide a 2-way control valve for CC-3 and a 2 way automatic
bypass valve at CC-3 to provide for an automatic bypass of chilled water when
the coil control valve begins to close. The automatic bypass valve and line
shall be sized to handle 15 percent (minimum) pump flow.
2.12.6 DX REFRIGERATION SYSTEMS
2.12.6.1 APPLICATION: The use of DX refrigeration system is not permitted for
patient care and waiting areas. Use chilled water from a stand-alone chiller
or a central chilled water plant, if available. DX systems are allowed in
non-patient areas such as administrative areas in localities not considered
as high humidity areas. Areas of the country, having above mean annual dew
point temperature of 40-45 degrees are considered high humidity areas.
The DX system should be carefully evaluated under the following situations:
(a) The facility does not have a central chilled water plant with any spare
capacity.
(b) The central chilled water plant shuts down in winter. But a few specific
areas require mechanical cooling.
(c) Connections to the existing chilled water plant could involve extensive
chilled water piping and pumping costs, thereby making use of the existing
chilled water plant impractical.
(d) Whenever the project involves special applications requiring back-up
cooling, for the following areas:
(1) Telephone Equipment Rooms
(2) Elevator Machine Rooms
(3) Central Warehouses. See Article 1.3 for the specific areas within the
central warehouse requiring mechanical cooling.
(e) Can be considered for other areas, when appropriate humidity controls are
made.
2.12.6.2 EQUIPMENT SELECTION: If the capacity range permits, the chiller
selection shall be based on the multiple compressors and refrigeration
circuits to ensure energy conservation and operation flexibility.
2.12.6.3 REFRIGERANT PIPING: Wherever the system configuration involves field
installed piping, the same shall be sized and designed in accordance with the
manufacturer's recommendations. The complete piping layout, including all
accessories, such as double suction risers, solenoid valves, expansion
HVAC DESIGN MANUAL
2-44
HVAC SYSTEMS AND EQUIPMENT
Previous Page
