70 Product Manual PM WSC/WDC
5. Controller shall be able to limit motor amps from 30% to 100 % of RLA based on a
keypad entry or by a remote 4-20mA DC signal.
6. The controller shall be able to reset chilled water temperature by controlling return
chilled water temperature or from a remote 4-20 mA DC signal. The amount of reset
shall be adjustable.
7. Soft loading shall be provided to prevent the unit from operating at full load during
pulldown if desired.
8. A time clock shall be incorporated to allow daily timed starts and stops and to allow
for holidays and weekends.
9. The control system shall have automatic restart after a power failure and not require
a battery backup for memory continuity. A battery shall be provided for the time
clock only.
10. The controller shall be capable of starting and stopping chilled and condenser water
pumps. It shall also be capable of four-step control of cooling tower fans and
provide an analog output for a tower bypass valve.
11. The microprocessor shall be capable of communicating to other units or a PC using a
twisted pair communication interface of RS-232 (100 feet) or RS-422/485 (5000 feet) or
with a 9600 baud modem.
2.5. MISCELLANEOUS ITEMS
A. Pumpout System: The unit shall be equipped with a pumpout system complete with a transfer
pump, condensing unit, and storage vessel constructed according to ASME Code for Unfired
Pressure Vessels and shall bear the National Board stamp. If the design of the unit allows the
charge to be transferred to and isolated in the main condenser, then a pumpout system is not
required. Transfer of refrigerant charge shall be accomplished by either main compressor
operation, migration, or gravity flow. Isolation shall be accomplished with valves located at
the inlet and outlet of the condenser. The main condenser shall be sized to contain the
refrigerant charge at 90°F according to ANSI-ASHRAE 15.A.
B. Purge System (HCFC-123 Chillers Only):
1. The chiller manufacturer shall provide a separate high efficiency purge system that
operates independently of the unit and can be operated while the unit is off. The
system shall consist of an air-cooled condensing unit, purge condensing tank,
pumpout compressor and control system.
2. A dedicated condensing unit shall be provided with the purge system to provide a
cooling source whether or not the chiller is running. The condensing unit shall
provide a low purge coil temperature to result in a maximum loss of 0.1 pounds of
refrigerant per pound of purged air.
To Next Page
Loading...
Need help?
General
