78 Product Manual WHR-2
The system shall stage the unit based on the leaving water temperature. Safeties
controlled by the microprocessor include oil differential pressure, motor
protection, high pressure, loss of refrigerant, loss of water flow, freeze protection,
and low refrigerant pressure. Controls shall include auto/stop switch, chilled
water setpoint adjustment, anti-recycle timer, and digital display with water
temperature and setpoint, operating temperatures and pressures, and diagnostic
messages. The following features and functions shall be included:
1. The LCD type display shall have a minimum of 32 characters with all
messages in plain English. Coded messages are not acceptable.
2. Critical parameters shall have their own section of control and be
password protected.
3. Resetting chilled water temperature by either controlling the return
chilled water temperature or by a remote 4-20mA DC signal.
4. A soft load function to prevent the system from operating at full load
during the chilled water pulldown period.
5. An electronic time clock to allow programming of a yearly schedule
accommodating weekends and holidays.
6. Auto restart after a power failure, not requiring external battery back-up
or auxiliary power for maintaining program memory.
7. Safety shutdowns shall be date and time stamped with system
temperatures and pressures recorded. A minimum of six previous
occurrences shall be kept in a revolving memory.
8. Start-to-start and stop-to-start timers to provide minimum compressor
off-time with maximum motor protection.
9. Capability of communication with a PC or remote monitoring through a
twisted pair RS-232 interface.
10. Lead-lag by manual selection or automatically by circuit run hours.
11. Continuous diagnostic checks of unit operation to provide a pre-alarm
signal in advance of a shutdown allowing time for remedial action to be
taken.
F. The following options are to be included:
• Refrigerant and oil pressure gauges for non-microprocessor controls.
• High return water thermostat to keep compressor unloaded with high
startup water temperatures. Contractor to field mount sensor and field
wire to control panel.
• Hot gas bypass on all circuits.
• Chilled water flow switch to be field mounted in the chilled water line
and field wired to terminals in the control panel.
• R-I-S or spring vibration isolators for field installation per plans.
• Disconnect switch field installed.
• Acoustical compressor enclosures.
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