Product data

Control sequence
To start: Push Start button — Start initiated; all safeties
are checked to see that they are satisfied (if one is not, an
indication of thefaultwillbedisplayedandthestartaborted).
The signal is sent to start the chilled water pump. After
5 seconds, the signal is sent to start the condenser water
pump.
The microprocessor then puts the start on hold. It checks
if water flows are established. If not satisfied, it will continue
to monitor water flows according to the adjustable setting
(30 seconds to 5 minutes). If satisfied, it checks the chilled
water temperature against the control point, enables tower
fan control, and checks the slide valve decrease timer (to
verify that the slide valve is in the unloaded position).
Iftheabove checks are satisfied, the microprocessor sends
the signal to start the compressor motor. It monitors the
motor acceleration time and if it is excessive, aborts the
start.If the starterfails to transitiontorun, the startis aborted.
Compressor ontime and service ontime start.
Once started: Phase reversal conditions are monitored to
verify proper rotation of the compressor rotors. The
microprocessor initializes the primary restart protection
(15 minutes — start to start). The slide valve opens in a soft
loading mode and is then transferred to the capacity con-
trol mode.
To stop: Push Stop button — A signal is sent to deener-
gize the compressor motor. Compressor ontime and service
ontime stop. The secondary restart protection (1 minute
stop-to-start) is initialized, and the slide valve decrease timer
is activated.
The microprocessor verifies that power to the compres-
sor is off and, after 30 seconds, sends the signal to deen-
ergize the chilled water pump. (If shutdown was caused by
the low load recycle algorithm, the chilled water pump will
continue to run.) Condenser water pump and tower fan may
continue to operate if condenser pressure is high.
Restart: Restart is permitted after the slide valve timer
and the primary and secondary start protection timers have
expired (a minimum of 15 minutes after the compressor
starts and a minimum of 1 minute after the shutdown is
initiated).
CONTROL SEQUENCE
A—START INITIATED: Pre-start checks are made;
chilled water pump started
B—Condenser water pump started (5 seconds
after A)
C—Water flows verified (30 seconds to 5 minutes
maximum)
D—Chilled water temperature checked against
control point; tower fan control enabled; slide
valve decrease timer checked to verify slide
valve position
E—Refrigerant type verified (up to 3 minutes
after D).
F—Compressor motor starts; phase reversal con-
ditions monitored; compressor ontime and ser-
vice ontime start; 15-minute inhibit timer starts
(10 seconds after E)
G—Shutdown initiated: Compressor motor stops;
compressor ontime and service ontime stop;
1-minute inhibit timer on PSIO Software Version
13 and higher; slide valve decrease activated
for 1 minute
H—Chilled water pump deenergized (30 seconds
after G); condenser pump and tower fan control
may continue to operate if condenser pressure
is high; chilled water pump may continue if in
RECYCLE mode
I—Slide valve decrease timer expires (3 minutes
after G)
O/A — Restart permitted (both inhibit timers expired)
(minimum of 15 minutes after F; minimum of
1 minute after G)
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