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1 : Machine safeties evaporator pump
2 : Condenser water pump
3 : Waterflow chilled water temp, guide vanes, refrigerant pump, and tower fan control
4 : Refrigerant pump
5 : Compressor, compressor on time, service on time
6 : 15-minute start-to-start
7 : 2 minute stop-to-start
8 : Elapsed time
9 : Compressor running
A : START INITIATED: Pre-start checks are made; cooler pump started.*
B : Condenser water pump started (5 seconds after A).
C : Water flows verified (30 seconds to 5 minutes maximum af-ter B). Chilled water temperatures checked against
control point. Guide vanes checked for closure. Refrigerant pump started; tower fan control enabled.
D : Ref pressure verified (15 seconds minimum, 300 seconds maximum after C).
E : Compressor motor starts; compressor ontime and service ontime start, 15-minute inhibit timer starts
(20seconds after D), total compressor starts advances by one, and the num-ber of starts over a 12-hour period
advances by one.
F : SHUTDOWN INITIATED — Compressor motor stops; compressor ontimeand service ontime stop, and 2-
minute inhibit timer starts.
G : Ref pump and cooler pumps de-energized (120 seconds after F).Condenser pump and tower fan control may
contin-ue to operate if condenser pressure is high. Cooler pump may continue if in RECYCLE mode.
O/A : Restart permitted (both inhibit timers expired: minimum of 15 minutes after E; minimum of 2 minute after F).
* : Autorestart after power failure timing sequence will be faster.
Fig 36 – Control Timing Sequence for Normal Start-Up
Prestart check / alert - alarm condition *
STARTS IN 12 HOURS >= 8 (not counting recycle restarts or auto restarts after power failure)
CONDENSER PRESSURE >= COND PRESS OVERRIDE /186.2kPa
Number of recycle restart in the last 4 hours is greater than 5
COMP BEARING TEMP >= COMP BEARING ALERT/ 5.6°C
COMP MOTOR WINDING TEMP >= MOTOR TEMP OVERRIDE / 5.6°C
COMP DISCHARGE TEMP >= COMP DISCHARGE ALERT/ 5.6°C
EVAP_SAT < Evap. trip point** + EVAP OVERRIDE DELTA T OR
EVAP REFRIG LIQUID TEMP < Evap. trip point + EVAP OVERRIDE DELTA T
NOTE: Evap. trip point = 0.56°C(water) or EVAP REFRIG TRIPPOINT(brine)
ACTUAL LINE VOLTAGE <= UNDERVOLTAGE THRESHOLD
(Not applicable for Rockwell UM VFDs)
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