Zone
Zone
SECTION 2: SEQUENCE OF OPERATIONS
Main Chiller Controller Technical Guide
20
Main Chiller Controller Operation
2. Remove the run enable signal from all compressor
modules and economizer modules. The compressors
will run their auto-shutdown sequence and will ignore
any minimum demand level sent from the main
controller.
Compressor Faults
1. All running compressors are continuously monitored
for operating Faults that cause the aff ected compressor
to shutdown. If a fault is detected, the associated
Economizer Module is de-activated until such time
that the fault is corrected and normal operations
resume.
2. If Lead/Lag is the control method, then a compressor
removed from operation can resume operation auto-
matically if the fault is corrected and all signals from
the Turbocor
®
indicate normal operations can resume.
3. If Sequential Operation is the control method, the unit
will not stage above the aff ected controller until the
fault is corrected and the aff ected compressor resumes
normal operation.
4. If three compressors are running and compressor 1 or
2 fault, the remaining compressors will continue nor-
mal operation if they have already staged on. On
sequential systems, the remaining compressors will
not be able to stage past the aff ected compressor.
Condenser Control
Condenser control will manage fan speed of all fans simultaneously
based on the highest pressure ratio from all running compressors.
Startup
1. Startup begins with the activation of the selected
Compressor Circuit Module after the IGV has
opened and the RPM’s are detected.
2. Determine the condenser starting position based on
a reset function with outside air temperature.
3. Apply the condenser start position to all condenser
fan controllers and maintain it through the fan-bank
startup sequence.
4. Activate the condenser fan-banks in a delayed
startup stage based on a settable delay.
5. Maintain the condenser start position for an
additional delay following all banks starting.
6. Continue with modulation.
Modulation
1. Obtain the pressure ratio from each running
Compressor Circuit Module.
2. Using the highest pressure ratio, modulate the
condenser fans to maintain the defi ned pressure
ratio.
3. The modulation sequence does not change with
compressor staging except that added or removed
compressors can change the selection of highest
pressure ratio.
Shutdown
1. When all compressors shutdown, turn off all fan
banks simultaneously when the compressor state
indicates they are fi nished with the shutdown
procedure.
Expansion Valve Control
The expansion valve control is used to regulate the level of coolant
in the tank.
Startup
1. At startup, all expansion valves are initially closed.
2. The starting position is set with the activation of the
selected Compressor Circuit Module, after the IGV
has opened and RPM’s are detected.
3. Hold the starting position for a programmable delay
before entering modulation.
Modulation
Modulation is intended to control the level of refrigerant
in the tank.
1. Modulation runs on a PID loop as the barrel level
can go from 100% full to empty in 30 seconds.
2. The target tank level is based on a combination
of the number of running compressors and the
current demand level in a reset type function.
• Based on the number of compressors running, a
separate pair of settable minimum and maximum
control positions will be used.
