OM Centrif Micro ΙΙ-5 97
Change Setpoints
Set points are easily changed on the Operator Interface Touch Screen (OITS). A complete
description of the procedure begins on page 24. Set points can also be changed in the unit
controller but this is not recommended except in an emergency when the OITS is unavailable.
Alarms
A red ALARM light in the lower middle of any screen is illuminated if there is an alarm. If the
optional remote alarm is wired in, it too will be energized.
There are three types of alarms:
• FAULT, equipment protection alarms that shut a unit or compressor off.
• Problem, limit alarms that limit compressor loading in response to an out-of-normal condition.
If the condition that caused a limit alarm is corrected, the alarm light will be cleared
automatically.
• Warning, notification only, no action taken by controller.
Any type will light the ALARM light. Procedures for dealing with alarms are shown below:
1. Press the alarm light button. This will go directly to the ACTIVE ALARMS screen.
2. The alarm description (with date stamp) will be shown.
3. Press the ACKNOWLEDGE button to recognize the alarm.
4. Correct the condition causing the alarm.
5. Press the CLEAR button to clear the alarm from the controller. If the fault condition is not
fixed, the alarm will continue to be on and the unit will not be able to be restarted.
Component Failure
Chiller Operation without the Operator Interface Panel
The Interface Panel communicates with the unit and compressor controllers, displaying data and
transmitting touch screen inputs to the controllers. It does no actual controlling and the chiller can
operate without it. Should the Touch Screen become inoperable, no commands are necessary for
continuing unit operation. The unit controller can be used to view operational data and to change
setpoints if necessary.
Chiller Operation without the Unit Controller
The Touch Screen receives most of its operational data from the unit controller and if the unit
controller is not operational considerable data will be absent from the screen. Tower control of
fans and/or bypass valve will be disabled and tower operation will be interrupted and require
manual intervention to continue operation.
Standby Power
It is essential that any centrifugal chiller connected to standby power come to a complete stop
before being restarted on grid power. This is usually not an issue when running on grid power and
experiencing a grid power failure since the chiller’s control will shut down the chiller and
disconnect it from the power source for the stop-to-start setpoint time. It will have come to a
complete stop before restarting.
Under any circumstance, attempting to switch back and forth from regular grid line power and
auxiliary power while the compressor is running can result in extreme transient torque that will
severely damage the compressor.
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