User manual

Operation
14
Auto Restart
When there is a loss of power to the cooling unit and power comes back, the unit will return to its pre-
vious operating status—on if it was on before the power off, off if it was off.
When power returns, the autorestart time—time-selectable: Single Unit Auto Restart (Service Menu,
Options Setup)—controls the start of the unit. The autorestart time runs in a loop, starting the next
unit each time when elapsed, starting with Unit # 1.
Loss of Power Alarm
A Loss of Power Alarm is activated when power is restored after an interruption. If acknowledged, the
alarm resets automatically after 30 minutes. This alarm can be set to different event types (Message,
Alarm or Warning) and can be disabled under menu item Loss of Power (Service Menu, Set Alarms).
Fan Alarm / Fan Protection Settings
The fan operation is protected by two digital devices: motor protection (optional) and a differential
pressure switch. The motor protection monitors for main fan overload and the differential pressure
switch ensures that the blower(s) are moving air. If either protection device triggers, an alarm will be
announced by a buzzer, alarm relay and event to monitoring after an adjustable time-delay (Main
Fan Overload and Loss Of Airflow in Service Menu, Set Alarms).
The time delay at the unit start is always five seconds shorter than the control delay (to avoid short
component starting when the fan is not working). During operation, the fan delay is fixed to
15 seconds.
There are two selection possibilities for both, Loss Of Airflow and Main Fan Overload:
• Shutdown—stops the unit (intended for DX models).
• Disable—stops the humidifier, electrical heaters and dehumidification; allows cooling and
free-cooling only (intended for chilled water models / external cooling).
3.1.2 General Compressor Requirements
Low-Pressure Time Delay
When the compressor starts, the low-pressure input is ignored for a selected period of time based on
the setting of the Low Pressure Alarm Delay (Service Menu, Options Setup). This time is usually set
to 3 minutes on air-cooled units, and to 0 or 1 minute on water cooled units. When this time is
expired, a second timer starts to operate if the low-pressure input is active. This second timer is active
during normal compressor operation to avoid compressor trips due to bubbles in the refrigerant or
other influences creating short trips of the low-pressure switch. The low-pressure switch input is
enabled only if the compressor is operating.
High Pressure Alarm
When the compressor is initially activated, the system will be monitored for a high pressure situation.
When a high pressure situation is detected during the first 10 minutes of operation, the unit will
attempt to correct the problem several times without notification. If the unit is unsuccessful in cor-
recting the problem, an alarm will occur and the affected compressor will be locked off. If high head
pressure alarm trips three times in a rolling 12 hour period, the affected compressor will be locked off.
After the compressor has been running for 10 minutes, if a high head pressure situation is detected,
an alarm will occur and the affected compressor will be immediately locked off without the unit trying
to correct the problem.
NOTE
Loss of power alarm will be activated only on units that had the fan on before power was lost.
NOTE
When the Main Fan Overload alarm is active, the Loss of Airflow alarm is masked out.
NOTE
Low-pressure condition could be read through contacts or through pressure transducers with
threshold setting.