Thermo Scientific Cryo 740 Series, Operating And Maintenance Manual

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7000740r7 Cryo Series 2-1 Thermo Scientific
Section 2
Operation
The liquid level controller installed on the
Cryo Series controls the liquid nitrogen level
between the low and high level sensors.
When the liquid level drops below the low
level sensor, the solenoid opens and the
refilling process starts. The refilling continues
until the high level sensor is reached, or the
solenoid switch is turned off.
If the controller detects an alarm condition,
an audible alarm sounds and the
corresponding High or Low Level alarm
indicator on the controller panel lights.
The audible alarm may be disabled by
pressing the Silence button. However, the
warning light and Alarm indicators remain
lit and audible alarm sounds every 30
minutes until the alarm condition is
corrected.
Note
Low level shut down and open level
probe alarms can not be silenced. After the
alarm condition is corrected, the power
switch must be turned off, then on to clear
the alarm.
When Manual Fill button is pressed, the solenoid opens and unit begins to
fill. The Fill indicator lights.
Power indicator lights when power is applied to the unit and the switch is
turned on.
Figure 2-1. Control Panel