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UF V (E3) 10/2020 Page 47/119
10.3 Performance during and after power failure and shut down
Standard chamber: During a power supply failure, all controller functions are shut down.
Chamber with option “battery-buffered alarm system”: During a power supply failure the battery maintains
the controller functions. The controller display is dark and can be activated for 5 seconds by pressing any
button. The refrigerating machine is out of operation. The chamber’s refrigerating function can be main-
tained through the CO
2
emergency cooling (option, chap. 21). The zero-voltage relay alarm output (9)
(chap. 14.4.7) is switched for the whole duration of the power failure.
After the power returns or when turned on by hand, all functions return to the same status the chamber had
before power failure. The freezer regulates the temperature to the last entered set point.
All settings and set point values remain in the memory during power failure after power off.
If an alarm has occurred caused by the power supply failure (tolerance range, safety controller etc.), confirm
the alarm. See chap. 14.
11. Safety controller (temperature safety device)
The freezer is equipped with an electronic over temperature safety device. It is designated as the “safety
controller”. This second, electrically independent temperature controller takes over control at a selectable
set point in case of fault. It serves to protect the charging material against excessively high temperatures.
The safety controller is independent of the temperature control system. If an error occurs, it performs a
regulatory function.
Please observe the DGUV guidelines 213-850 on safe working in laboratories, issued by the employers’
liability insurance association (for Germany).
The overtemperature safety controller serves to protect the chamber, its environment and the contents from
exceeding the maximum permissible temperature. In the case of an error, it limits the temperature inside
the chamber to the entered safety controller value. This condition (state of alarm) is indicated visually and
additionally with an audible alert if the buzzer is enabled (chap. 14.3). The alarm persists until the chamber
cools down below the configured safety controller value and the alarm is reset on the controller.
Regularly check the safety controller setting. Set the safety controller set point by approx.
15 °C above the desired temperature set point.
The safety controller only activates after the set-point has been reached once.
The settings of the safety controller are inactive during battery operation (option), open door,
power failure, CO
2
emergency cooling (option). They become functional again following resti-
tution of power supply and/or the restart of the chamber with the main power switch (4).
You can set the safety controller mode to “Limit” or “Offset”.
• Limit: Limit value, absolute maximum permitted temperature value
This setting offers high safety as a defined temperature limit will not be exceeded. It is important to adapt
the safety controller value after each modification of the temperature set-point. Otherwise, the limit could
be too high to ensure efficient protection, or, in the opposite case, it could prevent the controller from
reaching an entered set-point outside the limit range.
• Offset: Offset value, maximum overtemperature above any active temperature set point. The resulting
maximum temperature changes internally and automatically with every temperature set-point change.
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