M (E3.1) 1/2023 page 71/136
13.2 Overtemperature safety controller class 2 / 3.1
The chambers are regularly equipped with an adjustable electronic safety controller. It serves to protect the
chamber, its environment and the contents against exceeding the maximum permissible temperature.
Please observe the regulations applicable to your country (for Germany: DGUV guidelines 213-850 on safe
working in laboratories, issued by the employers’ liability insurance association).
Note: The function of the safety controller does not affect the function of the class 1 overtemperature pro-
tection device (bimetallic switch), as both are connected in series. Both signals are therefore required for
the chamber to be operational.
Check the setting regularly and adjust it following changes of the set-point or load.
In the controller menu you can select between a safety controller class 2 (“temperature limiter”) or class 3.1
(“temperature protection”) acc. to DIN 12880:2007:
• The safety controller class 2 must be acknowledged with the OK button before the heating is switched
on again.
• The safety controller class 3.1, on the other hand, switches the heating on again automatically when
the temperature falls below the the selected safety controller set-point.
• Safety controller class 2 (“temperature limiter”)
The safety controller class 2 limits the temperature inside the chamber to the entered safety controller
set-point. In the event of a fault (if this maximum temperature is exceeded) the safety controller com-
pletely turns off the heating until manual reset.
This condition (state of alarm) is indicated visually and additionally with an audible alert if the buzzer is
enabled (chap. 12.5). You can turn off the buzzer with the Reset alarm icon. The alarm persists until
the chamber cools down below the configured safety controller value. The heating is only switched on
again if the class 2 safety controller has been acknowledged with the Reset alarm icon.
If the safety controller class 2 has turned off the heating, we recommend proceeding as follows:
• Disconnect the chamber from the power supply.
• Have an expert examine and rectify the cause of the fault.
• Restart the chamber
• Reset the alarm message
• Safety controller class 3.1 (“temperature protection”)
The safety controller class 3.1 limits the temperature inside the chamber to the entered safety controller
set-point. In the event of a fault (if this maximum temperature is exceeded), it takes over the control to
this value. This condition (state of alarm) is indicated visually and additionally with an audible alert if the
buzzer is enabled (chap. 12.5).
The safety controller keeps control of the chamber until the chamber temperature cools down below the
safety controller set-point value. When the chamber cools down below the configured safety controller
value, the heating is activated again. You can then reset the alarm on the controller.
If the safety controller class 3.1 has taken over control, we recommend proceeding as follows:
• Disconnect the chamber from the power supply.
• Have an expert examine and rectify the cause of the fault.
• Restart the chamber
• Reset the alarm message
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