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VD (E3.1) 10/2020 page 88/179
11. Temperature safety devices
11.1 Over temperature protective device class 2 (thermal switch)
The chamber is equipped with an internal temperature safety device class 2.0 acc. to DIN 12880:2007. It
serves to protect the chamber and prevent dangerous conditions caused by major defects of the
chamber. It is electrically independent of the controller (bimetallic switch).
When the fixed temperature of 330 °C is measured at the thermal switch, the overtemperature protective
device turns off the heating. This is the equivalent to an inner chamber temperature of 270 °C uo to
300 °C.
The alarm message “Overtemperature” is displayed on the controller.
If the overtemperature protective device has turned off the heating, proceed as follows:
• Confirm the alarm message on the controller.
• Disconnect the chamber from the power supply (pull the power plug) and let it cool down
• If appropriate, have an expert examine and rectify the cause of the fault.
• Restart the chamber.
As soon as the inner chamber temperature after restart is below the defined cut-off temperature of the
overtemperature protective device of 230 °C, the heating is released again.
11.2 Overtemperature safety controller class 2
The chambers are regularly equipped with an electronic overtemperature safety controller (temperature
safety device class 2 – temperature limiter) acc. to DIN 12880:2007). The safety controller protects the
chamber, its environment and the charging material against exceeding the maximum permissible
temperature. The safety device class 2 is electrically independent of the temperature controller and turns
off the chamber permanently.
In the event of a fault in the temperature controller, the safety controller turns off the vacuum drying oven
permanently, i.e. until manual alarm reset. This condition (state of alarm) is indicated visually and
additionally with an audible alert if the buzzer is enabled (chap. 13.4.1). You can turn off the buzzer with
the OK button / Confirm icon. The alarm persists until the chamber cools down below the configured
safety controller value.
Please observe the DGUV guidelines 213-850 on safe working in laboratories, issued by the employers’
liability insurance association (for Germany).
Check the setting regularly and adjust it following changes of the set-point or charge.
The temperature safety device only activates after the set-point has been reached once.
11.2.1 Safety controller mode
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.
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