M (E3.1) 1/2023 page 70/136
13. Overtemperature protection
13.1 Overtemperature protective device class 1
The chambers are regularly equipped with an overtemperature protective device (bimetallic switch) safety
device class 1 acc. to DIN 12880:2007. It serves to protect the chamber, its environment and the contents
against exceeding the maximum permissible temperature. When a defined cut-off temperature is reached,
the overtemperature protective device turns off the heating.
Cut-off temperature values:
M 56: 330 °C / 626 °F
M 115, M 260, M 720: 350 °C / 662 °F
The message “Overtemperature” is displayed on the controller.
If the overtemperature protective device class 1 has turned off the heating, proceed as follows:
• Disconnect the controller from the power supply for at least 10 seconds (operating the on/off switch (4)
or main power switch (11) or pull the power plug).
• If appropriate, have an expert examine and rectify the cause of the fault.
• Let the chamber cool down
• Restart the chamber.
As soon as the inner chamber temperature after restart is below the defined cut-off temperature of the
overtemperature protective device class 1, the alarm message is deleted automatically.
13.1.1 Message and measures in the state of alarm
The state of alarm is indicated visually and, if the buzzer is enabled (chap. 12.5) there is an additional
audible alert (chap. 12.2). The heating turns off.
In the list of active alarms, a text message indicates the alarm cause. If the audible arm is activated, the
buzzer sounds. Press the Alarm icon icon to mute the buzzer.
Normal display with overtemperature alarm.
Press the Alarm icon
List of active alarms.
Press the Reset alarm icon.
The alarm message “Overtemperature” and the screen header flashing in red color keep displayed on the
controller until pressing the Alarm icon icon and the alarm is reset (controller disconnected from the power
supply for at least 10 seconds) and the inner temperature has fallen below the cut-off temperature value.
Note: When the overtemperature protective device class 1 has deconnected the heater you should discon-
nect the chamber from the power supply and have an expert examine and rectify the cause of the fault.
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