KB (E4 + E6) 02/2017 page 107/148
17.3 Over- and undertemperature safety controller (temperature safety device
class 3.3) (option)
With this option the chamber is equipped with an electronic over- and undertemperature safety controller.
The combination of overtemperature (class 3.1) and undertemperature (class 3.2) protection is regarded
as a safety device class 3.3 acc. to DIN 12880:2007.
This over- and undertemperature safety controller serves to protect the chamber, its environment and the
contents from exceeding the maximum or minimum permissible temperature. Please observe the DGUV
guidelines 213-850 on safe working in laboratories (formerly BGI/GUV-I 850-0, BGR/GUV-R 120 or ZH
1/119, issued by the employers’ liability insurance association) (for Germany). The safety controller is
functionally and electrically independent of the temperature control system. If an error occurs, it performs
a regulatory function.
The overtemperature safety controller set-point is a maximum temperature value, which the chamber
will not exceed due to the regulatory function of the safety device. This protection against excessively
high temperatures serves to protect the chamber, its environment and the contents. In the case of an
error, the safety controller limits the temperature inside the chamber to the entered safety controller set-
point.
The undertemperature safety controller set-point is a minimum temperature value, which the chamber
will not fall below due to the regulatory function of the safety device. This protection against excessively
low temperatures serves to protect sensitive loads against under cooling. In the case of an error, the safe-
ty controller limits the temperature inside the chamber to the entered safety controller set-point.
Check the setting regularly and adjust it following changes of the set-point or charge.
17.3.1 Safety controller modes
You can select between “Limit (absolute)” and “Offset (relative)” safety controller mode
• Limit: Absolute maximum or minimum permitted temperature value
This setting offers high safety as a defined temperature limit will not be exceeded or fallen below. It is
important to adapt the safety controller set-point after each modification of the temperature set-point.
Otherwise, the limit could be too big 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: Maximum permitted over- or under temperature above/ below the active temperature set point.
The maximum temperature changes internally and automatically with every set-point change.
This setting is recommended for program operation. It is important to check the safety controller set-
point and safety controller mode occasionally, as it does not offer a fix limit value, which would not be
exceeded or fallen below.
Example: Desired temperature value: 40 °C, desired overtemperature safety controller value: 45 °C,
desired undertemperature safety controller value: 30 °C.
Possible settings:
Temperature
set point
Safety controller
mode
Overtemperature safety
controller set-point
Undertemperature safety
controller set-point
40 °C
45 °C 30 °C
5 °C 10 °C
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