Last edit: 09/01/2026
The doubt
Should the Reset button in a machinery be handled by a safety module, or can it be one of several inputs to the Automation PLC?
The question can be rewritten in a more correct language by asking if the Reset is a Safety Function.
Consideration
In several applications, the reset is a Safety Function and therefore it cannot be routed through the Automation PLC.
The EN ISO 13849-1: 2023 lists the Manual Reset Function among the safety functions:
5.2.2.3 Manual reset Function
The re-establishment of the safety function by resetting of the safeguard cancels the stop command.
If indicated by the risk assessment, this cancellation of the stop command shall be confirmed by a manual separate and intended action (manual reset).
A situation whereby the risk assessment may indicate that the Reset is a Safety Function is when there is a safeguarded area with a risk of Whole Body Access.
A safeguarded robot area is a typical case.
In order to reduce the risk of Whole Body Access, the reset button must meet a few conditions, among which:
– From its position, outside the safeguarded area, there shall be full visibility of the area;
– Requirements stated by EN ISO 13849-1:2023 shall be followed.
The risk of a person being trapped inside the area can be reduced with other methods: for example, with the use of personal keys the operator has to keep with himself.
The reset of a machine tool, since there is no safeguarded area, is not required. If the manufacturer decides to install it anyway, it can be handled as a normal control function, and therefore the signal can be routed to the Automation PLC. In this case it is not a safety function!
Conclusion
When you build your control panel, always ask the colleague who did the risk assessment if the reset buttons have to be routed to a Safety PLC and never give for granted that it is not necessary.
Finally, we point out that IEC 62046, in paragraph 5.6, states that:
Resetting a restart interlock of an ESPE application is always a safety-related function. Measures shall be provided to reduce the probability of the restart interlock being reset by a transient or steady-state fault condition. Such measures can in clude, for example, requiring both a rising and falling edge signal within a defined time (e.g. between 150 ms and 4 s) from a manually actuated reset device.