Wiring Category 3

A single fault will not lead to the loss of the safety function and whenever practicable, the single fault shall be detected at or before the next demand on the safety function.

To meet the requirement for Category 3, the mirror contact feedback (Mirror In/ Mirror Out) must be monitored by a Preventa XPS module (or equivalent) that performs external diagnostic monitoring of the SILSafety Integrity Level according to standard IEC 61508.* starter’s mirror contact. If the mirror contact does not open on stop, the next restart is prevented for all SIL starters in the SIL group. The safety-related sensor element is wired to a Preventa XPS module (or equivalent). The Preventa XPS module (or equivalent) outputs are wired to the SIL-IN/SIL Common inputs of the SIL interface module.

In case of indirect monitoring, the external monitoring of the group status should look for states 2 or 4 to persist for longer than the actuation time of a SIL Stop. Use the status information to prevent the next restart of the group SIL starters.