What the AC-15 and AC-12 ratings mean for your control circuit
The 3RH2911-4HA30: This auxiliary switch block carries two distinct current ratings depending on the load type. The AC-15 values govern the real-world switching of contactor coils and solenoids — the inrush current can be 5–10× the sealed current, and the contact must weld-free through that. The AC-12 rating is the thermal continuous current ceiling; use it for sizing the contact for purely resistive loads.
Mounting and contact configuration
The 3RH2911-4HA30 snaps onto the front of Siemens SIRIUS contactors in frame sizes S00, S0, S2, and S3 — no tools needed for attachment. It provides 3 normally-open instantaneous contacts and 0 normally-closed contacts, with a leading contact count of 0 and lagging switching count of 0. The auxiliary and control circuit connection uses ring terminal lugs, which give a vibration-resistant termination compared to spring-cage or screw-clamp on smaller contactors. The block measures 36 mm wide, 37.5 mm high, and 43.7 mm deep — the depth is the dimension that projects forward from the contactor face, so check clearance to the enclosure door or adjacent devices.
The front face is rated IP00 (no protection against dust or water ingress), so the switch block must be mounted inside a closed panel or enclosure. Surge voltage resistance is 6 kV, and the mirror contact function per IEC 60947-4-1 is achieved when used with the 3RT2 contactor — this is relevant for safety-related feedback circuits where the N/C mirror contact must positively indicate the main contact position.