What this part is and what it does
The Siemens 3VA1110-1AA42-0CH0 is a SENTRON switch disconnector built in a molded-case circuit breaker (MCCB) form factor — IEC frame 160, 4-pole, rated 100 A continuous across the full operating temperature range from 40 °C to 70 °C. That means no derating curve to chase: it holds 100 A all the way up to 70 °C ambient, which is unusual for a disconnector in this footprint. It is a pure disconnect — no overload or short-circuit protection — so it goes into a circuit where the upstream breaker or fuse handles the fault clearing, and this part provides visible isolation for safe maintenance. The front terminals accept busbar connection, and the unit ships with a nut keeper kit for the main circuit connections. Panel builders will appreciate that the 70 mm depth and 101.6 mm width match the standard SENTRON 3VA1 family footprint — it drops into the same DIN-rail or screw-mount pattern as the breakers in the series.
Undervoltage release and auxiliary switch configuration
This variant includes an undervoltage release (UVR) coil rated 120-127 V AC, 50/60 Hz. When the control voltage drops below the dropout threshold, the UVR trips the disconnector open — standard practice for safety circuits where a loss of control power must isolate the load. The UVR does not have a leading contact, so the coil energizes simultaneously with the main contacts; plan the control wiring accordingly if you need the UVR to seal in before the main circuit closes. The auxiliary switch block carries two HQ (high-rupture-capacity) form-C contacts plus one HQ trip alarm switch — three CO contacts total. The trip alarm switch changes state only when the UVR or a manual trip opens the disconnector, giving the PLC a dedicated fault signal separate from the position-feedback aux contacts. That is a clean way to distinguish a deliberate open from a fault-induced open without extra logic in the controller.