What it is and where it fits
The Siemens 3VA9988-0AB22 is an electrical alarm switch accessory from the SENTRON family, designed as a changeover contact module type HQ for 3VA1 and 3VA2 molded-case circuit breakers. It mounts directly into the breaker accessory slot — no additional DIN-rail space consumed — and provides remote status indication via its changeover contacts.
Contact ratings — what the duty codes mean
Rated thermal current (Ith) is 6 A, which is the continuous carry capacity in free air. The switching capability depends on the load type and voltage. For AC resistive loads (AC-12), the contacts handle 6 A from 12 V up to 240 V. For AC inductive loads like contactor coils or small solenoid valves (AC-15), the rating drops to 3 A across the same voltage range — a derating that reflects the inrush current and arcing of inductive switching. On DC circuits, the ratings fall with voltage due to the sustained arc. At DC-12 (resistive), the switch carries 6 A at 12 V, 4 A at 24 V, and 2 A at 48 V. At DC-13 (inductive, e.g. DC contactors or relays), it manages 1 A at 12 V, 0.8 A at 24 V, and 0.4 A at 48 V. At higher DC voltages — 110 V and 250 V — the DC-13 rating drops to 0.2 A and 0.1 A respectively. These are the limits for reliable contact life; exceeding them accelerates pitting or welding.
Integration and physical fit
The module is 7 mm wide, 56 mm tall, and 30 mm deep — a single-pole-width footprint that clips into the 3VA breaker's accessory bay. Stripped length for wiring is 15 mm (0.6 in). Overvoltage category III and pollution degree 3 mean it's rated for the fixed-installation environment inside a panel, not for clean-room or conditioned spaces.