The Siemens 3RV1938-1A is a SIRIUS disconnector module designed for Size S2 motor circuit breakers. It provides a visible isolating distance and can be locked in the disengaged position, giving a positive mechanical disconnect for safe maintenance access. The module measures 149 mm deep, 55 mm wide, and 57 mm high, fitting the standard S2 footprint on a DIN rail or mounting plate.
Lifecycle and Sourcing Reality
The 3RV1938-1A is a phased-out product. The official Siemens successor is the SIRIUS 3RV2 series, with the preferred replacement order code 3RV2938-1A. For existing panels or BOM lines that still call out the 3RV1938-1A, the part is sourced to order through independent distribution against an RFQ — availability and current pricing are confirmed at quote time.
What the Ratings Mean for Fit
The visible isolating distance means the module creates a physical air gap you can see when disengaged — a requirement for lockout/tagout on motor circuits. The lockable disengaged position lets you secure the disconnect with a padlock, meeting OSHA-style isolation needs. Size S2 tells you it mates with S2-frame Siemens breakers like the 3RV20 series; the 55 mm width matches the standard S2 module pitch, so it drops into the same DIN-rail slot as the breaker it serves. The -20 to +70 °C operating range covers most indoor panel environments, while the -50 to +80 °C storage range allows cold warehouse or hot shipping without damage.
Deployment Context
Mounts directly on a 35 mm DIN rail in the same footprint as the Size S2 motor circuit breaker. Use it upstream of the breaker as a service disconnect — the visible gap confirms the circuit is dead before you open the panel. The lockable handle accepts standard padlock hasps for group lockout procedures.