What this part is
The Siemens 3RT1936-4NB00 is an adapter plate designed to retrofit older 3TF46 through 3TF49 contactors onto a SIRIUS 3RT mounting rail. It is a mechanical conversion piece, not a standalone contactor — it lets you swap in a newer SIRIUS 3RT2 contactor without re-drilling the panel or changing the backplate layout. The lifecycle stage is listed as current, meaning it remains an active catalog line for this retrofit application.
What it replaces
This adapter plate specifically targets the 3TF46, 3TF47, 3TF48, and 3TF49 contactor sizes, providing the mounting geometry and terminal spacing to accept a SIRIUS 3RT2 contactor in their place. It is a pure mechanical adapter — no electrical function, no coil, no auxiliary contacts. If your BOM calls for a 3TF-series contactor and you want to migrate to the 3RT2 platform, this plate is the bridge. For a direct drop-in without the adapter, the 3RT2016-1DF47 is a SIRIUS contactor of size S00 with screw terminals, but it is a different form factor and will not bolt into a 3TF46-49 footprint without this plate.
Panel integration note
The adapter plate mounts onto the existing DIN rail or screw-pattern used by the 3TF46-49 contactors. The SIRIUS 3RT2 contactor then snaps onto the plate. This avoids re-drilling the backplate or re-routing the main power wiring if the busbar positions align. Verify the 3RT2 contactor's terminal spacing against your existing busbar layout before ordering — the plate adapts the mounting footprint, not the electrical connection pitch.