The Schneider LV839239 is an MX 2nd opening voltage release for MasterPact MTZ drawout breakers — a control accessory that trips the breaker on loss or application of control voltage. It's the second MX coil position, meaning the breaker already carries one MX; this one adds a separate shunt-trip path for a second independent signal (e.g., remote emergency stop or undervoltage protection from a different source). Rated for 12 V DC control with a 50 ms response time across all three MTZ frame sizes. Holding power is 4.5 W / 4.5 VA, and the trip threshold sits at 0.7...1.1 Un.
Schneider has marked the LV839239 as Obsolete. That means factory production has ended — no new-build units are coming off the line. For a BOM that calls out this exact order code, the only channel is the independent surplus and last-time-buy market.
Drawout mounting means this coil is designed for the MasterPact MTZ drawout cradle — it plugs into the secondary disconnect block, not a fixed-mounted breaker. If your installation uses a fixed MTZ (non-drawout), this part won't physically connect. The 50 ms response is the time from voltage removal to contact opening; it's consistent across all three MTZ frame sizes, so the same coil works in an MTZ1 panelboard or an MTZ3 switchgear lineup. The 12 V DC control circuit is the coil's operating voltage — verify your control transformer or DC supply delivers 12 V DC nominal. The 0.7...1.1 Un threshold means the coil drops out (trips the breaker) when the control voltage falls below about 8.4 V DC, and it resets (re-energizes) above about 13.2 V DC. That's a standard undervoltage-release characteristic, not a shunt trip that fires on a pulse.