Schneider Electric LV429387 — Shunt Trip Compatibility Guide

By Abdullah Zahid
12 min read
Schneider Electric LV429387 MX shunt trip release mounted on ComPacT NSX circuit breaker, spring terminal connections visible

Schneider Electric LV429387 Shunt Trip Release MX, ComPacT NSX, 220/240VAC 50/60Hz, 208/277VAC 60Hz, Screwless Spring Terminal Connections — Specs, Compatibility and Selection Guide

If you are specifying or replacing a remote trip accessory for a ComPacT NSX, PowerPact Multistandard, or EasyPact CVS circuit breaker on an AC control circuit, the Schneider Electric LV429387 is the part that belongs on your bill of materials. This MX shunt trip release is a voltage-operated auxiliary device that mechanically opens a molded case circuit breaker when a control signal is applied — covering control voltage inputs of 220–240VAC 50/60Hz or 208–277VAC 60Hz, with a 50 ms trip response time and screwless spring terminal connections rated for 0.5–1.5 mm² conductors. The critical pre-purchase question is straightforward: does your control circuit supply AC voltage in one of those two ranges, and is your breaker confirmed to be in the NSX, PowerPact, or EasyPact family? If yes to both, this is the correct part. If either answer is uncertain, read this guide before committing.

If you have already confirmed this is the right part, check current pricing and availability for the Schneider Electric LV429387 at LeadTime.ca — ships worldwide.

Who Should Buy the Schneider Electric LV429387 — and Who Should Not

The LV429387 is the right choice for engineers and panel builders who meet all of the following criteria:

  • Your circuit breaker is confirmed as ComPacT NSX (100–630 A), PowerPact Multistandard, or EasyPact CVS — not a different brand or family
  • Your control circuit delivers 220–240VAC 50/60Hz or 208–277VAC 60Hz at the breaker mounting location, measured on-site with a multimeter, not assumed from a transformer nameplate
  • Your wiring uses conductors in the 0.5–1.5 mm² (AWG 20–16) range, compatible with spring terminal termination
  • Your control signal is either a maintained voltage hold or an impulse of at least 20 ms duration — shorter pulses will not reliably trip the breaker
  • Your application requires a shunt trip (opens on voltage rise above 70% of rated voltage), not an undervoltage release that opens on voltage drop
  • Your project demands IEC 60947-2, UL, and CSA certified auxiliary releases without additional qualification testing

If your control circuit is 24VDC, 48VDC, or any DC voltage, the LV429387 is not suitable — it is an AC-only device. If your breaker is from a different manufacturer, this accessory will not physically mount or electrically interface. In those cases, contact the LeadTime.ca team to identify the correct release for your application before ordering.

On this page:

What the Schneider Electric LV429387 Actually Does in Your System

The LV429387 is a shunt trip release — catalogued under Schneider Electric's MX voltage release designation — that adds remote and automated opening capability to ComPacT NSX, PowerPact Multistandard, and EasyPact CVS molded case circuit breakers. Without this accessory, a circuit breaker can only be opened manually at the panel. With the LV429387 installed, an external control signal applied to the shunt trip terminals commands the breaker to open within 50 ms, cutting power to the downstream load from any remote location that can deliver the control voltage.

The operating principle is voltage-based: when the control circuit voltage rises above 70% of the rated control voltage (Un), the MX coil energizes and mechanically releases the breaker latch, tripping it to the open position. The operating window extends up to 110% of rated voltage, which means normal facility voltage fluctuations within that band will not cause nuisance tripping. The signal can be either a maintained voltage hold — where the control voltage is held continuously during the trip demand — or an impulse of at least 20 ms duration. Pulses shorter than 20 ms will not deliver sufficient energy to the coil to complete a reliable trip, which is a common source of field failure when control logic has not been validated against this specification.

The practical applications are direct: emergency stop circuits where a safety relay must de-energize a load instantly, remote panel shutdown from a control room, machine safety interlocks that respond to sensor-detected hazard conditions, UPS switchover automation that opens the main breaker before transferring to backup supply, and scheduled load shedding commanded by an energy management system. In each case, the LV429387 eliminates the need for personnel to physically access the panel, which is both a safety and an operational efficiency advantage. The spring terminal design — rated for 0.5–1.5 mm² conductors with a 7 mm strip length — reduces wiring assembly time compared to legacy screw terminal models, with an estimated 40% reduction in wiring time documented by Schneider Electric for panel builders.

Where the LV429387 Sits in a Typical Control System

The LV429387 mounts on the face of the circuit breaker at the auxiliary post, sitting between the control circuit signal source and the breaker's mechanical trip mechanism. It does not carry load current — its sole function is to receive the control voltage and convert it into a mechanical trip action.

  • Control voltage source (control transformer, UPS output, or safety relay power supply delivering 220–240VAC or 208–277VAC 60Hz) feeds the shunt trip terminals
  • Safety relay, pushbutton, or automated controller closes the control circuit contact, sending voltage to the LV429387 coil
  • LV429387 coil energizes above 70% of rated voltage and mechanically releases the ComPacT NSX, PowerPact, or EasyPact CVS breaker latch
  • Circuit breaker opens within 50 ms, interrupting all load current to downstream equipment
  • Downstream load (motor, distribution panel, HVAC equipment, or production machinery) is de-energized; breaker remains open until manually reset

Typical Applications for the LV429387 MX Shunt Trip

Emergency stop systems are the most common deployment scenario. A safety relay connected to an operator mushroom button or a light curtain sends a maintained voltage signal to the LV429387, tripping the upstream breaker and de-energizing the machine within 50 ms of the hazard detection. This is a well-established application in manufacturing, packaging, and process control environments where IEC 60947-2 compliance is required by the safety specification.

Remote panel shutdown is a frequent requirement in data centers, telecommunications rooms, and large commercial facilities where the breaker panel is physically inaccessible or in a restricted zone. The LV429387 allows a facility operator at a central control desk to open a specific branch circuit breaker without entering the electrical room, which is both operationally convenient and a safety improvement over manual intervention.

UPS and backup power transfer applications use the shunt trip to coordinate breaker state during utility loss events. The transfer logic detects incoming voltage loss, commands the LV429387 to open the main breaker, and closes the alternate supply path — all within the timing window that the UPS or generator transfer logic requires.

Machine safety interlocks in OEM equipment — particularly in petrochemical, food processing, and industrial automation — connect the LV429387 to sensor outputs that detect over-temperature, over-pressure, or equipment fault conditions, providing a hardware-level shutdown path that does not depend on software or PLC execution cycles.

Scheduled load shedding for energy management systems uses the LV429387 to remotely open non-critical circuit breakers during peak demand periods, with the command issued by a building automation controller over the control circuit.

Application Typical Deployment
Emergency stop circuit Safety relay output → LV429387 → ComPacT NSX trips load within 50 ms on operator or sensor signal
Remote panel shutdown Control room pushbutton → control circuit → LV429387 opens breaker in restricted electrical room
UPS switchover automation Transfer controller closes shunt trip circuit on utility loss; breaker opens before backup supply energizes
Machine safety interlock Over-temperature or fault sensor → safety relay → LV429387 trips NSX to stop OEM equipment
Scheduled load shedding Building automation controller commands shunt trip via timed relay output during peak demand window

LV429387 Key Specifications and Variant Comparison

Parameter Value Notes
Control Voltage Option 1 220–240VAC, 50/60Hz Standard for North American commercial panels and IEC 50Hz regions
Control Voltage Option 2 208–277VAC, 60Hz US industrial standard; 50Hz not available for this voltage class
Operating Threshold 0.7–1.1 × Un (70–110% rated voltage) Coil energizes above 70%; holds to 110% without nuisance trip
Response Time 50 ms Coil energization to full breaker open; meets IEC 60947-2 timing
Signal Type Impulse (≥20 ms) or Maintained Pulses below 20 ms will not reliably trip the breaker
Supply Inrush Power 10 VA Verify control circuit supply capacity before installation
Terminal Type Spring terminals (screwless) Estimated 40% wiring time reduction vs. screw terminals
Wire Gauge Compatibility 0.5–1.5 mm² (AWG 20–16) Wire stripping length: exactly 7 mm
Frame Size Compatibility NSX 100/160/250/400/630 A Also PowerPact Multistandard and EasyPact CVS; confirm nameplate
Certifications IEC 60947-2, UL Listed, CSA Certified No additional qualification testing required for North American codes

Full technical specifications are available on the product page at LeadTime.ca.

Control Voltage Input Region / Standard Compatible with LV429387 Notes
220–240VAC 50/60Hz IEC Europe, 50Hz global, North American 240V supplies Yes Standard selection for most legacy North American and international panels
208–277VAC 60Hz North American 208V delta/wye, 277V three-phase Yes Common US industrial and commercial; 50Hz not available at this voltage
24VDC North American low-voltage controls No Requires alternative release family; LV429387 is AC-only
12VDC / 48VDC Renewable energy, backup power No DC-capable variant or different product family required
120VAC North American single-phase branch circuits No Below operating threshold; coil will not energize reliably

If your control circuit falls outside the 220–240VAC or 208–277VAC 60Hz bands, the LV429387 is not the correct selection — check the product page for alternative part numbers or contact the LeadTime.ca team to identify the correct release for your voltage class.

Expert Verdict: Is the LV429387 the Right Shunt Trip for Your Project?

The Schneider Electric LV429387 is the correct and logical choice for electrical engineers, panel builders, and OEM integrators who are already standardized on the ComPacT NSX, PowerPact Multistandard, or EasyPact CVS breaker families and are operating AC control circuits in the 208–277VAC or 220–240VAC range. Its IEC 60947-2 compliance combined with UL Listed and CSA Certified marks means buyers in Canada, the United States, and internationally do not need to run additional qualification testing before commissioning — the certification work is already done. The 50 ms trip response satisfies the timing requirements of most emergency stop and safety interlock standards, and the spring terminal design delivers a measurable labor reduction of approximately 40% in assembly time for high-volume panel builds, making it particularly well-suited for OEMs producing more than a handful of panels per year.

Where the LV429387 has genuine limits, buyers should be direct with themselves before ordering. This accessory does not work with DC control circuits — not at 24VDC, 48VDC, or any other DC voltage. If your safety circuit or building automation system delivers a DC control signal, the LV429387 will not function and a different release family is required. Additionally, if your application demands a sub-40 ms trip time, you will need to verify carefully whether 50 ms satisfies the safety interlock timing budget in your specific safety standard before committing. For projects where the breaker family is not confirmed as NSX, PowerPact, or EasyPact CVS — including any non-Schneider breaker — this accessory will not physically mount and should not be ordered. In retrofit scenarios where the breaker generation or frame size is unknown, the safest approach is to photograph the breaker nameplate and confirm compatibility before the purchase order is placed.

From a procurement standpoint, the LV429387 is listed as non-stock at the manufacturer's direct channel, which means lead times through generic resellers can be unpredictable. Sourcing through a specialist distributor gives you upfront stock confirmation, compatibility verification before shipment, and access to application support if wiring or commissioning questions arise on-site — all of which reduce the risk of a project delay caused by a wrong part or a mis-wired installation. Check current availability and pricing for the LV429387 at LeadTime.ca — the team ships worldwide and can advise on lead time before you commit to a project schedule.

For volume pricing or to confirm lead time before committing to a build, contact the LeadTime.ca team directly — we ship worldwide.

What Engineers Need to Know Before Ordering the LV429387

Because community forum data for the Schneider Electric LV429387 is sparse, the most reliable source of pre-purchase intelligence for this part is the body of engineering knowledge that has accumulated around its most common failure modes and ordering errors. The pattern is consistent: the LV429387 is a well-specified and straightforward product, but the installation context surrounding it — control voltage, signal timing, terminal preparation, and breaker family confirmation — generates the vast majority of field problems. Understanding these risks before the purchase order is placed is the single most effective way to avoid a costly rework cycle.

The most frequently encountered issue in the field is a control circuit voltage mismatch. Engineers sometimes specify the LV429387 based on the control transformer nameplate rather than measuring the actual voltage at the breaker mounting location. Voltage drop across long cable runs, transformer regulation, or parallel loads can bring the available voltage below the 70% threshold required to energize the coil. The coil sees insufficient voltage, the breaker does not trip, and the field team reports a defective unit — when the actual cause is a voltage that never reached operating threshold. Measuring at the exact terminal location with a multimeter, not at the transformer output, eliminates this failure mode entirely.

The second consistent source of ordering errors is AC versus DC control voltage. The LV429387 is an AC-only shunt trip. Engineers specifying a shunt trip for a system that uses 24VDC control logic — which is the most common low-voltage control standard in modern industrial automation — will receive a part that cannot function in their application. The MN variant or an alternative release family is required for DC control. If you are uncertain which release applies to your control architecture, the LeadTime.ca team can help you identify the correct Schneider Electric part before you commit to an order, which is far less expensive than returning and re-specifying after the panel build has begun. The Wrong-Part Prevention Checklist below captures the full set of pre-order verifications that prevent these errors.

Wiring and Installation Overview

The following points cover the key requirements for mounting and connecting the LV429387. For full installation procedures, refer to Schneider Electric's official product documentation for the ComPacT NSX auxiliary device installation guide.

  • The LV429387 mounts face-on to the circuit breaker at the auxiliary post; only one MX or one MN release can be installed per breaker — not both simultaneously
  • Strip exactly 7 mm of insulation from each control conductor before insertion into the spring terminals; under-stripping causes intermittent contact and nuisance trips, over-stripping exposes bare conductor that can contact adjacent terminals
  • Control conductors must be within the 0.5–1.5 mm² (AWG 20–16) range; conductors outside this range require crimp ferrules or adapter sleeves before spring terminal insertion
  • Verify control circuit inrush capacity can supply 10 VA during coil energization; undersized control transformers may see voltage sag that prevents reliable trip
  • Before energizing the main load, apply control voltage and verify the trip signal causes the breaker to open within 50 ms; confirm the breaker handle is in the full open position and document the test result for compliance records

Compatible Breaker Families and Accessory Expansion

The LV429387 is certified for use within Schneider Electric's own circuit breaker ecosystem. Compatibility is confirmed for the following families and frame sizes:

  • ComPacT NSX — Legacy generation (pre-2010): 100, 160, 250, 400, 630 A frames; full compatibility with spring terminal LV429387
  • ComPacT NSX — New generation (2010 onward): same frame range; confirm breaker year on nameplate for new-generation physical fitment
  • ComPacT NSX DC variant: 100–630 A frames; note that the LV429387 control circuit is AC-only — the DC designation refers to the breaker's load-side DC interrupting capacity, not the control circuit voltage; confirm your control supply is still AC
  • PowerPact Multistandard: all generations, 250–1600 A frames; confirm auxiliary post presence on specific frame before ordering
  • EasyPact CVS: all versions, 30–160 A compact frames; MX release fits the standard auxiliary mount on this series
  • Other brands (Eaton, ABB, Siemens, GE, older Square D I-line): not compatible — brand-specific mounting and coil interfaces are not interchangeable; sourcing the equivalent release from the correct manufacturer is the only valid path

Wrong-Part Prevention Checklist

Before placing an order for the Schneider Electric LV429387, confirm each of the following items in sequence. These are verbatim from the manufacturer and distributor technical guidance — do not skip any step:

  1. Verify your circuit breaker model: Is it ComPacT NSX, PowerPact Multistandard, or EasyPact CVS? (Check nameplate.) If different brand/series, stop — LV429387 will not fit.
  2. Verify control circuit voltage: Will your control signal come from 220–240VAC 50/60Hz OR 208–277VAC 60Hz? (Check control transformer or UPS output.) Single-phase AC only; this unit does not work with DC.
  3. Verify frame size compatibility: Is your breaker rated 100, 160, 250, 400, or 630 amperes? Oversized frames may not physically mount the MX auxiliary.
  4. Verify terminal compatibility: Does your wiring bundle allow 0.5–1.5 mm² spring terminals? If existing panel uses larger gauge,

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