GE Multilin SR469-CASE Drawout Relay Chassis Case Assembly

Description

Product Introduction

The GE Multilin SR469-CASE is the dedicated panel-mount drawout chassis engineered specifically for the GE Multilin 469 Motor Protection Relay system. Designed for medium-voltage motor control centers (MCCs) and switchgear doors, this rugged metal enclosure houses the slide-in 469 relay unit, allowing fast maintenance swaps without disconnecting panel field wiring.

Unlike standard fixed-mount electrical enclosures, the SR469-CASE incorporates heavy-duty backplane terminal blocks featuring spring-loaded, automatic Current Transformer (CT) shorting mechanisms. When the internal 469 relay unit is drawn out for testing or replacement, the case automatically shorts the CT secondary circuits, preventing hazardous open-circuit high voltages across the switchgear terminals.

Key Technical Specifications

Application Scenarios & The “Trench” Experience

It was during an emergency overhaul at a water treatment plant when a maintenance technician accidentally stripped the rear terminal block threads on a 469 motor protection relay case while re-torquing CT wires. The main 1,500 HP raw water pump couldn’t be re-energized with compromised CT contacts. With the entire pump house offline, finding a drop-in SR469-CASE to replace the damaged enclosure without re-drilling the switchgear door panel was the only option to get the pump running before municipal storage tanks drained.

• Medium-Voltage Motor Control Centers (MCCs) – Housing drawout protection units for large induction and synchronous motors.
• Refineries & Chemical Facilities – Enabling safe, live-swap maintenance of motor protection units in hazardous area control rooms.
• Mining & Heavy Processing Plants – Shielding relay backplane terminations against heavy vibration and coal/dust buildup.
• Power Plant Auxiliary Drives – Providing reliable, touch-safe relay isolation on boiler feed pumps and forced-draft fan drives.

Field Case Study

A paper mill scheduled a 12-hour turnaround to upgrade three older fixed-mount motor protection units to drawout Multilin 469 setups. They pre-wired three SR469-CASE enclosures onto the new breaker cubicle doors prior to shutdown day. When the outage started, the electricians landed the field wiring directly to the case terminal barrier blocks, racked in the 469 relay inner units, and completed secondary injection testing in half the allocated downtime window.

SR469-CASE

SR469-CASE

SR469-CASE

Transparency SOP: Quality Assurance & Testing

Case enclosures with CT shorting bars carry severe safety implications. We do not just glance at a metal box; we verify the mechanical and electrical integrity of every SR469-CASE.

1. Physical & Mechanical Inspection: Checking for metal warp, paint finish damage, bent mounting flanges, and latch engagement hardware.
2. Backplane Pin Alignment: Verifying that all female pin sockets and male connector tracks align cleanly without binding or tolerance slop.
3. CT Shorting Bar Verification: Testing mechanical spring tension and electrical continuity on all CT shorting contacts to ensure 100% reliable shorting action when the relay unit is removed.
4. Terminal Thread Audit: Checking every terminal screw thread on the rear barrier strips for stripping, cross-threading, or corrosion.
5. Cleanroom Blowout & ESD Prep: Cleaning all barrier insulation blocks and packing the chassis in heavy protective wrap with corner padding for transport.

The Veteran’s Tech Trap Guide (Crucial Value-Add)

• ⚠️ Never Force the Relay Unit In: When sliding a 469 relay into the SR469-CASE, it should seat smoothly. If you feel hard resistance before the drawout handle engages, STOP. A misaligned backplane pin or debris in the guide track will crush the rear connector block.
• ❗ Verify CT Shorting Bar Operation: Before wiring up live CT lines, manually insert and remove a dummy or test relay while measuring continuity across the case CT terminals. Confirm the shorting bars drop closed the instant the relay disconnects. An open CT secondary generates lethal kilovolt spikes!
• ⚠️ Torque Terminal Screws Properly: The rear barrier block screws require proper torque specs. Over-tightening will crack the phenolic terminal base or strip the brass inserts; under-tightening causes high-resistance hot spots under heavy motor load.
• ❗ Check Panel Gasket Sealing: When panel-mounting the case in dusty or washdown environments, verify the front perimeter gasket is intact and fully compressed against the door cutout to maintain the enclosure’s NEMA rating.

Frequently Asked Questions (FAQ for Conversion)

Q: Does the include the internal 469 relay unit?

A: No. The is the empty drawout chassis assembly (outer case and backplane terminal block). The internal 469 relay controller module is sold separately.

Q: Can I use this case for a Multilin 489 or 745 relay?

A: While some GE Multilin relays share similar physical chassis sizes (like the 489 Generator Protection Relay), terminal wiring pinouts vary. You must verify backplane terminal layout compatibility with your specific relay model code.

Q: What happens to my CT circuits when I pull the relay out of the ?

A: The contains built-in, spring-loaded shorting contacts. The moment the relay is withdrawn, the internal shorting bars automatically close across the CT terminals, keeping your field CT loop safely shorted.

Q: Is it safe to replace a damaged case while field wiring is connected?

A: No! You must completely de-energize all potential transformer (PT) inputs, auxiliary power feeds, and externally short/isolate all field CT secondaries before disconnecting wires to swap out a case.

Q: What warranty comes with this replacement case assembly?

A: We back all assemblies—whether factory-sealed new surplus or bench-verified refurbished units—with a complete 12-month replacement warranty.