Schneider Electric LRD4369 TeSys Thermal Overload Relay 110-140 A

Overview

The Schneider Electric LRD4369 is a TeSys Deca (TeSys LRD) differential thermal overload relay with a current adjustment range of 110 to 140 A and trip class 10A according to IEC 60947-4-1. It is designed to protect three-phase motors against sustained overload and phase failure, and it is listed by Schneider Electric as compatible with the LC1D150 contactor. With lug clamp power terminals, a 1 NO + 1 NC auxiliary contact block, stop and reset push-buttons and ambient temperature compensation from −20 to 60 °C, it is the natural choice for large motor starters built around the TeSys D LC1D150 contactor.

Seven Star LLC supplies the Schneider Electric LRD4369 to panel builders, electrical contractors and maintenance teams in the Sultanate of Oman and the wider GCC. With engineering support in Muscat, we help customers confirm the setting range, contactor pairing and mounting accessories so that replacement relays fit existing MCC buckets without modification.

Operating Principle

A thermal overload relay models the heating of a motor winding. In the Schneider Electric LRD4369, the motor current flows through heater elements that warm bimetal strips in each phase. When current stays above the set value for long enough, the bimetals deflect far enough to operate a trip mechanism that opens the NC auxiliary contact, which in turn de-energises the contactor coil and disconnects the motor. Schneider Electric specifies a tripping threshold of 1.14 ±0.06 Ir, where Ir is the current setting on the dial, in line with IEC 60947-4-1. Class 10A defines the time-current characteristic: as general engineering guidance, a class 10A relay trips within a defined time at multiples of the setting, which suits standard motors with normal starting times.

The word differential in the product description refers to the phase-failure sensitivity built into the mechanism. If one phase is lost on a motor protected by the Schneider Electric LRD4369, the remaining phases carry more current and the bimetals deflect unevenly; the differential mechanism detects this imbalance and trips faster than a simple overload would. The Schneider Electric LRD4369 datasheet gives the phase-failure tripping current as 130 % of Ir on two phases with the third at zero. Ambient temperature compensation from −20 to 60 °C prevents the relay from tripping early in hot switch rooms, a practical point for panels in Oman during the summer months.

Engineering Design of the Schneider Electric LRD4369

Physically, the Schneider Electric LRD4369 is a block-type relay that mounts directly under the contactor, or on a plate or rail with specific accessories. The power circuit uses screw clamp terminals that accept one cable of 4 to 50 mm² solid or flexible without cable end, or 4 to 35 mm² flexible with cable end, tightened to 9 N·m. The control circuit terminals accept two cables of 1 to 2.5 mm² and are tightened to 1.7 N·m. The relay has a depth of 132 mm and a net weight of 0.9 kg, with IP20 protection according to IEC 60529.

The front face of the Schneider Electric LRD4369 carries the current adjustment dial, a red stop push-button and a blue reset push-button. The auxiliary contacts are rated with a conventional free-air thermal current of 5 A for signalling circuits, 0.12 A at 600 V AC-15 and 0.06 A at 440 V DC-13, and should be protected by a 4 A gG or BS fuse. The power circuit has a rated insulation voltage and rated operational voltage of 1000 V, a rated impulse withstand voltage of 6 kV and operates over a network frequency of 0 to 400 Hz, on both AC and DC networks.

Key Features

The Schneider Electric LRD4369 offers the following features for motor starter design and maintenance.

• Thermal protection adjustment range of 110 to 140 A for large motor starters.
• Trip class 10A according to IEC 60947-4-1, suited to standard motor starting duty.
• Differential mechanism with phase-failure sensitivity at 130 % of Ir on two phases.
• Ambient temperature compensation from −20 to 60 °C.
• Integrated 1 NO + 1 NC auxiliary contacts for contactor control and alarm signalling.
• Red stop and blue reset push-buttons on the front face.
• Direct mounting under the LC1D150 contactor, or separate mounting with specific accessories.
• Lug clamp power terminals for cables up to 50 mm², with ATEX INERIS listed among product certifications.

Industrial Applications

In the GCC the Schneider Electric LRD4369 is used wherever large low-voltage motors are started direct-on-line or star-delta through TeSys D contactors: chilled-water and condenser pumps in district cooling plants, seawater intake and transfer pumps at desalination plants in Oman, compressors, cooling-tower fans, process pumps in oil and gas facilities and conveyor drives in cement and mining operations. Building services contractors use it in MCCs for HVAC and firefighting pump sets, and OEM skid builders in the Sohar and Salalah free zones specify it for packaged equipment exported across the region. The datasheet lists ATEX INERIS among product certifications; as general guidance, the relay itself is installed in a safe-area panel and the certification relates to protecting motors located in hazardous areas.

For lower currents, Seven Star LLC also supplies the Schneider Electric TeSys LRD thermal overload relay family for smaller contactors, the Schneider Electric TeSys LR9F electronic overload relay for applications that need wider setting ranges or selectable trip classes, and alternatives such as the ABB TA25DU6.5 thermal overload relay. Our team in Muscat can help select the right device for new panels and replacements across Oman and the GCC.

Schneider Electric LRD4369 Technical Specifications

The data below for the Schneider Electric LRD4369 is taken from the Schneider Electric product data sheet for LRD4369.

Setting and Replacement Notes for the Schneider Electric LRD4369

As general practice, the dial of a thermal overload relay is set to the full-load current shown on the motor nameplate, adjusted where required for service factor according to the applicable code and the motor manufacturer’s guidance. When replacing an older relay in an existing starter, check that the contactor is an LC1D150 or another model listed as compatible, confirm the lug clamp connection and cable size, and verify that the auxiliary contacts are wired into the contactor coil circuit before the starter is energised.

How to Order

To request a formal quotation for the Schneider Electric LRD4369, send the quantity and the contactor model in your starter to the Seven Star LLC electrical team. We provide engineering support in Muscat, can share the manufacturer data sheet for your submittal, and supply motor control components to projects throughout Oman and the GCC.