Schneider Electric LRD3365 TeSys 80-104 A Overload Relay

LRD3365 thermal overload relay for 80 to 104 A motors

The LRD3365 is a Schneider Electric product listed in the datasheet as: TeSys LRD thermal overload relays – 80 to 104 A – class 10A. In a motor starter it is the part that watches the current of the motor and opens the control circuit when an overload or a lost phase would otherwise overheat the windings. Seven Star LLC supplies the LRD3365 in Oman and the GCC as an independent supplier based in Muscat.

Reading the reference: the datasheet identifies the LRD3365 as part of the TeSys LRD family, and the title gives the figure that matters, namely the adjustable window of 80 to 104 A with thermal class 10A. It is built as the largest frame in this group (70 mm wide) used with LC1D80 and LC1D95 contactors. The 80 to 104 A range is the top of the LRD3 frame in this group and pairs with the LC1D80 and LC1D95 contactors. It suits large motors whose nameplate current lies between 80 and 104 A.

Technical specifications of the LRD3365

Contactors and mounting for the LRD3365

The datasheet lists the contactors compatible with the LRD3365 as LC1D80, LC1D95. The mounting options are plate, with specific accessories; rail, with specific accessories; under contactor. In practice the relay plugs straight under a TeSys Deca contactor of the listed frames, so the contactor and relay together form a compact direct-on-line or reversing starter without extra wiring in the power circuit.

The relay body measures 70 mm wide, 81 mm high and 115 mm deep and weighs 0.51 kg. It belongs to the largest frame in this group (70 mm wide) used with LC1D80 and LC1D95 contactors. The setting range climbs past 100 A, so the associated power cables, short-circuit protective device and contactor rating must all be checked together; the relay only protects against overload, not short circuits.

Where the LRD3365 is used in Oman and the GCC

The largest frame in this group is used for big utility motors, such as main cooling-water pumps and large ventilation or process fans, where the starter is a major item in the panel. In Oman and the GCC such starters appear in water and desalination plants, oil and gas auxiliaries, power station balance-of-plant and building services.

Heat and dust are the main enemies. Overload relays are temperature-compensated, but a hot, dusty panel still ages terminals and contacts faster, so inspect the connections of the LRD3365 during planned shutdowns and keep the front cover and dial clean.

How the LRD3365 reacts to overload

The setting dial of the LRD3365 covers 80 to 104 A. The datasheet gives the tripping threshold as 1.14 ± 0.06 Ir conforming to IEC 60947-4-1, which means the relay is built to trip when the motor current reaches about 1.14 times the dialled value, with a tolerance of 0.06 times. At the top of the scale, 1.14 times 104 A works out to about 118.56 A; at the bottom of the scale, 1.14 times 80 A is about 91.2 A.

The relay is also a differential type. For the phase failure case, the datasheet states a tripping current of 130 % of Ir on two phases while the third carries nothing, which at 104 A corresponds to about 135.2 A in the two live phases. This sensitivity is what protects a three-phase motor from running on two phases after a blown fuse or a loose terminal, and it is the reason the type is chosen over a simple thermal element for pumps and fans.

Class 10A is the common choice for motors that start quickly. Under IEC 60947-4-1 the class number is the longest tripping time in seconds at 7.2 times the setting current, so a class 10A relay reacts faster to a locked rotor than a class 20 relay. The relay has temperature compensation over -20 to 60 °C, so the setting does not drift within that band.

Before ordering the LRD3365

• Motor nameplate current: it must sit between 80 and 104 A, ideally in the middle of the dial.
• Contactor: the starter must use one of LC1D80, LC1D95.
• Trip class: this relay is class 10A; confirm that it suits the starting time of the load.
• Signalling circuit: the contact is rated 0.72 A at 500 V AC-15 for signalling circuit; 0.06 A at 440 V DC-13 for signalling circuit.
• Space: allow 70 mm x 81 mm x 115 mm and a weight of 0.51 kg.
• Status: say whether you need a spare for an existing starter or a new installation.

Neighbouring ranges around the LRD3365

The table below places the LRD3365 between its neighbours by current range, using the datasheet data of each reference. It helps when the nameplate current falls near a boundary or when the contactor decides the frame.

Testing and servicing the LRD3365

Set the dial of the LRD3365 to the nameplate current of the motor, not to the contactor rating. Press the red stop push-button to confirm that the contactor drops, then use the blue reset push-button to restore the relay. The relay should be checked after any short-circuit event, because a short-circuit protective device is still needed upstream; the overload relay does not replace it.

For spares, keep the same reference rather than guessing from the range, because the frame and the terminals differ between the compact, large and largest groups. If you need a relay for a different current, send us the contactor reference and the nameplate current and we will confirm the correct member of the family.

Information to send with an RFQ for the LRD3365

• Full reference LRD3365 and the quantity required
• Motor nameplate current, voltage and power
• Contactor reference the relay will be fitted to
• Required delivery location and timing
• Whether it is a spare, a replacement or a new installation

Documents and quotation

A datasheet for this product is attached on this page. It lists the electrical, mechanical and environmental data summarised above, and it is the document to check against your own drawings.

Send us the part number, quantity and application and we will confirm availability and a quotation. Seven Star LLC is an independent supplier in Muscat and is not affiliated with the manufacturer.