Thermal overload relay, TeSys Deca, 30-40A, class 10, box terminals LRD340

Motor protection in AC and DC networks - TeSys LRD340 bimetallic thermal overload relay

The LRD340 overload relay from the TeSys Deca family protects electric motors and AC circuits from the effects of overloads. It features a current setting range of 30…40 A and a 10A tripping class in accordance with the IEC 60947-4-1 standard - which means a tripping time of less than ten seconds at seven times the rated current. The device works directly with LC1D40A, LC1D50A, and LC1D65A contactors, mounted underneath it or next to it on a TH35 rail.

Protective functions

The relay performs four basic functions: overload (monitors load current), phase loss (detects the absence of one phase while others are energized, with a tripping threshold of approximately 130 % of the set current Ir), stalling or long start, and locked rotor overload. The device is temperature compensated in the range of −20…+60 °C, so the tripping characteristic does not change significantly due to ambient temperature.

The front panel features two buttons: red - stop / manual reset after tripping, and blue - switch between manual and automatic reset mode. After a fault, the signaling contact informs the control system of the fault state - useful for integration with PLC controllers.

Electrical connection

The power circuit uses EverLink BTR screw terminals, allowing for the connection of single-core or multi-core wires with a cross-section of 1…35 mm² without cable ferrules (tightening torque 5 N·m). The control circuit supports 1…2,5 mm² wires at a torque of 1,7 N·m.

Housing dimensions are 70 × 55 × 123 mm, weight 0,375 kg, protection rating IP20 - requires installation inside electrical enclosures.

Standards, certificates, and operating conditions

The device meets the requirements of EN/IEC 60947-4-1 and EN/IEC 60947-5-1, and holds UL 508, CSA C22.2 No 14 (North America), CCC (China), and EAC (Eurasian Economic Union) certificates. ATEX INERIS approval enables use in explosion-prone zones, and DNV-GL and LROS Lloyd's Register marine certificates allow for installation on ships and offshore platforms.

The rated insulation voltage is 690 V AC for the main circuit (600 V according to CSA/UL), and the impulse withstand voltage is 6 kV. Operating temperature −20…+60 °C without derating.

Environment and warranty

The product is labeled Green Premium: no substances covered by the RoHS directive above the declaration threshold, no mercury or toxic heavy metals, and no SVHC substances above the REACH limit. A Product Environmental Profile (PEP) and end-of-life instructions are available.

The manufacturer's warranty is 18 months.