Schneider Electric LRD22L TeSys Deca 17-24 A Class 20 Relay

LRD22L: 17 to 24 A class 20 overload relay in plain terms

The LRD22L is a Schneider Electric product listed in the datasheet as: Thermal overload relay, TeSys Deca, 690VAC, 17 to 24A, 1NO+1NC, class 20, for D25 to D38, screw clamp. 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 LRD22L in Oman and the GCC as an independent supplier based in Muscat.

Reading the reference: the datasheet identifies the LRD22L as part of the TeSys LRD family, and the title gives the figure that matters, namely the adjustable window of 17 to 24 A with thermal class 20. It is built as the compact frame (45 mm wide) used with LC1D09 to LC1D38 contactors. This is the one class 20 relay in this group. The longer trip class lets motors with heavy or slow-starting loads, such as large fans with high inertia, crushers, centrifuges and long conveyors, accelerate without tripping on the start current, while still protecting the windings.

Technical specifications of the LRD22L

How the LRD22L reacts to overload

The setting dial of the LRD22L covers 17 to 24 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 24 A works out to about 27.36 A; at the bottom of the scale, 1.14 times 17 A is about 19.38 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 24 A corresponds to about 31.2 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 20 allows a longer tripping time than class 10A. 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 20 relay can ride through a slow, heavy start that a class 10A relay might cut short. The relay has temperature compensation over -20 to 60 °C, so the setting does not drift within that band.

Contactors and mounting for the LRD22L

The datasheet lists the contactors compatible with the LRD22L as LC1D25, LC1D32, LC1D38. 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 45 mm wide, 66 mm high and 76 mm deep and weighs 0.144 kg. It belongs to the compact frame (45 mm wide) used with LC1D09 to LC1D38 contactors. Class 20 gives more time on an overload than class 10A, so use it deliberately: the motor and cable must be able to tolerate the longer overload window. Do not swap class 10A for class 20 just to avoid nuisance trips without finding the cause.

Wiring the LRD22L: terminals and aux contact

On the power side the datasheet lists screw clamp terminals 1 cable 1.5 to 10 mm² flexible without cable end; screw clamp terminals 1 cable 1 to 6 mm² flexible with cable end; screw clamp terminals 1 cable 1.5 to 10 mm² solid without cable end. The tightening torque is listed as control circuit: 1.7 N.m – on screw clamp terminals; power circuit: 2.5 N.m – on screw clamp terminals. Use a torque screwdriver, because terminals on motor starters loosen over time with heat cycling and vibration.

The control side is a pair of contacts, described as 1 NO + 1 NC, with terminal marking 95 and 96 for the normally closed contact and 97 and 98 for the normally open contact. The permissible current of that signalling circuit is 3 A at 120 V AC-15 for signalling circuit; 0.22 A at 125 V DC-13 for signalling circuit, and the associated protection is 4 A gG for signalling circuit; 4 A BS for signalling circuit. Wire the normally closed contact in series with the contactor coil so that a trip drops the contactor, and use the normally open contact for a fault lamp or a PLC input.

Selection checklist for the LRD22L

• Motor nameplate current: it must sit between 17 and 24 A, ideally in the middle of the dial.
• Contactor: the starter must use one of LC1D25, LC1D32, LC1D38.
• Trip class: this relay is class 20; confirm that it suits the starting time of the load.
• Signalling circuit: the contact is rated 3 A at 120 V AC-15 for signalling circuit; 0.22 A at 125 V DC-13 for signalling circuit.
• Space: allow 45 mm x 66 mm x 76 mm and a weight of 0.144 kg.
• Status: say whether you need a spare for an existing starter or a new installation.

Where the LRD22L is used in Oman and the GCC

The compact frame is the workhorse of small motor control centres, local starter panels and skid-mounted packages, where many identical starters sit side by side and panel space is tight. 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 LRD22L during planned shutdowns and keep the front cover and dial clean.

Environment, approvals and standards for the LRD22L

The datasheet gives an operating ambient temperature of -20 to 60 °C without derating conforming to IEC 60947-4-1 and a storage range of -60 to 70 °C, with IP20 protection and V1 flame retardance. It states mechanical robustness as Shocks: 15 Gn for 11 ms conforming to IEC 60068-2-7; Vibrations: 3 GN conforming to IEC 60068-2-6. On sites in Oman the actual panel temperature in summer can be well above the outdoor mean when panels are in the sun, so compare your measured cabinet temperature with the datasheet limit and add ventilation or shading where needed.

Certifications listed for the LRD22L are IEC; UL; CSA; EAC; ABS; ATEX INERIS; UKCA. The standards named are EN/IEC 60947-4-1; EN/IEC 60947-5-1; UL 60947-4-1; UL 60947-5-1; CSA C22.2 No 60947-4-1; CSA C22.2 No 60947-5-1; EN 50495. Only rely on a certificate that is listed here for this exact reference; if a project needs a particular marine or hazardous-area approval, tell us and we will check it against the datasheet before quoting.

Information to send with an RFQ for the LRD22L

• Full reference LRD22L 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.