Schneider Thermal Overload Relay LRD21

Schneider Electric LRD21 Thermal Relay

Schneider Thermal Overload Relay LRD21 — Dependable Motor Protection for Medium Loads

The Schneider Thermal Overload Relay LRD21 is a high-quality three-pole thermal protection device from the trusted Schneider Electric TeSys LRD range. Designed to protect medium-capacity three-phase motors, this relay delivers accurate and dependable overload safeguarding for industrial and commercial electrical systems — helping prevent motor damage, reduce downtime, and enhance overall system safety.

🔌 What Is the Schneider LRD21 Thermal Overload Relay?

The LRD21 is a three-pole thermal overload relay with an adjustable thermal setting range of 12 – 18 A. It continuously monitors current through all three phases and disconnects the motor circuit when prolonged overload, phase loss, or unbalanced conditions are detected, protecting the motor from overheating and insulation failure. Ideal for pairing with Schneider contactors such as LC1D18, LC1D25, LC1D32, and LC1D38, the LRD21 is a key part of robust motor starter assemblies.

🛠️ Key Features & Benefits

• Adjustable Current Range (12 – 18 A) — Allows precise configuration to match your motor’s full-load current for tailored protection.

• Three-Pole Thermal Monitoring — Monitors all three phases for overload, phase loss, and unbalance.

• Class 10A Trip Characteristic — Conforms to IEC standards for reliable tripping on sustained overloads while tolerating normal start-up currents.

• Phase Loss & Imbalance Detection — Enhances safety by tripping when abnormal current conditions occur.

• Auxiliary Contacts (1NO + 1NC) — Enables signalling to control panels or automation systems for fault indication.

• Manual/Automatic Reset & Test Function — Provides flexible reset behaviour and easy testing without powering down.

• Secure Screw-Clamp Terminals — Offers reliable, vibration-resistant connections for both power and control wiring.

• Direct & Panel Mounting Options — Compatible with mounting under contactors or separate DIN-rail/panel installation for flexible setups.

⚙️ Why Use the LRD21 Overload Relay?

Thermal overload relays like the LRD21 are essential in ensuring safe and reliable motor operations. By detecting excessive heat from prolonged overload or phase irregularities early, this relay helps:

• Prevent motor overheating and winding damage

• Reduce unplanned downtime and maintenance costs

• Improve electrical system safety and longevity

• Extend motor service life with dependable protection

• Integrate seamlessly with Schneider contactors for compact, efficient motor starters

Whether you’re building a new control panel or upgrading an existing system, the LRD21 delivers consistent and dependable motor protection.

📌 Typical Applications

The Schneider Thermal Overload Relay LRD21 is ideal for:

• Industrial motor starter assemblies

• Pumps, compressors & ventilators

• Conveyors and material handling equipment

• HVAC drives and fan motors

• Production machinery and automated systems

• Commercial and factory electrical panels

This versatility makes the LRD21 a trusted choice for engineers, electricians, and maintenance professionals managing three-phase motor systems.