Schneider LT3SA00M | Thermistor protection units, TeSys LT3, 250VAC 50/60Hz, 115/230VAC 50/60Hz, 1NO+1NC, automatic reset

Schneider LT3SA00M | Thermistor Protection Unit, TeSys LT3, Automatic Reset

The Schneider LT3SA00M is a thermistor protection relay from the TeSys LT3 series, specifically designed to safeguard motors against overheating. It monitors the resistance of PTC thermistors embedded in motor windings and trips when the temperature exceeds a critical level. This model includes automatic reset, allowing quick reactivation once safe temperature conditions return.

General Overview:

• Brand: Schneider Electric

• Series: TeSys LT3

• Model: LT3SA00M

• Function: Thermistor protection unit (overtemperature protection)

• Reset Mode: Automatic

• Output Contacts: 1 NO + 1 NC

• Power Supply:

  • 250 V AC (50/60 Hz)

  • 115/230 V AC (50/60 Hz), switch-selectable

Key Features:

• PTC Thermistor Monitoring: Interfaces directly with PTC sensors inside the motor

• Automatic Reset: Relay automatically resets after the motor cools down

• Fail-Safe Operation: Detects open circuit and short circuit conditions in sensor wiring

• DIN Rail Mountable: For quick and easy installation in panels

• Status Indicators: LED for status monitoring (trip, operation)

• Compact Design: Fits in small control enclosures

Technical Specifications:

• Supply Voltage: 115/230 V AC or 250 V AC ±10%, 50/60 Hz

• Thermistor Resistance Range:

  • Trip Resistance: ≥ 3.3 kΩ

  • Reset Resistance: ≤ 1.5 kΩ

• Output Relay:

  • Contact Type: 1 NO + 1 NC

  • Rated Current: 5 A at 250 V AC

• Reset Type: Automatic only (no manual override on this model)

• Mounting Type: DIN rail

• Protection Rating: IP20 (housing), IP40 (front panel)

• Operating Temperature: -20°C to +60°C

• Standards: IEC 60947-8

Typical Applications:

• Motors equipped with PTC thermistors

• HVAC systems

• Pumps and compressors

• Fans, blowers, and conveyors

• High-duty cycle or frequently cycled motors

• Applications where thermal overload relays alone are insufficient

Benefits:

• Enhanced Motor Protection: Stops overheating before serious damage occurs

• Quick Auto Reset: Reduces downtime and eliminates the need for manual intervention

• Easy Integration: Compatible with most Schneider and third-party systems

• Compact & Durable: Saves space in panels while providing reliable protection