How to Install a Siemens SIRIUS Thermal Overload Relay

Pre-Installation Checks

1. Confirm the relay’s current range matches the motor’s full-load amperage (FLA) marked on the motor nameplate.
2. Prepare a matching Siemens SIRIUS contactor, insulated screwdriver and multimeter.
3. Inspect the relay housing and terminals for physical damage before assembly.

Step-by-Step Installation

1. Cut off power first: Shut down all upstream power supply to eliminate electric shock and equipment damage risks.
2. Assemble with the contactor: Align the relay with the contactor’s mounting base and DIN rail, then press firmly until it locks into place. The SIRIUS series adopts a direct plug-in design for easy assembly.
3. Wire the main circuit: Connect three-phase lines to the input and output terminals in the correct phase sequence, and tighten screws to the torque value marked on the product.
4. Wire the auxiliary circuit: Connect NO/NC auxiliary contacts to the alarm or control loop as required.

Key Settings After Wiring

• Current calibration: Turn the adjustment dial precisely to the motor’s rated current value.
• Trip class confirmation: Verify that the trip class (Class 10 / 20 / 30) matches the load’s startup characteristics.
• Reset mode selection: Choose manual or automatic reset mode according to on-site operation needs.

Post-Installation Verification

1. Use a multimeter to test continuity and insulation performance before powering on.
2. Run a no-load test to confirm the basic operation of the relay.
3. Check that the trip signal and auxiliary contact output work normally.