Bitzer SE-G4

What does Bitzer SE-G4 mean?

The SE-G4 is a BITZER compressor protection device that monitors motor winding, discharge-gas and oil temperature and locks out immediately when a preset limit is exceeded. It also monitors rotation direction, phase sequence and phase failure, and detects broken or shorted sensor leads. It is suitable for soft-starter operation with a run-up time up to 2 seconds and replaces the SE-G1. It is not suitable for screw compressors.

Symptoms

• Compressor stopped on over-temperature or a phase fault
• Immediate lockout if rotation direction is wrong after start
• Safety chain opens then recloses about 6 minutes later
• Permanent lockout after repeated phase failures

Common causes

• Winding, discharge-gas or oil temperature over the limit
• Wrong rotation direction detected 6-10 seconds after start
• Single or repeated phase failure on the supply
• Broken or shorted temperature-sensor cable

Diagnostic steps

1. 01

   Identify the trip cause

   Determine whether temperature, rotation direction or phase failure locked the device; it stays locked until corrected.

2. 02

   Check rotation and phases

   Confirm correct phase sequence; the SE-G4 checks rotation from the 6th to 10th second after start and on wrong direction locks immediately.

3. 03

   Investigate phase failures

   Note that 3 phase failures within 18 minutes or 10 within 24 hours cause a permanent lockout; trace the dropped phase.

4. 04

   Address thermal and sensor faults

   If thermal, allow cooldown; check the sensor cable for breaks or shorts.

5. 05

   Unlock the device

   After fixing the fault, interrupt the supply voltage for at least five seconds, then restore power to clear the lockout.

When to call a professional

Only trained, authorized specialists may work on the compressor and system. Phase-rotation, phase-failure and soft-starter faults involve live electrical work for a qualified technician. Note the SE-G4 is not for screw compressors; confirming the correct device and diagnosing recurrent lockouts should be left to a refrigeration professional.