Bitzer SE-B3

What does Bitzer SE-B3 mean?

The SE-B3 is a BITZER compressor protection device for 110-240 V supplies that monitors motor winding, discharge-gas and oil temperature. When the preset temperature is exceeded the device locks out immediately and stops the compressor. It also provides broken-sensor-lead monitoring and replaces the SE-B1 and SE-B2 at 110-240 V with identical function and terminal layout.

Symptoms

• Compressor tripped and held off by the safety chain
• Protection relay open after a high-temperature event
• Device remains locked after the fault clears
• No restart until the supply is briefly cut

Common causes

• Winding, discharge-gas or oil temperature over the preset threshold
• Open circuit (broken lead) in the temperature-sensor wiring
• Compressor overheating from overload or poor cooling
• Defective PTC temperature sensor

Diagnostic steps

1. 01

   Determine the trip cause

   Establish why temperature rose before resetting; the device stays locked until the fault is found and corrected.

2. 02

   Allow cooldown

   Let the compressor and oil cool so the temperature sensors return to their normal range.

3. 03

   Inspect sensor leads

   Check the winding-temperature sensor circuit for breaks, since the SE-B3 also locks out on a broken lead.

4. 04

   Unlock the device

   Interrupt the protection-device supply voltage for at least five seconds, then re-energize to clear the lockout.

5. 05

   Verify supply variant

   Confirm the 110-240 V supply variant is correct for the installation before restoring operation.

When to call a professional

Only trained, authorized specialists may work on the compressor and its system. Repeated lockouts after cooling indicate a real over-temperature or motor fault that needs professional diagnosis. Wiring of the protection device, the safety chain and any internal compressor problem should be referred to a qualified refrigeration technician familiar with EN/UL 60730 devices.