Bitzer SE-B5

What does Bitzer SE-B5 mean?

The SE-B5 is a BITZER compressor protection device compliant with EN/UL 60730. It monitors motor winding, discharge-gas and oil temperature and locks out immediately when the preset temperature is exceeded. It also provides broken-lead and cable-short-circuit monitoring of the temperature sensor. When EN/UL 60730 compliance is required it replaces the SE-B1, SE-B2 and SE-B3.

Symptoms

• Compressor stopped after an over-temperature event
• Safety chain opened by the protection relay
• Device locked on a sensor short or broken lead
• Compressor stays off until manually unlocked

Common causes

• Winding, discharge-gas or oil temperature above the limit
• Short circuit in the temperature-sensor cable (too low resistance)
• Broken sensor lead (open circuit)
• Compressor overheating or sensor fault

Diagnostic steps

1. 01

   Identify the over-temperature or sensor fault

   The device locks until the cause is found and fixed; check whether a temperature limit was exceeded or a sensor cable shorted/broke.

2. 02

   Allow the compressor to cool

   Let temperatures fall back into range before testing a reset.

3. 03

   Test the sensor cable

   Check for a cable short (low resistance) or open circuit; per EN/UL 60730 a short in the temperature circuit is treated as a fault and locks the device immediately.

4. 04

   Unlock the device

   Interrupt the supply voltage to the protection device for at least five seconds, then restore power to clear the lockout.

5. 05

   Confirm compliance need

   Where EN/UL 60730 is required for compressor approval, ensure the SE-B5 (not an older SE-B device) is fitted.

When to call a professional

Work on the compressor and system is reserved for trained, authorized specialists. A sensor cable short or repeated thermal lockouts point to a wiring or motor fault that needs qualified attention. Because EN/UL 60730 compliance affects compressor approval, replacement, rewiring or diagnosis of this protection device should be done by a refrigeration professional.