ZHB Series Start-up and Overload Protection Relays (ZHB35-120P15 / ZHB62-140P15) for Refrigerator Compressors
Combined ZHB series start-up and protection units integrate a PTC starter element and a bimetallic thermal overload relay (klixon) in a single housing. They are designed for the safe starting and continuous protection of compressor windings against overload and overheating.
1. Main Technical Specifications
- Operating Voltage: 220–240 V / 50 Hz.
- PTC Resistance: 15 Ohm (P15 index).
- Design: Monoblock (start + thermal relay) with 3 contacts/sockets for compressor pins.
2. Model Comparison and Compressor Selection
Models differ by compressor power and thermal protection trip thresholds. Use the table below for correct selection:
| Characteristic | ZHB35-120P15 | ZHB62-140P15 |
|---|---|---|
| Compressor Power | Low / Medium (110–140 W) | High (180–240 W and above) |
| Current Protection Threshold | ~3.5 A (for low-power motors) | ~6.2 A (for high-power motors) |
| Cut-off Temperature | 120 °C | 140 °C |
| PTC Resistance | 15 Ohm | 15 Ohm |
| Compatibility | Domestic single-door and small double-door refrigerators | Large double-door refrigerators, chest freezers, commercial equipment |
3. Why Correct Model Selection is Important
- If ZHB35 is installed instead of ZHB62: The relay will trip falsely ("click") and shut down a working compressor due to exceeding the starting current threshold.
- If ZHB62 is installed instead of ZHB35: The protection will not cut off power in time if the motor stalls, which will lead to the compressor windings burning out.
4. Installation Recommendations
- De-energize the equipment: Completely disconnect the refrigerator from the power supply before installation.
- Check the contacts: Ensure the compressor pins are clean and free of oxidation or carbon deposits.
- Installation: Firmly press the ZHB unit onto the compressor pins until it is fully seated.
- Connection: Connect the power wires strictly according to your refrigerator's wiring diagram.
