General Assist Technical Reference
J Series Protective Function List
Compressor, pressure, temperature and inverter protection controls
Technical reference for J Series protective functions, detection conditions and resulting control actions.
The J Series continuously monitors refrigerant temperatures, heat exchanger temperatures, system pressure, current and inverter conditions. When a protection threshold is reached, the system may reduce compressor speed, operate a solenoid valve or stop the compressor to protect the equipment.
Service note: A protective function operating does not by itself identify the underlying fault. Confirm the relevant sensor, pressure switch, refrigerant circuit, electrical condition and associated service data before replacing components.
1. Temperature protection overview
| Protection | Primary detection | Control response |
|---|---|---|
| Discharge temperature | Discharge temp thermistor | Progressive compressor speed reduction, SV2 operation, or compressor stop depending on protection level. |
| Cooling overload | Heat exchanger mid thermistor | Compressor speed reduction or SV1 operation. |
| Heating overload | Heat exchanger mid thermistor (indoor unit), maximum value | Compressor speed reduction or SV1 operation. |
2. Pressure protection overview
| Protection | Detect part | Result |
|---|---|---|
| High pressure protection | Pressure switch 1 | Compressor stops. High pressure error is generated after repeated operation as listed below. |
| Low pressure protection 1 / 2 | Pressure switch 2 | Compressor stops. Error criteria vary according to the protection stage and timing condition. |
3. Electrical and inverter protection overview
- Active filter detected protection: Stops the compressor when an open condition is detected in the active filter element.
- Active filter over voltage protection: Stops the compressor when excessive voltage is detected.
- Current release protection: Reduces compressor speed by 1 Hz every 2 seconds until the current returns to the release value.
- IPM over current: Stops the compressor when the detected current reaches the specified range.
4. Protective function list
| No. | Protective Function | Detect Parts | Condition of Protection Detective | Function |
|---|---|---|---|---|
| 1 | Discharge temp protection 1 | Discharge temp thermistor | Start: 108°C more. Release: 100°C less (120sec) | Compressor speed is decreased by 10Hz/120 sec until it becomes lower than 108°C. |
| 2 | Discharge temp protection 2 | Discharge temp thermistor | Start: 103°C more. Release: 88°C less (120sec) | SV2 is opened. |
| 3 | Discharge temp protection 3 | Discharge temp thermistor | Start: 118°C more. Release: 93°C less (10min) | Compressor stops. Discharge temperature error by 3 times within 40 min. |
| 4 | Cooling overload protection 1 | Heat exchanger mid thermistor | Start: 59°C more. Release: 52°C less (120sec) | Compressor speed is decreased by 10Hz/120 sec until it becomes lower than 59°C. |
| 5 | Cooling overload protection 2 | Heat exchanger mid thermistor | Start: 61°C more. Release: 52°C less (120sec) | SV1 is opened. |
| 6 | Heating overload protection 1 | Heat exchanger mid thermistor (Indoor unit) Maximum value | Start: 56°C more. Release: 47°C less (120sec) | Compressor speed is decreased by 10Hz/120 sec until it becomes lower than 47°C. |
| 7 | Heating overload protection 2 | Heat exchanger mid thermistor (Indoor unit) Maximum value | Start: 57°C more. Release: 47°C less (120sec) | SV1 is opened. |
| 8 | High pressure protection | Pressure switch 1 | Start: Pressure SW OFF [609psi (4.2MPa) more] Release: Pressure SW ON [464psi (3.2MPa)] | Compressor stops. High pressure error by 2 times within 20 min. |
| 9 | Low pressure protection 1 | Pressure switch 2 | Start: Pressure SW OFF 10 minutes. 20 min after compressor started up Release: Pressure SW ON 3 minutes comp stop | Compressor stops. Low pressure error by 2 times within 40 min. |
| 10 | Low pressure protection 2 | Pressure switch 2 | Start: Pressure SW OFF A compressor starts for the first time and it is less than 1 minute. Release: Pressure SW ON 3 minutes comp stop | Compressor stops. Low pressure error by 5 times within 30 min. |
| 11 | Active filter detected protection | Element in active filter | Start: Detected open Release: Release open detection | Compressor stops. |
| 12 | Active filter over voltage protection | Element in active filter | Start: Detected excessive voltage Release: Release excessive voltage detection | Compressor stops. |
| 13 | Current release protection | Detect circuit in PCB | Start: Setting current limit value ※1 Release: Setting current limit value-1A | Compressor speed is decreased by 1Hz / 2 sec until it becomes to the release current value. |
| 14 | IPM over current | Element in IPM | Start: Detected current 61.4∼83.8A Release: Release by compressor stop | Compressor stops. Abnormal stop by detecting 5 times within 40 sec after start-up. |
※1: Depends on DIP-SW setting.
5. Practical diagnostic use
- Identify which protective function is active or which error history is being recorded.
- Use the Detect Parts column to identify the sensor, switch, PCB circuit or IPM element involved in the protection logic.
- Compare the actual operating condition with the listed start and release thresholds.
- Where the function reduces compressor speed or opens SV1/SV2, confirm whether the system recovers before the higher-level protection is reached.
- Where repeated compressor stops generate an error, check the repetition count and time window shown in the table.
Technical information reproduced from the supplied J Series protective function reference. Always confirm model-specific service documentation before applying values to a unit in the field.