Fault Handling Document for E20 IPM Abnormal Protection of  Heat Pump

1. Fault Overview

E20 is the fault code for IPM (Intelligent Power Module) abnormal protection. As the core component of the heat pump compressor drive system, the IPM is responsible for converting direct current into controllable three-phase alternating current to drive the compressor. According to the document, E20 includes multiple sub-fault types, as detailed below:

2. Causes of Faults

1. IPM Module Internal Failures

• Module overcurrent: Sudden overload of compressor (such as liquid compression), reversed wiring of compressor U/V/W leading to reverse rotation, increased load caused by compressor oil shortage/liquid compression-induced cylinder wear, mismatch between program and compressor leading to abnormal drive current.
• Module over-temperature: Low speed or stop of IPM module cooling fan, excessive dust accumulation on heat sink leading to poor heat dissipation, sudden rise of ambient temperature exceeding the heat dissipation capacity of the module, aging of internal power components leading to increased heat generation efficiency.
• Module hardware damage: Breakdown of internal power components due to long-term high-load operation, damage to module circuit caused by voltage impact.

2. Power Supply System Failures

• AC side abnormalities: Overvoltage/undervoltage of input power supply, phase loss of input power supply, sudden AC input overcurrent (such as insufficient frequency reduction when load increases suddenly).
• DC side abnormalities: DC bus voltage exceeding the protection threshold (overvoltage or undervoltage), PFC circuit failure leading to ineffective power factor correction and bus voltage fluctuation.

3. Communication and Control Failures

• Communication abnormality between main control board and drive board: Loose or damaged communication cables between main control board and drive board, failure of communication interface circuit, abnormal main control board program leading to interruption of communication data.
• Current detection failure: Damage of inverter current transformer during transportation, reversed installation direction of transformer during production, misjudgment caused by excessively small current when idle compressor runs at high frequency without load.

4. Associated Component Failures

• Compressor failures: Compressor cylinder sticking, shaft seizure, winding short circuit, etc., leading to abnormal load; compressor phase loss and out-of-step causing drive system failures.
• Cooling system failures: Cooling fan motor failure, abnormal fan control circuit, blocked cooling air duct leading to insufficient heat dissipation of IPM module.

3. Fault Troubleshooting Steps

Step 1: Confirm Sub-fault Code

1. Enter the unit debugging mode or use special monitoring software to read the sub-fault code of E20, clarify the specific fault type, and carry out targeted troubleshooting.
2. If the sub-fault code cannot be read, first record the unit operating status (such as operating mode, ambient temperature, operating duration when the fault occurs), then troubleshoot according to the general process.

Step 2: Visual Inspection After Power Off

1. Visual inspection of IPM module: Turn off the main power supply of the unit, open the drive board protective cover, and check whether the surface of the IPM module has bulging, ablation, or liquid leakage traces, and whether the heat sink has excessive dust accumulation.
2. Cable connection inspection:
   • Check whether the three-phase wiring of compressor U/V/W is loose or reversed, and whether the cables have damage or short circuit traces;
   • Check whether the communication cables between the main control board and the drive board are tightly plugged, and whether the cable outer sheath is damaged;
   • Check whether the wiring terminals of AC input power cables and DC bus cables are loose or discolored due to overheating.
3. Cooling system inspection: Manually rotate the IPM cooling fan to check whether the fan is stuck, and whether the air duct is blocked by dust or debris.

Step 3: Static Test After Power On

1. Power supply voltage test:
   • After power on (without starting the compressor), use a multimeter to measure the AC input voltage, and confirm that the voltage is within the range of ±10% of the rated value;
   • Measure the DC bus voltage. Under normal circumstances, it should be about 1.414 times the input AC voltage (e.g., 220V input corresponds to a bus voltage of about 310V). If the voltage is too high or too low, troubleshoot the PFC circuit or input power supply.
2. Communication test:
   • Use special monitoring software to connect to the main control board, check the communication status of the drive board. If communication interruption is displayed, replace the communication cable or troubleshoot the communication interface circuit;
   • Observe the communication indicator light of the drive board. If the indicator light does not flash or flashes abnormally, the communication failure is determined.
3. Current detection circuit test:
   • Measure the resistance value of the current transformer, and compare it with the resistance value of a normal transformer of the same model. If the deviation is too large, the transformer is determined to be damaged;
   • Check the installation direction of the transformer to confirm it is consistent with the marked direction.

Step 4: Dynamic Operation Test

1. Light-load trial operation: Set the unit to a low-load operation mode (e.g., reduce the target frequency to below 30Hz), start the compressor, and observe the unit operating status:
   • If E20 is reported immediately after startup, focus on troubleshooting compressor cylinder sticking, IPM module short circuit, and current detection failure;
   • If E20 is reported after a period of operation, focus on troubleshooting poor heat dissipation of IPM, compressor wear, and bus voltage fluctuation.
2. Parameter and program inspection:
   • Enter the parameter setting interface to confirm that the compressor matching parameters (such as rated current, overload protection threshold) are set correctly;
   • Check the program versions of the main control board and the drive board, confirm that the programs match the unit model, and upgrade the programs if the version is too low.

Step 5: Component Replacement Verification

1. If the IPM module is suspected to be faulty, replace it with an IPM module of the same model (pay attention to anti-static operation), and power on to test whether the fault is eliminated;
2. If communication failure is suspected, replace the main control board or drive board for cross-testing;
3. If compressor failure is suspected, disconnect the compressor wiring, connect an external dummy load with the same power for testing. If the drive system operates normally, the compressor is determined to be damaged.

4. Fault Handling Solutions

1. IPM Module Fault Handling

• Overcurrent/over-temperature failures:
  • If caused by excessive compressor load: Troubleshoot the causes of liquid compression (such as abnormal expansion valve opening, excessive refrigerant charge), adjust the expansion valve opening or release excess refrigerant; correct the compressor wiring sequence, and replace the worn compressor;
  • If caused by poor heat dissipation: Clean the dust on the IPM heat sink, replace the stuck or damaged cooling fan; improve the ventilation environment of the unit, and avoid operation in high-temperature environments;
• Module hardware damage: Directly replace the IPM module of the same model. Before replacement, confirm that there is no short circuit in the power supply system and load side to avoid damage to the new module again.

2. Power Supply System Fault Handling

• AC input abnormalities:
  • Overvoltage/undervoltage: Install a voltage regulator or contact the power supply department to adjust the power voltage;
  • Phase loss fault: Check the input power line, repair the loose or disconnected phase line;
  • Input overcurrent: Optimize the unit frequency reduction control program to ensure timely frequency reduction when the load increases suddenly, or replace the input fuse with a larger capacity;
• DC bus abnormalities:
  • Overvoltage/undervoltage: Troubleshoot the PFC circuit, replace the damaged PFC inductor, capacitor or switch tube; adjust the bus voltage protection threshold parameters;
  • PFC failure: Replace the PFC module or the PFC control chip on the drive board.

3. Communication and Control Fault Handling

• Communication abnormality between main control board and drive board: Re-plug the communication cable, replace the damaged communication cable; repair or replace the communication interface circuit of the main control board/drive board; upgrade the matching programs of the main control board and the drive board;
• Current detection failure: Replace the damaged current transformer, correct the installation direction of the transformer; repair or replace the sampling resistor, operational amplifier and other components of the current detection circuit.

4. Associated Component Fault Handling

• Compressor failures: Replace the compressor with cylinder sticking, shaft seizure or winding short circuit; replenish oil for the compressor with oil shortage;
• Cooling system failures: Replace the damaged cooling fan motor, clean the dust and debris in the air duct to ensure smooth heat dissipation.

5. Fault Recovery Verification

1. After fault handling is completed, power on and run the unit, check whether the E20 fault code is eliminated, and use the monitoring software to check whether the parameters such as current, temperature, and bus voltage of the IPM module are within the normal range;
2. Run the unit continuously for more than 4 hours, simulate different load conditions (such as full-load operation, start-stop test), and confirm that E20 fault is not reported again;
3. Check whether all functions of the unit (heating, cooling, DHW mode) are normal, and whether the compressor runs smoothly with no abnormal vibration.

5. Emergency Handling and Preventive Measures

Emergency Handling

When the unit reports E20 fault and shuts down, immediately turn off the main power supply to avoid fault expansion; if it is an IPM over-temperature fault, try to restart the unit after cooling for 30 minutes. If the fault is reported again, troubleshoot the cooling system.

Preventive Measures

1. Regular maintenance: Clean the dust on the IPM module heat sink and check the operation status of the cooling fan every 3 months; check the compressor wiring and communication cable connections every 6 months.
2. Parameter optimization: Reasonably set the IPM overcurrent and over-temperature protection thresholds according to the actual operating environment of the unit to avoid false protection or untimely protection.
3. Power supply guarantee: Install a UPS or voltage regulator in scenarios with unstable voltage to avoid voltage impact damage to the IPM module.
4. Program upgrade: Pay attention to the manufacturer's program updates regularly, and upgrade the programs of the main control board and the drive board in a timely manner to optimize the drive control logic.