GREE H5 Error Code IPM Protection Instruction Manual

What the H5 Error Code Means

H5 is displayed on the indoor unit and indicates IPM (Intelligent Power Module) protection. The system has detected either an IPM synchronization issue or an overcurrent condition. If the IPM does not provide adequate power to the Drive Chip, the system shuts down to protect itself.

Power Conversion Path

Power flows from the incoming 230 V AC through the bridge rectifier into the Power Factor Correction (PFC) module, which outputs a DC bus typically in the 290–340 V DC range. That DC bus feeds the Intelligent Power Module (IPM), which converts the DC voltage into three separate pulses, one per compressor phase, to drive the compressor

How the System Detects H5
The outdoor main control board monitors three indicators on the PFC module:

Output Voltage
Monitored on the PFC module output.

Output Current
If PFC output current is too high, the system reports H5 as an overcurrent error.

PFC Module Temperature
A failure in any monitored indicator tells the system the PFC module is faulty.

H5 Root Causes

The H5 error has multiple possible causes that range from installation and refrigerant issues to drive board electrical faults to a failed compressor. Work the basics first, most H5 calls do not require a board or compressor replacement once airflow, refrigerant charge, and wiring are verified.

Installation & Airflow

• Inadequate airflow at indoor or outdoor coil
• Service valves not fully open or system not properly evacuated
• Crossed piping between zones (multi-zone systems)
• Restriction or kinked refrigerant line

Refrigerant

• Non-condensibles in the refrigerant system (standing pressure does not match outdoor temperature on the PT chart)
• System overcharge or undercharge

Electrical & Mechanical

• Compressor wiring loss of phase or phase reversal
• Current to the compressor too high (overcurrent)
• Drive board IPM module 15 V power supply below 13.5 V
• Drive board six-line PWM signal or corresponding element faulty
• Drive board compressor current sampling element, or the Drive Chip current sampling AD terminal, faulty
• Faulty thermistors – See the thermistor ohm chart here
• Heat-sink paste or board screws not properly seated
• Compressor itself: open winding, shorted to ground, or seized

Step-by-Step Troubleshooting: Steps 1–3

Start with airflow and installation, then refrigerant pressures, then wiring. The same order applies whether the unit was just installed or has been running for years.

Verify Airflow and Installation

• Confirm indoor filters, coils, and blower wheels are clean
• Confirm the outdoor coil is clear with proper clearance around the unit
• Verify all service valves are open and the system has been properly evacuated

Check Refrigerant Pressure Against the PT Chart
Compare standing pressure to outdoor temperature using the PT (pressure-temperature) chart for the system’s refrigerant. If pressures do not match what the chart predicts for the ambient, the system may have noncondensibles, which can directly cause an H5 error. Recover, evacuate, and recharge if noncondensibles are confirmed.

Inspect Wiring and the Main Board

Inspect the wiring against the unit’s diagram and check the main board for visible damage. All screws on the board must be installed and tightened so heat transfers correctly through the thermal paste to the heat sink. Missing this step is a common reason a newly-replaced board fails on the first run. All board screws must be installed and tightened. Missing or loose screws prevent heat transfer through the thermal paste and can cause a newly-replaced board to fail on the first run.

Troubleshooting Step 4: Test the Compressor Windings

Power off the system and unplug the leads at the compressor. Set the meter to ohms.

Phase-to-Phase Test
Test the windings phase-to-phase between U-V, U-W, and V-W.

• FLEXX R32 compressors: 0.3 to 2 ohms
• Other R32 mini-split compressors: 3 to 4 ohms
• Readings should be roughly equal or within .01 ohms across all 3 pairs.

If you’re uncertain which range applies to the model in front of you, call GREE technical service at 888-850- 7928 before condemning the compressor.

Winding-to-Ground Test
Test each winding to ground.

• Resistance to ground should be infinite (open line)
• A measurable ohms reading to ground indicates the compressor is grounded
• A mega-ohm reading to ground does NOT indicate a grounded compressor

Troubleshooting Steps 5–6: Amperage & Continued Trips

Step 5: Restart and Check Compressor Amperage. Restore power and restart the system. If the compressor does not start, check amperage on all three legs. Timing matters when reading amps: the condenser fan runs for about 30 seconds before the system tries to start the compressor, and the start attempt only lasts a few seconds before the unit drops out. You are only looking for some kind of amp draw on that leg, which can be anywhere from roughly 0.3 or higher. After the unit drops out, wait for the condenser fan to cycle back on before testing the next wire, and repeat for each leg.

Amps present on all legs but compressor will not start: compressor is likely seized
No amps on one or more legs: the main board has failed

Step 6: Compressor Runs but Still Trips H5
If the compressor runs but the system trips H5 once it ramps up, the cause is most likely one of:

• System overcharge
• Refrigerant restriction
• Kinked refrigerant line
• Inadequate airflow
• Crossed piping (multi-zone systems)
• Faulty thermistor

Verify each before assuming a drive-section electrical fault.

Drive Section Board Tests

Drive-section testing on the main board has four parts. All four tests together confirm the bridge rectifier, PFC module, and IPM are good. Use the board diagrams in the unit’s service manual to locate test points.

K-Ohms Resistance Test (Power Off)
Set the meter to K-ohms. Measure resistance between PU, P-V, P-W, N-U, N-V, and N-W. All six readings should be above 10 K-ohms with no large differences between them.

Diode Test (Power Off)
Set meter to diode test mode. Place the black lead on P, red lead on each of U, V, and W in turn. Place the red lead on N, black lead on each of U, V, and W in turn. All six readings should be between 0.3 V and 0.7 V.

Powered DC Voltage Test (P to N)
Restore power. Set meter to DC volts. Test discharge points P (positive) and N (negative) on the board. Voltage should be between 290 and 340 volts DC.

Powered AC Voltage Test (L to N)
Set meter to AC volts. Test L (live) and N (neutral) terminals on the PCB. Expected: 187 to 253 V AC for a 230 V unit; 103 to 126 V AC for a 115 V unit. Wiring note: In the U.S., L1 = 115 V and N = L2 (the other side of 230 V). Outside the U.S., 230 V is sent straight to L1. If any reading is out of range, that section of the board is the fault and the board needs to be replaced.

Quick Reference: Healthy H5 Test Values Use this table to verify readings at each test point.