HVACopediaKinghome · Heat pump
H4 Overload protection (high condensing pressure)
What the control is telling you
Condensing pressure exceeded its protection value on Ultranixx units.
Applies to: Kinghome Ultranixx Eco KD24UHO to KD60UHO outdoor units with KD..UHI air handlers; Kinghome Ultranixx cold-climate KU36UHO and KU60UHO outdoor units with KU..UH2I and KD..UHI air handlers
Likely causes
- Blocked outdoor or indoor coil
- Ambient above operating range
- Overcharge
Test and repair steps
- Clean the coils.
- Check ambient limits.
- Release a proper amount of refrigerant if overcharged.
- Replace the drive board then compressor if the code persists.
Models that show this code
18 models in Kinghome Ultranixx Eco, Kinghome Ultranixx
Other codes on the same units
- F3 Outdoor ambient temperature sensor fault
- F4 Sensor fault (outdoor condenser or discharge)
- F6 Frequency limit for overload / ODU tube sensor fault
- H3 Compressor overload protection
- H5 IPM module protection
- H6 Fan motor feedback fault (indoor or outdoor)
- H7 Compressor out-of-step
- P0 Compressor minimum-frequency test / driver reset
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Source: Kinghome Ultranixx Eco KD24-60UHO service manual, sec. 3.3-3.4; Kinghome Ultranixx cold-climate KU36/60UHO service manual GC202306, sec. 3.3-3.4. Summarized in our own words; check the original manual for your model.
Homeowner looking at this code? See what it means for you and when to call a technician.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.