Outdoor Unit Control Mode - Friedrich FPHFR9A3A Service & Parts Manual

OPERATION

Outdoor Unit Control Mode

Control function
Cooling Anti-Freeze Protection
The indoor coil sensor functions as real time temperature detector of evaporator. It prevents the indoor unit evaporator temperature
becoming too low. If the indoor coil temperature is too low, the compressor will automatically start protection mode.
Overload Protection
To prevent system overload caused by excessive pressure, the machine will implement real‑time detection when outdoor coil
temperature is too high during cooling mode or indoor coil temperature is too high during heating mode.
Exhaust temperature protection
To prevent deterioration due to high exhaust temperature of compressor, the machine will realize the real‑time detection of the
exhaust gas temperature. If the temperature is too high, the compressor provides automatic protection.
Oil-return Control
When the compressor runs at low frequencies for a long time, the control system will start the oil‑return mechanism. The oil in the
system returns to the compressor.
Operation Mode
Air conditioning mode is the operation mode set by users through remote controller, four modes are available: cooling, heating,
dehumidification, and fan mode.
Four-way Valve Control
Four‑way valve of the outdoor unit shuts down when cooling and defrosting but starts when heating. During the heating process, the
four‑way valve stops working for a period of time after compressor is disconnected.
Start-up Protection
To prevent compressor from restarting frequently when the system pressure has not been completely balanced, it cannot be
restarted within 3 minutes.
Pressure Protection
When the pressure increases to a preset value, the pressure switch will automatically protect the unit. The compressor will stop and
report the fault code protection.
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