Outdoor Unit Control Mode - Friedrich FPHMR18A3A Service Manual

Outdoor unit Control Mode

1. Cooling Anti-freeze Protection
To prevent freezing caused by too low temperature of indoor evaporator, the air conditioner will implement real-time
detection over the indoor coil temperature. If the indoor coil temperature is too low, the compressor will be prohibited from
increasing or decreasing the frequency or shutting down automatically.
2. Heating Overload Protection
To prevent system overload caused by excessive pressure in heating operation, the unit will implement real-time detection
over the indoor fan-coil temperature: If the indoor coil temperature rises, the compressor will be prohibited from increasing
the frequency; If the temperature continues to rise, the compressor will decrease the frequency; If the indoor coil
temperature is too high, the compressor will stop working immediately. The compressor then will reboot after the indoor coil
temperature reduces.
3. Cooling Overload Protection
To prevent system overload due to excessive pressure during cooling operation, the unit will implement real-time detection
over the outdoor condenser coil temperature: If the outdoor coil temperature rise, the compressor will be prohibited from
increasing the frequency; If the temperature continues to rise, the compressor will decrease the frequency; If the outdoor
fan-coil temperature is too high, then the compressor will stop working immediately. The compressor will reboot after the
outdoor coil temperature reduces.
4. Discharge Temperature Protection
To prevent working conditions of compressor from deteriorating due to high discharge temperature, the unit will
implement real-time detection over the discharge temperature. If the discharge temperature rises, the compressor will be
prohibited from increasing the frequency; if the temperature continues to rise, the compressor will decrease the frequency
automatically; if the discharge temperature is too high, the compressor will stop working immediately. The compressor will
then reboot when the discharge temperature returns to the normal condition.
5. Oil Return Control
When the compressor continues to operate at low frequency, there will be an oil return. The
compressor increases the frequency, and thus returns the oil in refrigerant system to the compressor.
6. Operation Mode
Mode Category b. Mode conflict
Air conditioning mode is the operation mode set by users through the remote controller. Four modes are available: cooling, The operating mode of outdoor unit is decided by the operating mode of the indoor unit firstly
heating, dehumidification, and fan mode.
booted. Indoor unit subsequently booted will firstly determine whether it's own mode is conflict
Mode conflict
with the outdoor mode. If so, the indoor unit will automatically shut down after three beeps; If
The operating mode of outdoor unit is decided by the operating mode of the indoor unit that is booted first. Indoor units
there is no conflict, the indoor unit will boot normally. The relationship of mode conflict is as
subsequently booted will determine whether it's own mode is conflict with the outdoor mode. If so, the indoor unit will
follows:
automatically shut down after three beeps; If there is no conflict, the indoor unit will boot normally. The relationship of mode
conflict is as follows:
Driven choice
Active mode
Cooling
Dehumidification
Heating
Fan
√ Mode conflict will not happen
× Mode
√ Mode conflict will not happen
7) Outdoor four-way Valve Control
× Mode conflict will happen
Four-way valve of the outdoor machine shuts down when cooling but starts when heating.
The operation of heating defrosting refers to defrosting operation and, when the heating remote
46
shutdown, the four-way valve disconnects in 50s when the compressor stops working.
8) Start-up Protection
To prevent compressor from restart frequently in the condition that system pressure has not been
completely balanced, it can't be restarted within 3 minutes.
OPERATION
Cooling
√
√
×
√
conflict will happen
Dehumidification
√
√
×
√
Heating fan
√
×
√
×
√ ×
√
×