Daikin FTXN25L - Defrost Cycle; Indoor Coil Freeze Prevention

Algorithm & Control
26
2.16.4 PI Control
P control:∆Tofeachindooriscalculatedateverysamplingtimeof20sandcompressorrotationisadjusted
according to the difference from the previously calculated rotation.
I control:iftheoperatingfrequencyisnotchangedmorethanacertainxedtime:
• IfΣ∆Tissmall:lowerfrequency.
• IfΣ∆Tislarge:increasefrequency.
2.16.5 Limit Rotation
Determine from
• Upper limit rotation
A minimum value was determined among the upper limits rotation, i.e. protection controls.
• Lower limit rotation
A maximum value was determined among the lower limits rotation, i.e. protection controls.
Generally, compressor rotation is controlled within 5 zones: stop, drop, keep, up and reset subjected to a
particular operating temperature/current/pressure.
Zone Control
Stop
Compressor is stopped when a certain limit reaches the stop zone for abnormality
correction.
Drop Frequency will be dropped with a timer setting.
Keep Frequency is maintained at lower/upper limit.
Up Frequency will be increased with a timer setting.
Reset Frequency lower/upper limit is canceled and returned to command rotation.
2.17 Defrost Cycle
During defrost All models
Compressor ON
4-way valve OFF
EXV in operation room Fixed opening
Outdoor fan OFF
Indoor fan OFF
Condition for entering defrost
• Compressorminimumruntime–6minutesOR
• Compressoraccumulatedruntimeof45minutesifOutdoorcoil<3°C.
Condition for terminating defrost
• Outdoorcoil>12°Cor
• Total defrost timer of 650 seconds.
2.18 Indoor Coil Freeze Prevention
Only available in cooling mode.
Whentheindoorcoiltemperature<2°C,thecompressorstartstodropthefrequency.
This protection will cut in when:
• Indoorcoiltemperature<0°Cformorethan180s.Compressorwillstop,outdoorfanstopafter30sand
indoor fan can only run at lowest fan speed.
The unit can only be restarted after 3 minutes.
Whentheindoorcoiltemperature>13°C,thecompressorfrequencywillberesetbasedontheoutdoor
ambient, room and set temperature.