Samsung AM072BXV Series Service Manual page 249

Piping Diagram
7-3 Functions (cont.)
7-3-2 Control (cont.)
7-3-2-4 Special operation modes
Defrost operation
▪ Purpose
Optimize the heating performance by removing frost from the outdoor heat exchangers in heating mode.
▪ Concept
- Heat exchangers are checked for frost formation based on the heat exchanger temperature (Cond out, Suction) and
the heating duration.
- Cooling mode is on until the heat exchanger temperature (Cond out, Suction) reaches a specific level.
- If the heating duration indicates that defrost mode should start, the heat exchangers are checked for frost formation based on the
electric current rise of the outdoor fans and then heating mode is on for a maximum of 18 hours (learning-based defrost)
▪ Control specifications in detail
- Criteria used to decide whether to use defrost mode include the heat exchanger temperature (Cond out, Suction) and the heating
duration.
- Checking the heat exchanger temperature starts 30 minutes after Safety Start mode turns off. Defrost mode starts if the Cond out or
Suction temperature of each outdoor unit is -5℃ or lower and there is a sufficient degree of difference between the outdoor tempera-
ture and the Cond out or Suction temperature.
- Checking the duration starts after Safety Start mode turns off. Defrost mode starts if the outdoor temperature is 0℃ or higher and
heating mode has been on for 2 hours under the following condition: the Cond out temperature is lower than 2℃ and the low pres-
sure is 6.2kgf/cm2,g or lower. Defrost mode can also start if the outdoor temperature is below 0℃ and heating mode has been on
for 2 hours under the following condition: the low pressure is 6.2kgf/cm2,g or lower and there is a sufficient difference between the
outdoor temperature and heat exchanger temperature.
- The learning-based defrost feature learns the electric current in the fan when there is no frost formation in 3-cycle heating mode. The
feature extends subsequent defrost mode, started based on the heating duration, up to 18 hours if the electric current in the fan does
not rise by 8% or more compared to the frost-free state .
- Condition(s) required to turn off defrost mode: Cond out temp ≥ 12℃ OR 15 min after defrost mode has started.
Actuator
Compressor
Outdoor EEV
Outdoor Fan
Indoor EEV
Indoor Fan
Time
Samsung Electronics
Active unit
Inactive unit
Active unit
Inactive unit
OFF (if using the HR device, model-based control is performed on cooling indoor
Behavior during defrost mode
Depends on the outdoor unit capacity (86-110Hz)
Depends on the outdoor unit capacity (50-60Hz)
Full open
Starts with 0 step and controls cooling fans
800 step
400 step
units while in main heating mode)
Maximum of 15 min
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