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SS-SVM001A-EM
16. Control logic description
16.1 An illustration to outdoor unit signal
16.2 Cooling Mode
(1) Communication between indoor and outdoor units:
The communication between the outdoor unit, thermostat and the indoor unit is achieved
through 24V alternating current, as shown in figure below.
The thermostat controls the signal output of Y, if Y-C is high level, the outdoor unit starts
in cooling mode.
W-SI signal is send when outdoor unit runs with low-frequency mode.
(1) Start conditions:
When high level compressor signal is received from the thermostat, that is Y-C is high level.
(2) Stopping operating:
① Stopping conditions:
When low level compressor signal is received from the thermostat, that is Y-C is low level.
② Actions:
The compressor keeps operating with its current frequency, and detects its system pressure
at the same time.
(a) If the pressure changes more than 0.04MPa【e2】in 10 seconds, the compressor stops
operating.
(b) If the pressure changes less than 0.04MPa【e2】in 10 seconds, the compressor keeps
operating and the target pressure is set to increase by 0.2MPa【e2】based on the current
system pressure. The motor and electronic expansion valve are controlled as usual, the
protection function and oil-return control are valid.
③ Stopping conditions:
When the compressor signal received from the thermostat is high level, that is Y-C is high
level, the unit restores the normal target pressure to operate or when the compressor has
operated for 30min【e2】with the increased target pressure, it is taken as it has stopped
operating.
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