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8.0 SYSTEM OPERATION
1. Control logic description
This frequency conversion system adopts the exactly same control logic as that of
common fixed frequency unit. Start-up demand signal is sent by wired controller or
indoor unit and when outdoor unit receives the signal, it will start required mode accord-
ing to demand. Start-up demand signal is the common 24V control signal.
Compressor operating frequency is controlled by outdoor unit completely.
To ensure stable and adequate power output, target control low pressure evaporating
temperature Te when cooling and target control high pressure condensing temperature
Tc when heating, control and adjust compressor PI according to control target demand.
Meanwhile, Te and Tc target demand has the function of self-study according to com-
pressor operating frequency, start/stop times so that to adjust power output autono-
mously ensure to well satisfy power demand load.
It can choose the initial settings of Te and Tc according to dehumidification and high
capacity demands by manually adjusting the dial code as well so that to satisfy relative
demands.
2.Sensor description
A working T3 Sensor is required for:
● Operating protection (high temp./low temp.)
● Outdoor fan control(cooling)
● (Heat pump only）Defrost （Heat pump only）
● Ambient temp forecast （Cooling only）
A working T4 Sensor is required for（Heat pump only）:
● Operating condition permission
● Defrosting condition determination
● Outdoor fan control(heating mode, Heat pump only)
A working T5 Sensor is required for:
● Protection(high temp./low temp.)
● Outside EEV control valve （Heat pump only）
A working Tf Sensor is required for:
● Module temp. protection(high temp.)
A working Pressure Transducer Sensor is required for:
● Operating frequency control
● Outside EEV control valve （Heat pump only）
● High pressure protection(heating mode, Heat pump only)
● Low pressure protection(cooling mode)
2、Defrost description
● Outdoor defrost control needs to measure T4 ambient temp. sensor and T3 coil temp.
sensor. When difference value between the two sensors has satisfied some condition,
defrosting will begin. Meanwhile, Meanwhile， when operating in the condition of a low
ambient temp.for a certain period or system high pressure side pressure is lower than a
certain value, the system will enter defrosting mode.
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