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5.4.5 Four-Way Valve Control 
In heating mode, a four-way valve is opened.  
In defrosting, a four-way valve operates 
according to the current defrosting action.  
In other modes, a four-way valve is closed.  
When the unit is switched from heating to other 
modes, the four-way valve turns off after the 
compressor has been off for 2 consecutive 
minutes.  
Failure or protection (excluding discharge 
temperature protection and high/low pressure 
protection) causes the four-way valve to 
immediately shut down.