GREE                                                                        GMV5E DC INVERTER VRF UNITS SERVICE MANUAL 
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3 Key Parts Maintenance 
3.1 Cautions on Controller AP1 Replacement 
3.1.1 Cautions on ODU AP1 Replacement 
3.1.1.1 Distinguishing Master Module from Slave Module 
Before replacing ODU AP1, determine the module is a master ODU or a slave ODU. They can be 
distinguished based on: 
① “Master module DIP state (SA8_MASTER-S)”
 
Every cooling system has only one master module (set in power-off state). When a DIP is “ON”, the 
corresponding  position  is  “0”;  when  the  DIP  is  “OFF”,  the  corresponding  position  is  “1”.  If 
SA8_MASTER-S is set to “00”, it indicates a master module; if it is set to “10”, it indicates a slave module 
(as shown in the figure below). 
 
 
② AP1 LED 
When a master module is powered on, LED1 is displayed as “01”. For a slave module, LED1 is 
displayed as “02”, “03” or “04” (as shown in the figure below).   
 
3.1.1.2 Cautions on Replacement of Master ODU AP1 
Before replacing master module AP1, make the following preparations: 
① Master module DIP setting 
Set the new AP1 identical to the faulty AP1. Note that settings must be performed when the master 
ODU is powered off and they will take effect after the ODU is powered on. Settings that are performed in 
power-on state are invalid.