Trane TVR Pro CO Series Service Manual page 77

2.12 H2, H3: Slave units decreased/increased
Digital display output
Description
 H2 indicates that the number of slave units detected by master unit has decreased.
 H3 indicates that the number of slave units detected by master unit has increased.
 All units stop running.
 Error code is only displayed on the master unit.
Trigger / recover condition
 Trigger condition: Number of slave units detected by master unit has decreased or increased.
 Recover condition: Number of slave units detected by master unit goes back to normal.
 Reset method: Resume automatically.
Possible causes
 Some outdoor units are powered off.
 Power supply abnormal.
 Incorrect outdoor unit address setting.
 Communication wires between outdoor units not connected properly.
 Loosened wiring within electric control box.
 Damaged main PCB or electric control box communication terminals block.
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