Fault codes covered
39-15, 39-55
A code 39-15 is declared when VFD commanded speed is above 200rpm and actual speed is reduced to less than 80rpm as reported via VFD for 10 seconds consecutively after starting. The fault triggers compressor and fan shutdown, then VFD reset. If demand is still present the system will attempt to restart normally and run. An intermittent open connection on fan FG wire or a failing fan motor may create these faults.
Source: ACHPVSR454-02SM troubleshooting pages.