A: Troubleshooting steps:
1. This alarm occurs when the actual supply‑return air temperature difference of the unit is less than the "supply‑return air temperature difference threshold".

2. At this point, check the actual difference between the supply air temperature and the return air temperature. If the difference is indeed below the threshold, it is a normal alarm. You can check the supply and return water temperatures, then adjust the threshold to clear the alarm.

3. If, after inspection, the supply‑return air temperature difference is confirmed to be greater than the alarm threshold, you need to provide the alarm history and software version number, and contact the manufacturer for further handling.