Our new Deye 15 kW hybrid went bang the first time we switched on the PV strings and showed F21, F47 and later F55. Installation fault or inverter fault, and what should we check?

Plain explanation

The manual says F21 is 'BUS over current', F47 is 'AC over frequency' and F55 is 'DC busbar voltage is too high'. Its checks are: PV input voltage within the allowed range (max PV input 800 V, MPPT range 160 to 650 V for this model), battery voltage and current settings, battery polarity ('Reverse polarity connection on battery will damage the inverter'), and firm, correct AC cables. Its standard advice for F21 is to restart 2 to 3 times. After a bang or a burning smell, though, our advice is: do NOT restart. Switch off the DC isolator and the battery breaker, disconnect AC, and get it inspected. In the Reddit case the owner reported that Deye inspected the unit, found an internal defect, replaced the power/driver board, updated the firmware and found no wrong settings. Then the CTs were set up again and the system now runs normally.

Steps from the source

1. Switch off: DC isolator, battery breaker, AC breaker; do not power-cycle after a bang
2. Measure each string's Voc with a meter and compare it to the 800 V maximum (with cold-weather margin)
3. Check battery polarity and cable lugs; check AC wiring and torque
4. Photograph the fault log (F21/F47/F55 with timestamps) and send it with serial number to the installer and Deye
5. After repair, re-commission step by step and re-set the CTs

"Reverse polarity connection on battery will damage the inverter."

Word for word from the source.

Source

Where installers ask this

• Update zu Deye SG05 15 kW / Knall bei erster Betriebnahme / Fehler F21 und F47 (r/DeutschePhotovoltaik)
• reddit.com/r/DeutschePhotovoltaik/comments/1vvm4fx/
• https://akkudoktor.net/t/deye-sg05-15-kw-knall-bei-einschalten-des-dc-schalters-fehler-f21-und-f47/41024
• https://dy-support.org/community/technische-fragen/deye-sg05-15-kw-pv-string-knallt-bei-erster-inbetriebnahme-fehler-f21-und-f47/

General guidance based on the manufacturer's manual or the named source. Always follow the current manual for your exact model and your national code. DC and AC electrical work is for qualified installers only. Not affiliated with or endorsed by any brand named; trademarks belong to their owners.