The short answer
IEC 61215-2:2021 MQT 17 minimum is 25 mm ice balls (optionally larger). Sinovoltaics' reading of the standard table gives 23.0 m/s for 25 mm.
Plain explanation
IEC TS 63397:2022 restates that the hail test (MQT 17) of IEC 61215-2:2021 uses spherical ice balls of a minimum diameter of 25 mm, or optionally larger. Industry explainers of the same clause list 25 mm at 23.0 m/s as the baseline. That is a qualification minimum — hail-prone sites should specify a larger ice-ball size and a tougher sequence.
Steps from the source
- Treat 25 mm / MQT 17 as the certificate minimum, not a severe-hail proof
- For hail belts, specify a larger ice-ball diameter in the purchase spec
- Ask for the test report's actual diameter and velocity
"spherical ice balls of a minimum diameter of 25 mm, or optionally larger"
Word for word from the source.
Source
IEC TS 63397:2022 Photovoltaic (PV) modules – Qualifying guidelines for increased hail resistance (preview); Sinovoltaics explainer of IEC 61215-2:2021 MQT 17 hail test, IEC TS 63397 Introduction: MQT 17 minimum 25 mm; Sinovoltaics: 25 mm at 23.0 m/sassets.vde-verlag.de ↗
Where installers ask this
- Increase in hail size damaging solar panels? (r/solarenergy)
- reddit.com/r/solar/comments/136ofi3/hail_and_solar_panels/
- reddit.com/r/brisbane/comments/1p58y28/solar_panels_and_recent_hail/
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.