The short answer
The manual's check: PV string-to-PE resistance above 50 kΩ; also check PE. Rain-only faults may need a threshold reset.
Plain explanation
From the GoodWe manual for the ET / ET Plus+ / BT: Installer checks PV string-to-PE resistance is above 50 kΩ; find any short. Check the PE cable. The rest of the checklist is below; work through it in order. Installer only: DC and AC work on a live PV system is dangerous, so owners should note the code and call their installer.
Steps from the source
- Installer checks PV string-to-PE resistance is above 50 kΩ; find any short
- Check the PE cable
- If lower only on rainy days, ISO threshold may be reset in SolarGo (installer)
Source
GoodWe ET / ET Plus+ / BT User Manual EN, Ch.9 Troubleshooting, Ch.9, ISO entryen.goodwe.com ↗
Where installers ask this
- SUN2000 15KTL-M2 low insulation (r/solar)
- reddit.com/r/solar/comments/1lxgtc1/
- reddit.com/r/solar/comments/1ellz9q/
- reddit.com/r/solar/comments/1vktn59/
- reddit.com/r/SolarPakistan/comments/1uhs26h/
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.