GoodWe Error 15 — PV Overvoltage (string voltage too high)

⚠ DANGER — this fault involves lethal voltage. Do not attempt a DIY fix. Call a qualified technician.

What it means: The total open-circuit voltage of one of your PV strings is higher than the maximum DC input voltage the inverter is built to withstand. Too many panels are wired in series. This is a design fault, not a wear fault — the array is delivering a voltage the inverter's DC side is not rated for, and every hour it stays that way is an hour of stress on components that were never specified for it.

Why does GoodWe show 15?

• Too many panels connected in series in one string
• String sized from a warm-afternoon voltage reading instead of the panel's temperature coefficient
• Extra panels added later by a second crew without re-checking the string voltage
• A string re-terminated during maintenance and reconnected into the wrong configuration

The Pakistan factor

PV over-voltage season in Pakistan is January, not July. Panel open-circuit voltage rises as cell temperature falls, so a string that a crew sized against a 45 C afternoon reading in Lahore in June can go over the inverter's limit on the first clear cold morning in Quetta, Murree, Skardu or upper Punjab. That is why this fault so often shows up months after commissioning and looks like the inverter failing at exactly the wrong time. The second local driver is the panel that got added later. Systems here are expanded in stages, often by a different crew than the one that designed the string, and two extra modules dropped into an existing series run is enough to cross the limit. If anyone offers to make the alarm go away without changing the string, get someone else.

How to fix it

1. Switch the inverter's DC switch to OFF and leave it off. Then stop. There is no safe homeowner step beyond this one.
2. Understand why. A PV array is live whenever there is daylight and it cannot be switched off at the panel — the string sits at its open-circuit voltage all the way down the roof cable. On a GoodWe hybrid that ceiling is high, 600 V DC on an ES Uniq single-phase unit and 1000 V DC on an ET three-phase unit. Do not go on the roof, do not pull a DC connector, and do not "just remove one panel" to see if it clears.
3. Call your installer and tell them the code is 15. GoodWe's procedure from here is theirs, not yours — measure the DC voltage of each string with a multimeter and compare it against the inverter's maximum DC input voltage.
4. The installer's fix is to reduce the number of panels in the affected string so the open-circuit voltage sits inside the inverter's limit, and to size it using the panel's temperature coefficient rather than a reading taken on a warm day. GoodWe directs installers to their EZ Designer tool for exactly this calculation.
5. If the string measures within range and 15 still fires, it goes to the GoodWe service centre. Do not re-energise a string that has been measured over the limit while you wait.