- Solar and energy
- Solar inverter
PV ISO-PRO
Solis PV ISO-PRO on a solar inverter: low PV insulation
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
The Solis inverter has detected insulation resistance that is too low on the DC side of one or more strings (alarm 1033). Solis says this ground fault must be fixed before the system is energized again: note time and weather and call your installer.
Safety first
Stop and check this first
- PV panels supply DC voltage whenever they are exposed to light. Do not touch panel connectors or cables even when the inverter has stopped.
- Solis states the ground fault must be resolved before the system is energized again, or the inverter can be damaged. Do not keep restarting it.
Safe checks you can perform
- Alarm, suffix and time
- Link with rain and time of day
- One restart with a 5 minute wait
- String by string test
Leave these tasks to a qualified professional
- Do not attempt this professional task: PV+ and PV- voltage to earth per string
- Do not attempt this professional task: Inverter resistance to earth
- Do not attempt this professional task: Enclosure earthing
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
PV+ and PV- voltage to earth per string
What they doWith a multimeter, the installer measures voltage between PV+ and earth and between PV- and earth on every string and watches how the reading changes.
They must show youeach string's readings and how they change, on video if Solis requests it.
In writingwhich string failed and the leak point found.
Inverter resistance to earth
What they doWith the inverter isolated and no strings or AC wires connected, the installer measures resistance between the DC+ and DC- terminals and the heat sink.
They must show youthe measured values against the manufacturer specification.
In writingmeasured values and the conclusion about the inverter.
Enclosure earthing
What they doThe installer checks that the inverter body is connected to earth, which Solis asks to see in photos.
They must show youphotos of the inverter earth connection.
In writingthe state of the earthing and any correction made.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Alarm, suffix and time
- Who:
- you, no tools.
- How:
- open the alarms in the SolisCloud app or, on models with a display, Advanced Information with code 0010 and Alarm Message. Note whether it is PV ISO-PRO01 or PV ISO-PRO02 and the time.
- Result that matters:
- the exact alarm with its suffix and when it first appeared.
- If it appears several times in the history:
- note every date and time for the installer.
- If it appears only once:
- still note it; Solis asks when it first showed up.
- Evidence to keep:
- screenshot of the alarm with date and time.
Evidence: 1033 - PV ISO PRO · How do I get to the alarm messages?
Link with rain and time of day
- Who:
- you, no tools.
- How:
- over several days, note whether the alarm shows all day, only in the morning or evening, or only on rainy or humid days. Solis asks for exactly this information.
- Result that matters:
- whether the alarm follows a weather or time pattern.
- If it only shows with rain or in the morning and clears in good weather:
- it fits a moisture leak or module ageing.
- If it also shows in dry weather:
- it points to a permanent ground fault on a string.
- Evidence to keep:
- daily log of times and weather.
Evidence: User Manual for S6 Series Grid Inverter Version 1.1, Release Date: 04,2024 · 1033 - PV ISO PRO
One restart with a 5 minute wait
- Who:
- you, if you have app access; otherwise the installer.
- How:
- turn the inverter off in Settings with Power OFF, wait 5 minutes and start it with Power ON, as the manual states. Do this once only.
- Result that matters:
- whether the alarm returns after the restart; Solis asks for this result.
- If the alarm returns:
- do not restart again; the ground fault must be fixed before energizing.
- If it does not return:
- note it and watch whether it comes back with humidity.
- Evidence to keep:
- time of the restart and whether the alarm came back.
Evidence: User Manual for S6 Series Grid Inverter Version 1.1, Release Date: 04,2024 · 1033 - PV ISO PRO
String by string test
- Who:
- a qualified PV installer.
- How:
- shut the system down on both DC and AC sides for 5 minutes, remove all strings and connect only one; run it with the grid on for 5 minutes and repeat for each string.
- Result that matters:
- which string makes the alarm appear.
- If one string triggers the alarm:
- the ground fault is on that string; its wires and connections are inspected.
- If none triggers it:
- the installer measures the inverter between DC+ and DC- and the heat sink.
- Evidence to keep:
- table with each string tested and its result.
Removing and connecting strings involves high DC voltage in daylight and arc risk. Qualified installer only.
Evidence: 1033 - PV ISO PRO
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Solar and energy
- Brand
- Solis (Ginlong)
- Product type
- Solar inverter
Known code variants
- Solis alarm 1033
- Solis alarma 1033
- Solis PV ISO-PRO
- Solis PV ISO-PRO01
- Solis PV ISO-PRO02
What it means
Solis defines PV ISO-PRO as resistance on the DC (solar) side that is too low on one or more strings, that is, a ground fault. Its service team lists wire connections, damaged insulation, DC wires pinched under the array, wires landed in the wrong terminals and rain triggering the leak. The S6 manual adds that if it only appears on rainy days or at a certain time in the morning, module ageing can raise leakage current. The code does not say which string or point fails, and on its own it does not prove the inverter is faulty.
Warnings and stop conditions
- Higheditorial warning
PV panels supply DC voltage whenever they are exposed to light. Do not touch panel connectors or cables even when the inverter has stopped.
Evidence: User Manual for S6 Series Grid Inverter Version 1.1, Release Date: 04,2024
- Highsource verified
Solis states the ground fault must be resolved before the system is energized again, or the inverter can be damaged. Do not keep restarting it.
Evidence: 1033 - PV ISO PRO
Symptoms and causes
Probable causes · in order
- Ground fault in a string's wiringPossible
Damaged connections or insulation on one string's cables. It is confirmed when the alarm only appears with that string connected during the string by string test.
Evidence: 1033 - PV ISO PRO
- Pinched wires or wrong terminalsPossible
Solis lists DC wires pinched under the array and wires landed in the wrong terminals. They are found by physically inspecting the string that triggers the alarm.
Evidence: 1033 - PV ISO PRO
- Water or humidity causing the leakPossible
Rain can trigger a ground fault. You can tell because the alarm appears on damp days and clears when the weather improves.
Evidence: User Manual for S6 Series Grid Inverter Version 1.1, Release Date: 04,2024 · 1033 - PV ISO PRO
- Module ageingPossible
According to the S6 manual, if the error only appears with rain or at a certain time in the morning, ageing modules can make leakage current too high.
Evidence: User Manual for S6 Series Grid Inverter Version 1.1, Release Date: 04,2024
Virtual technician
Does PV ISO-PRO still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
User Manual for S6 Series Grid Inverter Version 1.1, Release Date: 04,2024
Ginlong (Ningbo) Technologies Co., Ltd. (Solis) · 2024 · manual
- 2
Ginlong (Ningbo) Technologies Co., Ltd. (Solis Service Center) · 2025 · official_doc
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