- Solar and energy
- Solar inverter
18x7F
SolarEdge 18x7F on a solar inverter: residual current surge
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
The inverter detected a residual current (RCD) surge, which SolarEdge links to earth faults from poor insulation. Do not touch the unit: note the code and the time and call a qualified technician.
Safety first
Stop and check this first
- Do not open the inverter or touch DC cables. SolarEdge states an electric shock hazard and that only a qualified technician handles this error.
- A string with an earth fault must not be reconnected to the inverter until a certified installer has repaired it.
Safe checks you can perform
- Code and message on the inverter screen
- Repeat occurrences
- One string at a time test
Leave these tasks to a qualified professional
- Do not attempt this professional task: Identify the string with the earth fault
- Do not attempt this professional task: Insulation test on the affected string
- Do not attempt this professional task: Operating test after repair
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.
Identify the string with the earth fault
What they doThe technician follows the SolarEdge procedure: inverter off, five minute wait, AC and DC disconnected, then strings reconnected one at a time.
They must show youwhich string brings the error back and which do not.
In writingthe string isolated and that it was not reconnected unrepaired.
Insulation test on the affected string
What they doWith an insulation tester they check the string, the home run cables and each optimizer and module pair to find the leaking component.
They must show youthe measured values against the SolarEdge limits.
In writingthe leaking component and the repair done.
Operating test after repair
What they doWith the repaired string reconnected, they start the inverter and check that neither 18x7F nor any isolation error returns.
They must show youthe inverter producing with no error.
In writingthe replaced part and its reference, or the case opened with SolarEdge if nothing was found.
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.
Code and message on the inverter screen
- Who:
- you, with no tools and without opening anything.
- How:
- look at the inverter screen, or SolarEdge monitoring if you have access, and write down the full code.
- Result that matters:
- that it reads 18x7F IRCDMax and whether the inverter has stopped.
- If it shows 18x7F IRCDMax:
- a residual current surge is confirmed; call a qualified technician.
- If it shows 18x3D or 18x3E:
- that is a different earth current error; SolarEdge says to contact its support.
- Evidence to keep:
- photo of the screen with date and time visible.
Evidence: Appendix A: Errors and Troubleshooting (Single Phase Inverter with HD-Wave Technology Installation Guide, MAN-01-250-1.2)
Repeat occurrences
- Who:
- you, with no tools.
- How:
- each time you see the error, note the date, the time and whether the inverter was producing.
- Result that matters:
- whether the error is a one off or keeps returning.
- If it returns on several days:
- it strengthens the case for a permanent earth fault; give the list to the technician.
- If it appeared once:
- keep the record anyway; the technician decides on the string test.
- Evidence to keep:
- list of dates and times of each occurrence.
Evidence: Appendix A: Errors and Troubleshooting (Single Phase Inverter with HD-Wave Technology Installation Guide, MAN-01-250-1.2)
One string at a time test
- Who:
- qualified technician, using the manufacturer precautions.
- How:
- turn the inverter off, wait five minutes for the capacitors to discharge, open the AC breaker and disconnect the DC inputs; then connect each string separately until the error appears.
- Result that matters:
- which string reproduces the error.
- If the error appears with one string:
- that string has the earth fault and stays disconnected until repaired.
- If it does not appear with any single string:
- the technician passes the records to SolarEdge support.
- Evidence to keep:
- report listing the strings tested and the result.
SolarEdge warns of electric shock hazard: do not touch uninsulated wires when the inverter cover is removed. Qualified technician only, with proper precautions.
Evidence: Appendix A: Errors and Troubleshooting (Single Phase Inverter with HD-Wave Technology Installation Guide, MAN-01-250-1.2)
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
- SolarEdge
- Product type
- Solar inverter
Known code variants
- SolarEdge 18x7F
- SolarEdge error 127
- SolarEdge error 18x7F corriente diferencial
- SolarEdge error 18x7F residual current
- SolarEdge IRCDMax
What it means
In the SolarEdge error table, 18x7F IRCDMax (error 127 on firmware 3.18xx and earlier) means the inverter measured a residual current surge. The manufacturer links it to earth faults caused by insufficient insulation to earth in a PV string: modules, DC wiring or optimizers. The official procedure reconnects strings one at a time until the error returns, because the code does not say which string or component is at fault.
Warnings and stop conditions
- Highsource verified
Do not open the inverter or touch DC cables. SolarEdge states an electric shock hazard and that only a qualified technician handles this error.
Evidence: Appendix A: Errors and Troubleshooting (Single Phase Inverter with HD-Wave Technology Installation Guide, MAN-01-250-1.2)
- Mediumsource verified
A string with an earth fault must not be reconnected to the inverter until a certified installer has repaired it.
Evidence: Appendix A: Errors and Troubleshooting (Single Phase Inverter with HD-Wave Technology Installation Guide, MAN-01-250-1.2)
Symptoms and causes
Probable causes · in order
- Earth fault in a PV stringCommon
SolarEdge explains the surge by insufficient insulation to earth. It is confirmed when the error returns with one specific string connected and not with the others.
Evidence: Appendix A: Errors and Troubleshooting (Single Phase Inverter with HD-Wave Technology Installation Guide, MAN-01-250-1.2)
- Module or DC wiring with damaged insulationPossible
Inside the affected string, the leak is usually in a module with defective insulation or in unshielded wiring. It is located with diagnostics or an insulation tester.
Evidence: Isolation Fault Troubleshooting - Application Note, Version 1.4
- Faulty power optimizerPossible
SolarEdge names defective optimizers as a source of earth leakage. It is separated from the module by testing the optimizer alone in the string.
Evidence: Isolation Fault Troubleshooting - Application Note, Version 1.4
- Internal inverter faultPossible
The last source to consider, when no single string reproduces the error. In that case SolarEdge refers the installer to its support.
Evidence: Appendix A: Errors and Troubleshooting (Single Phase Inverter with HD-Wave Technology Installation Guide, MAN-01-250-1.2) · Isolation Fault Troubleshooting - Application Note, Version 1.4
Virtual technician
Does 18x7F 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
SolarEdge Technologies · manual
- 2
Isolation Fault Troubleshooting - Application Note, Version 1.4
SolarEdge Technologies · 2019 · official_doc
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