- Solar and energy
- Solar inverter
203
Growatt 203 on a solar inverter: low PV insulation to earth
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
The Growatt inverter measured insulation between the PV side and earth that is too low (PV Isolation Low) and is not feeding in. Note the code, time and weather, and call your installer. Do not touch panel connectors or cables.
Safety first
Stop and check this first
- A 203 on its own does not prove the inverter is faulty. Growatt treats it as a system fault: insist on the insulation measurement before accepting an inverter replacement.
- Do not unplug panel connectors or operate the DC switch to test. Growatt forbids disconnecting DC connectors under load and limits wiring work to qualified personnel.
Safe checks you can perform
- Exact code on the display
- Weather and time-of-day log
- Information Growatt asks for
- PV array insulation measurement
Leave these tasks to a qualified professional
- Do not attempt this professional task: Insulation test of each string to earth
- Do not attempt this professional task: Earthing and DC breaker inspection
- Do not attempt this professional task: Module wiring check and fault history
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.
Insulation test of each string to earth
What they doThe installer measures the impedance of PV(+) and PV(-) to earth for each string with the array disconnected from the inverter.
They must show youthe measured value for each pole and string against Growatt's 25 kΩ or 500 kΩ minimum.
In writingthe values, the affected string and the repair done.
Earthing and DC breaker inspection
What they doChecks earth continuity of the panel mounting and the inverter, and whether the DC breaker has water or moisture inside.
They must show youphotos of the DC breaker interior and the earth continuity test.
In writingwhat was found and what was dried, sealed or replaced.
Module wiring check and fault history
What they doVerifies that no module DC pole is grounded and reviews in the inverter or app when the fault repeats.
They must show youthe module wiring diagram and the fault history.
In writingthe cause found and a successful start-up after the repair.
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.
Exact code on the display
- Who:
- you, no tools.
- How:
- read the inverter OLED screen or the monitoring app and write down the full text, for example PV Isolation Low or Error: 203.
- Result that matters:
- confirming the alert is 203 and not another code from Growatt's table.
- If it shows PV Isolation Low or Error:
- 203: move on to logging when it appears.
- If it shows another code:
- look up that code; this page does not apply.
- Evidence to keep:
- photo of the screen with the code, serial number and model.
Evidence: Installation & Operation Manual MIN 2500TL-X MIN 3000TL-X MIN 3600TL-X MIN 4200TL-X MIN 4600TL-X MIN 5000TL-X MIN 6000TL-X (GR-UM-155-A-04) · Installation & Operation Manual MIC 600TL-X to MIC 3300TL-X (MIC_600-3300TL-X EN 202309)
Weather and time-of-day log
- Who:
- you, without touching the equipment.
- How:
- note the date, time and whether there was rain, dew or fog when the code appeared, over several days.
- Result that matters:
- whether the fault only shows in damp conditions or also in dry weather.
- If it only appears when damp and clears when dry:
- points to water in the DC breaker or connectors.
- If it also appears in dry, sunny weather:
- points to a permanent insulation defect.
- Evidence to keep:
- list of dates, times and conditions; Growatt asks for ambient conditions when you contact them.
Evidence: Installation & Operation Manual MIN 2500TL-X MIN 3000TL-X MIN 3600TL-X MIN 4200TL-X MIN 4600TL-X MIN 5000TL-X MIN 6000TL-X (GR-UM-155-A-04) · Installation & Operation Manual MIC 600TL-X to MIC 3300TL-X (MIC_600-3300TL-X EN 202309)
Information Growatt asks for
- Who:
- you, with the installation paperwork.
- How:
- collect serial number, model, error message, whether it happened before, and panel make, model and number per string.
- Result that matters:
- having what the manual lists for Growatt service.
- If you have everything:
- give it to the installer so they can open a case.
- If panel data is missing:
- ask the installer; it is in the installation documents.
- Evidence to keep:
- one document with that data plus the screen photos.
Evidence: Installation & Operation Manual MIN 2500TL-X MIN 3000TL-X MIN 3600TL-X MIN 4200TL-X MIN 4600TL-X MIN 5000TL-X MIN 6000TL-X (GR-UM-155-A-04) · Installation & Operation Manual MIC 600TL-X to MIC 3300TL-X (MIC_600-3300TL-X EN 202309)
PV array insulation measurement
- Who:
- qualified PV installer.
- How:
- with the system disconnected as the manual describes, check frame and inverter earthing, moisture in the DC breaker and impedance of PV(+) and PV(-) to earth.
- Result that matters:
- each pole's impedance to earth against Growatt's minimum: more than 25 kΩ, or 500 kΩ under VDE 0126.
- If any string is below it:
- locate the leak on that string before reconnecting.
- If everything passes and the error remains:
- Growatt says to contact its service.
- Evidence to keep:
- report with the measured value per string and pole, and the standard applied.
The DC side carries dangerous voltage in daylight and connectors must not be disconnected under load. Only a qualified installer measures or handles strings, the DC switch or earthing.
Evidence: Installation & Operation Manual MIN 2500TL-X MIN 3000TL-X MIN 3600TL-X MIN 4200TL-X MIN 4600TL-X MIN 5000TL-X MIN 6000TL-X (GR-UM-155-A-04) · Installation & Operation Manual MIC 600TL-X to MIC 3300TL-X (MIC_600-3300TL-X EN 202309)
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
- Growatt
- Product type
- Solar inverter
Known code variants
- 203 Información no autoritativa
- 203 Informations non officielles
- 203 Informazioni non autorevoli
- 203 Nicht autoritative Informationen
- 203 Non-Authoritative Information
- código 203 Epson
- EcoTank 203 fax
- Epson 203
- Epson cannot detect the dial tone
- Epson error code 203
- Epson ET-5800 203
- Epson ET-5850 203
- Epson fax no dial tone
- Epson fax sin tono de marcado
- Epson L6550 203
- Epson no detecta tono de marcación
- Growatt 203 aislamiento FV bajo
- Growatt error 203
- Growatt Error: 203
- Growatt isolation fault
- Growatt PV Isolation Low
- HTTP 203
- HTTP status 203
What it means
Growatt lists Error 203 as a system fault, caused mainly by the installation rather than the inverter. Before connecting, the unit checks the impedance of PV(+) and PV(-) to earth. The manual asks to check earthing of the panel frames, earthing of the inverter, whether the DC breaker got wet, and the PV impedance to earth. Modules with a grounded DC circuit also trigger it. The code does not say which string or point is at fault.
Warnings and stop conditions
- Mediumeditorial warning
A 203 on its own does not prove the inverter is faulty. Growatt treats it as a system fault: insist on the insulation measurement before accepting an inverter replacement.
Evidence: Installation & Operation Manual MIN 2500TL-X MIN 3000TL-X MIN 3600TL-X MIN 4200TL-X MIN 4600TL-X MIN 5000TL-X MIN 6000TL-X (GR-UM-155-A-04) · Installation & Operation Manual MIC 600TL-X to MIC 3300TL-X (MIC_600-3300TL-X EN 202309)
- Highsource verified
Do not unplug panel connectors or operate the DC switch to test. Growatt forbids disconnecting DC connectors under load and limits wiring work to qualified personnel.
Evidence: Installation & Operation Manual MIN 2500TL-X MIN 3000TL-X MIN 3600TL-X MIN 4200TL-X MIN 4600TL-X MIN 5000TL-X MIN 6000TL-X (GR-UM-155-A-04) · Installation & Operation Manual MIC 600TL-X to MIC 3300TL-X (MIC_600-3300TL-X EN 202309)
Symptoms and causes
Probable causes · in order
- Moisture in the DC breakerPossible
Growatt asks to check whether the DC breaker got wet. This fits when the code appears after rain or dew and clears once everything dries.
Evidence: Installation & Operation Manual MIN 2500TL-X MIN 3000TL-X MIN 3600TL-X MIN 4200TL-X MIN 4600TL-X MIN 5000TL-X MIN 6000TL-X (GR-UM-155-A-04) · Installation & Operation Manual MIC 600TL-X to MIC 3300TL-X (MIC_600-3300TL-X EN 202309)
- Damaged insulation on PV strings or cablingPossible
If the impedance of PV(+) or PV(-) to earth is below Growatt's minimum, there is leakage in panels, connectors or cables. Only a per-string measurement confirms it.
Evidence: Installation & Operation Manual MIN 2500TL-X MIN 3000TL-X MIN 3600TL-X MIN 4200TL-X MIN 4600TL-X MIN 5000TL-X MIN 6000TL-X (GR-UM-155-A-04) · Installation & Operation Manual MIC 600TL-X to MIC 3300TL-X (MIC_600-3300TL-X EN 202309)
- Poor earthing of frames or inverterPossible
The manual asks to check earthing of the panel mounting and of the inverter. A loose or missing earth makes the insulation check fail.
Evidence: Installation & Operation Manual MIN 2500TL-X MIN 3000TL-X MIN 3600TL-X MIN 4200TL-X MIN 4600TL-X MIN 5000TL-X MIN 6000TL-X (GR-UM-155-A-04) · Installation & Operation Manual MIC 600TL-X to MIC 3300TL-X (MIC_600-3300TL-X EN 202309)
- Modules with the DC circuit groundedPossible
The MIC TL-X has no galvanic isolation. Growatt states that connecting modules with a grounded DC pole gives the PV ISO Low message. Usually seen from commissioning.
Evidence: Installation & Operation Manual MIC 600TL-X to MIC 3300TL-X (MIC_600-3300TL-X EN 202309)
Virtual technician
Does 203 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
Shenzhen Growatt New Energy Co., Ltd · 2022 · manual
- 2
Installation & Operation Manual MIC 600TL-X to MIC 3300TL-X (MIC_600-3300TL-X EN 202309)
Shenzhen Growatt New Energy Co., Ltd · 2023 · manual
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