Error 203 on a Growatt inverter: PV Isolation Low - insulation problem
Short answer
On a Growatt inverter, Error 203 means: PV Isolation Low - insulation problem. The inverter stops until the fault clears or is reset. The wording differs by model range — each is shown below.
Reviewed 24 September 2026 · 2 sources
What it means
On the MIN 2500-6000TL-X
The manual says: PV Isolation Low - insulation problem.
Part involved: PV array insulation resistance (Riso).
Likely causes:
- PV to ground impedance below 25 kOhm (or 500 kOhm VDE 0126).
- Wet DC breaker.
- Poor panel/inverter earthing.
On the SPH 3000-6000TL BL-UP (48 V battery hybrid)
The manual says: PV Isolation Low.
Part involved: PV array insulation resistance (Riso).
Likely causes:
- PV Isolation Low.
Is it safe?
| Does the inverter stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
The inverter stops until the fault clears or is reset.
Resetting itself: often - the inverter retests insulation at each start, so a moisture-related fault can clear later in the day as the array dries and return next damp morning.
Manual reset: no (clears when insulation test passes).
What you can check
- Read and note the exact code and time from the inverter display or app (screenshot).
- Note whether it only happens in the morning or after rain - tell the installer.
- Check the solar/battery AC isolator and the consumer-unit breaker/RCD are ON (do not reset a breaker that trips again immediately).
- Do not touch panels, DC cables, connectors or the DC isolator.
- Growatt's manual says 'restart inverter'. A homeowner can switch the inverter off and on at its AC isolator/breaker; leave DC switching to the installer unless the manual step says to switch DC off immediately (Error 202).
What the engineer will check
- Insulation-resistance test each string PV+ and PV- to earth (per IEC 62446-1 / BS 7671 Section 712).
- Inspect MC4 connectors, cable damage (rodents/roof edges), water ingress in DC isolators/junction boxes.
- Check module frame earthing.
- Disconnect strings one at a time to find the faulty string.
Who to ask for: PV installer with insulation tester.
Certification: Electrician competent in grid-connected PV (BS 7671 Section 712; IET Code of Practice for Grid-connected Solar PV), ideally the original MCS-certified PV installer; brand-approved/trained installer to keep manufacturer warranty.
What you might notice
Sources
- Growatt MIN 2500-6000TL-X Installation & Operation (User) Manual, general EN 2022-06 ↗ · EN 202206 · page PDF p.22 · Reviewed 24 September 2026
- Growatt SPH 3000-6000TL BL-UP User Manual EN 202512 ↗ · EN 202512 · page PDF p.63 · Reviewed 24 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 24 September 2026