Growatt 102 Error: PV Insulation Resistance Low
Fix Growatt error 102 (PV isolation fault).
Insulation resistance between the PV DC circuit and Earth Ground is below the safety limit (50 kΩ), indicating a ground fault in the solar array or rooftop wiring.
Probable Causes
Moisture infiltration into rooftop MC4 connectors due to improper crimping or lack of strain relief.
Rodent damage stripping the double insulation layer on DC string wiring in attic spaces.
PV panel junction box cracked or compromised by micro-fractures.
Diagnostic & Testing Steps
- •Red fault LED illuminates steadily; OLED screen displays "Error 102 PV Isolation Low".
- •Solar energy generation stops completely; grid relay remains open.
- •Inverter restarts periodically but aborts connection after initial impedance check.
Tools & Equipment Required
- ✓1000V DC Insulation Resistance TesterTest PV array insulation impedance to ground (normal specification > 50 kΩ).
- ✓CAT III 1000V Digital MultimeterVerify DC voltage balance between MPPT 1 and MPPT 2 input channels.
- ✓MC4 Quick Disconnect ToolUnclip solar string connectors to isolate rooftop moisture ingress.
- ✓Class 0 1000V Insulated GlovesProtection against lethal high-voltage DC electric shock.
- ✓Torx T20 ScrewdriverRemove lower terminal wiring cover and examine DC varistors/SPDs.
Fast Reset Sequence: Solar Inverter Safe AC/DC Shutdown & Reboot Sequence
Before unmounting panels or beginning diagnostic procedures, attempt this manufacturer reset to clear transient microcomputer lockouts:
- 1.Step 1: Switch OFF the dedicated AC circuit breaker at the main electrical distribution panel.
- 2.Step 2: Turn the rotary DC Disconnect Switch on the underside of the inverter to the OFF (0) position.
- 3.Step 3: Wait a minimum of 5 to 10 minutes to allow high-voltage DC capacitors to bleed down to 0V.
- 4.Step 4: Re-engage the DC disconnect first, followed by switching ON the AC breaker.
- 1
Step 1: De-energize DC and AC Connections
[ ] DoneSwitch off AC circuit breaker, turn DC switch to OFF, and wait 10 minutes for internal filter capacitors to discharge.
Verification:Digital display is completely unpowered and capacitor voltage reads 0 VDC. - 2
Step 2: Measure String Isolation Resistance to Ground
[ ] DoneUsing an insulation tester (Megger set to 1000V DC), measure from PV1+ to Ground and PV1- to Ground.
Verification:Healthy string measures > 1.0 MΩ. A reading under 50 kΩ confirms a ground fault on that string. - 3
Step 3: Isolate Defective Module and Reconnect
[ ] DoneSplit string in half on roof to isolate bad module or pinched wire, replace damaged section, and reconnect to inverter.
Verification:Error 102 clears, insulation check passes, and green LED indicates normal power export.
Repair Solutions
Disconnect DC strings and measure resistance between PV+ to Ground and PV- to Ground with a 1,000V insulation tester.
Inspect roof array wiring and elevate cables away from pooling rainwater gutters.
Replace water-damaged MC4 connectors with IP68 rated equivalents.
Frequently Asked Questions
Can I disable the Growatt insulation resistance check?
No. The Riso protection is a mandatory international grid standard (IEC 62109) designed to prevent electrocution and structural rooftop fires.
What is the acceptable minimum isolation reading for a Growatt inverter?
Growatt requires at least 50 kΩ to establish grid connection, though healthy installations should read greater than 10 to 50 MΩ.