Insulation Error

What does 204 mean?

This status code indicates that the insulation resistance of the solar module strings connected to the Fronius Primo GEN24 208-240 inverter is too low. This is a critical safety issue, often caused by moisture ingress or physical damage to the solar modules or DC cabling, compromising electrical isolation.

• Moisture ingress into the solar modules or their junction boxes.
• Damage to the insulation of the solar modules, such as cracks or delamination.
• Damage to the insulation of the DC cabling (PV+ or PV-) due to mechanical stress, UV degradation, or animal damage.

Click steps to track your progress.

1. 1

   Measure the insulation resistance of the solar module strings between PV+ to ground (GND) and PV- to ground (GND) using a megohmmeter (e.g., at 500VDC). Expect values >1 MΩ.

2. 2

   Inspect all DC cabling for visible signs of damage, cuts, abrasions, or signs of moisture ingress.

3. 3

   Examine solar modules for physical damage to the backsheet, frame, or glass that could compromise insulation.

4. 4

   De-energize the inverter (switch off AC and DC disconnects), wait for 5 minutes, then re-energize to reset. If the message persists, the inverter may require service.