# Fronius state 475 insulation error: what it means and what to do

Fronius state 475 means the inverter's automatic insulation measurement found too low a resistance between the solar array and ground, so it stops feeding power to the grid. Code 502 is the warning version of the same problem, shown while the inverter keeps running. Fronius says there may be a problem with the panels or their cabling and that it often happens only in certain conditions such as rain; its advice is to contact your installer.

## Common causes

- A problem with the solar panels or their cabling, creating a connection between the solar circuit and ground.
- Poorly insulated DC cables or faulty panels, which Fronius gives as examples of a short to ground.
- Moisture: Fronius notes the error often occurs only under certain conditions, such as rain.

## Safe steps to try

1. **Keep clear of the system** Do not open the inverter, a disconnect, a junction box or any conduit, and do not touch the panels, racking or wiring.
2. **Note the code and the weather** Write down whether you see 475 or 502 and whether it appeared during or after rain. That detail helps the technician find the fault.
3. **Contact your installer or a technician** This is Fronius's instruction for both codes. Finding an insulation fault needs test equipment and a qualified technician.

## When to call a professional

Call promptly for 475, and also for 502 if it keeps coming back. Both mean the insulation between the solar wiring and ground is too low somewhere.

## Frequently asked questions

### What is the difference between 475 and 502?

Fronius lists 475 as an insulation error that stops the inverter feeding power to the grid, and 502 as a warning shown on the display while the inverter keeps operating. Both point to the same kind of problem.

### It cleared after the rain stopped. Is it fixed?

Probably not. Fronius notes this error often appears only in certain conditions such as rain, so a code that clears when things dry out usually means a weak spot is still there.

Canonical page: https://otovo.com/repair/fronius/475