Fox ESS PV Volt Fault
PV Volt Fault (often shown as Error 17) means the DC voltage coming from one of your solar strings is outside the range the inverter accepts, so it stops to protect itself. On an H1 G2, for example, each MPPT input is rated to a maximum of 580V DC. A reading that climbs near that ceiling, or one that sits far too low, both trip this fault. Most often it points to how the string was designed rather than a fault inside the inverter.
What usually causes it
- Cold, sunny mornings push the voltage too high. On a crisp winter morning, panel open-circuit voltage rises with the cold, and a long string can briefly exceed the inverter limit (580V DC per MPPT on an H1 G2 example).
- Too many panels in series. A string with one panel too many sits close to the ceiling and tips over the limit on the coldest days.
- A very low reading instead. An unusually low PV voltage suggests a string-design problem or a poor connection, such as too few panels in series or a loose DC plug.
- A faulty or shaded panel dragging the string voltage out of its expected window.
How to handle it safely
- Open FoxCloud and read PV1 and PV2 voltage. Note what each MPPT input is showing when the fault appears, ideally on a cold, bright morning when it is most likely.
- Compare it to the limit. If a reading sits near the 580V ceiling (H1 G2 example), the string is likely one panel too long for cold conditions. If it sits far too low, the string may be too short or have a connection problem.
- Do not keep resetting. If the fault returns on cold mornings, repeated restarts will not fix it. This is a design issue, not something a reset clears.
- Contact your installer to confirm the string configuration. The fix is usually a wiring change, such as removing one panel from the series string, and that is installer work, not an owner task.
Quick decision flowchart
Related Fox ESS codes
FAQ
Why does PV Volt Fault only show up on cold, sunny mornings?
Solar panels produce a higher open-circuit voltage when they are cold. On a crisp, bright winter morning a long string can briefly climb above the inverter limit (580V DC per MPPT on an H1 G2), so the inverter stops to protect itself. As the panels warm through the day the voltage drops back, which is why it often clears on its own but returns on the next cold morning.
Can I just keep restarting the inverter to clear it?
Restarting may clear it for that moment, but if the cause is a string that is too long, the fault will come back on the next cold morning. This is normally an installer design fix, not a repeated reset. Check PV1 and PV2 voltage in FoxCloud, and if a reading sits near the limit, ask your installer to confirm the string configuration.
Helpful guides
Sources
- Fox ESS H1 G2 inverter datasheet and user manual (maximum PV input voltage of 580V DC per MPPT; PV Volt / Error 17 = string voltage out of range).
- FoxCloud monitoring alarm list and installer guidance on PV string design and per-MPPT voltage limits.