Sunsynk F20: DC Overcurrent Fault (Hardware)
F20 is the DC-side twin of F18. Your Sunsynk sensed too much current coming in on the DC side (the solar panels and battery) and shut down to protect the hardware. The usual triggers are a wiring issue on the PV or battery input, or, in off-grid mode, asking for more power than the system can deliver at once.
Panels, battery, or load?
- A PV or battery connection problem, such as a loose, wrong or reversed DC connection.
- Too much demand in off-grid mode, where the load pulls more than the battery and inverter can supply, spiking the DC current.
- A one-off surge the protection caught.
- Rarely, an internal hardware fault, only likely if F20 keeps returning with everything correct.
How to clear it safely
Hands off the DC terminals Checking whether something changed and reducing load are safe. Physical DC wiring work is for your installer, and PV inputs are live in daylight.
- Reduce the load (off-grid). If you are running on battery, switch off heavy appliances so the system isn't pushed past its limit.
- Think about recent changes. Did F20 begin after new panels, a new battery or wiring work? That points to a connection issue from then.
- Power-cycle safely. AC breaker off, then the DC isolator, wait five minutes, then restart both.
- Watch what happens. If F20 clears and stays gone with a sensible load, you are good. If it returns, stop and get the DC connections checked.
When to bring in a professional
If F20 returns after a clean restart, or you suspect a reversed or loose DC connection, that is an installer job. Don't keep resetting a returning DC overcurrent fault.
Related Sunsynk codes
FAQ
F20 trips when I switch on a big appliance off-grid.
That is a classic overload trigger. A high-draw appliance spikes the DC current beyond the limit. Stagger heavy loads, or confirm your demand is within the inverter and battery rating.
Could it mean my panels are wired wrong?
If F20 started right after install or panel work, a reversed or loose DC connection is possible. Don't probe the DC wiring yourself; have the installer verify polarity and connections.
Sources
- Sunsynk Hybrid Inverter User Manual (F20 = DC over current, hardware; check PV/battery connections, reduce load for off-grid startup).
- Sunsynk fault-code references and installer documentation.
⚠️ Safety disclaimer. Solar inverters carry lethal DC and AC voltage even when "off", and PV inputs are live in daylight. This guide covers reducing load and a single safe power cycle only. DC wiring checks must be done by a licensed installer or electrician.