Critical What does this mean?

A safety-rated fault — there may be a risk of electric shock, fire, or equipment damage. Do not try to fix this yourself. Call a qualified electrician.

Deye Inverter F20 — DC Overcurrent Fault, Causes and Safe Fixes

F20 is a hardware-level DC overcurrent fault: your Deye inverter measured more current on the DC side than its power stage can safely handle, and shut down to protect itself. It most often appears when a hybrid inverter starts a large load in off-grid mode, or when a PV or battery connection is faulty. Reduce the connected load and restart via the DC and AC switches — if F20 keeps returning, call your installer.

What should I do first?

Two quick questions — we'll point you to the right starting point.

Is this code still showing on your inverter's display?

What this code means

F20 means the inverter's hardware DC overcurrent protection has tripped. The "DC side" is everything feeding the inverter with direct current: your solar panel strings and, on hybrid models, the battery. When the current on that side exceeds a hard-wired safety threshold, the inverter stops inverting immediately. That shutdown is the protection working as designed — sustained overcurrent would overheat and destroy the power electronics.

Deye distinguishes software and hardware current trips. F20 is the hardware one (internal name Tz_Dc_OverCurr_Fault), which makes it the more serious of the DC-side current faults: it indicates current actually reached the hardware limit, not just a firmware estimate. Its AC-side sibling is F18 (AC overcurrent of hardware); F20 is the DC-side equivalent.

The single most common trigger is specific to hybrid inverters running off-grid. When the grid is down and the inverter starts up a large load — a water pump, air conditioner, or kettle — the startup surge can briefly demand far more DC current than steady running needs, and the hardware protection trips. Deye's own documentation calls out exactly this scenario: in off-grid mode, starting with a big power load may report F20, and the remedy is to reduce the connected load.

Other triggers sit on the input side. A loose, corroded, or damaged PV or battery connection can cause current spikes; a string delivering current outside the allowed range points to a wiring or panel problem; and in rarer cases the fault comes from inside the unit — a firmware version mismatched to the hardware, or a failing DC current sensor and its detection circuit. Those internal causes are strictly installer territory: diagnosing them requires opening the inverter and measuring live circuits.

What is this downtime costing you?

Rough estimate while your system isn't producing. Adjust the numbers to match your setup.

System size (kW) Peak sun hours / day Electricity rate ($/kWh)

–per day

–per week

–per 30 days

≈ – kWh of lost production per day.

Estimate only — assumes ~80% real-world output vs. nameplate. Actual losses depend on weather, shading, panel direction, and your tariff.

Common causes

Starting a large backup load while the inverter is in off-grid mode — the motor or heater inrush trips the hardware DC protection. This is the scenario Deye documents explicitly.
A loose, corroded, or damaged PV or battery connection causing unstable, spiking DC current.
A PV string delivering current outside the allowed range — for example after panels were added, restringing work, or a developing panel fault.
A firmware version that does not match the installed hardware, confusing the protection thresholds.
A faulty DC current sensor or its detection circuit on the control board — an internal fault only an installer can diagnose.

Safe steps to try

Work top to bottom, ticking off each step as you complete it. 0 of 5 done.

Write down the exact code (F20), the time it appeared, and whether the grid was up or down — off-grid F20s point at load inrush.
If you were off-grid, switch off or unplug large loads (kettles, pumps, air conditioners, heaters) before doing anything else.
Turn the DC switch OFF and the AC switch (or breaker) OFF, wait one full minute, then switch the AC back on followed by the DC switch.
Check that the total load on the backup circuit is within the inverter's rated output, and move non-essential loads off the backup side if it is close to the limit.
Do not open the inverter and do not touch any DC wiring or battery terminals — DC remains dangerous even with the unit switched off.

Is your inverter still under warranty?

Before paying for a repair, check — your installer may fix this free.

Brand Year installed

Based on typical standard warranty terms — always confirm with your warranty card or installer paperwork, as terms vary by model, region, and purchase date.

When to call an electrician

Call your installer if F20 persists after a restart with the load reduced. Anything beyond that point — checking the DC current sensor and its detection circuit, verifying the firmware matches the hardware, or inspecting PV and battery connections for damage — requires opening the inverter and working around live DC, which is professional-only work.

If you notice a burning smell, smoke, or scorch marks around the inverter, battery, or DC isolators, switch the system off using the DC and AC switches and call a professional immediately. Do not keep restarting into a recurring F20: repeated hardware-level trips stress the power stage.

Frequently asked questions

Is F20 dangerous?

The inverter shut itself down to prevent damage, so the protection did its job. The danger lies in ignoring a recurring F20 — repeated hardware overcurrent trips can degrade the power electronics, and the underlying cause (a bad connection or overloaded startup) needs fixing.

What is the difference between F20 and F18?

F18 is the AC-side hardware overcurrent fault; F20 is the DC-side equivalent (PV and battery side). They protect different parts of the inverter and point at different checks — F20 means looking at DC inputs and off-grid loads, not the AC output.

Why does F20 only appear when the grid is down?

In off-grid mode the inverter alone must supply every startup surge. A motor or compressor starting can briefly demand several times its running current, spiking DC current past the hardware limit. On-grid, the grid absorbs those surges.

Can I clear F20 by restarting the inverter?

One restart after reducing the load is the documented homeowner step. If the fault trips again immediately, further restarts will not fix it — something needs professional measurement, so call your installer.

Need a professional?

This fault is a safety risk — do not attempt to fix it yourself. Contact a qualified solar electrician in your area.

Sources: meaning and troubleshooting verified against the manufacturer's documentation — Deye SUN-(3-10)K-G03 and SUN-(40-50K-G-LV) String Inverter User Manuals (deyeinverter.com) — Error code table: F20 'DC over current fault of the hardware'. Also documented in the Deye SUN-5K-SG01HP3-EU-AM2 Hybrid Inverter User Manual fault table as F20 Tz_Dc_OverCurr_Fault, with the off-grid big-load note.