Warning What does this mean?

Your system is down or running degraded, but this is not an immediate safety danger. Work through the safe steps below.

Deye Inverter F26 — What a DC Busbar Unbalance Fault Means

F26 means the DC busbar inside your Deye inverter is unbalanced — the internal high-voltage DC rails that feed the power conversion stage are not symmetrical the way they should be. Deye’s documented checks are the internal BUSN cable and the driver-board power cable, followed by a restart — and the internal checks are strictly technician work, since the manual forbids opening the inverter. If a restart does not clear F26, your installer or Deye service needs to take over.

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

Inside your inverter, the DC power from your panels is first boosted onto an internal high-voltage DC busbar — think of it as the inverter’s internal power highway — before being converted to grid-compatible AC. On many designs this bus is split into positive and negative halves that must stay balanced around a midpoint. ‘Unbalanced’ means that symmetry has broken down: one side is riding higher than the other.

The inverter watches this balance continuously, because running the power stage on an unbalanced bus stresses components and distorts the AC output. When the imbalance crosses the trip threshold, F26 stops the show.

Deye’s own troubleshooting is refreshingly specific about where to look first: the BUSN cable (the negative bus connection) and the driver-board power supply cable — internal wiring that can work loose over years of thermal cycling. Everything else on the list is a deeper hardware issue: a failing driver board, degraded bus capacitors, or firmware mismatched to the hardware. On hybrid models, Deye’s documentation adds two external contributors worth knowing about: heavily unbalanced loads across the three phases, and DC leakage current in the system — both of which can push the bus off balance.

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

['A loose internal BUSN cable or driver-board power supply cable — Deye own first check, and a known effect of years of heating and cooling cycles.', 'Severely unbalanced phase loads on three-phase units — Deye hybrid documentation notes that big differences between phase loads can trigger F26.', 'DC leakage current in the system dragging the bus off balance.', 'A failing driver board or degraded DC bus capacitors.', 'Firmware not matched to the hardware revision.']

Safe steps to try

Work top to bottom, ticking off each step as you complete it. 0 of 1 done.

['Restart the inverter once using the documented shutdown/startup sequence and watch whether F26 returns.', 'Note exactly when it appears — at startup, under heavy load, or at random — and whether any large single-phase appliances were running.', 'Photograph the fault screen with the timestamp for your installer.', 'On a three-phase hybrid, note whether the fault coincides with very uneven loading across phases.', 'Do not open the inverter to check the internal cables yourself — Deye manual explicitly prohibits disassembly because of shock hazard; the BUSN and driver-board checks are for qualified personnel with the unit safely isolated.']

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

If F26 comes back after a restart, call your installer or Deye service — that is Deye’s documented next step. Verifying the BUSN cable, the driver-board power cable, and the bus capacitors all require opening the inverter, which only qualified personnel may do after proper isolation and a discharge waiting period. Repeated F26 events point to a hardware fault — typically the driver stage or the DC bus components — that needs professional repair, not repeated restarts.

Frequently asked questions

What is the DC busbar?

It is the inverter’s internal high-voltage DC distribution point — the stage between the panel-side boost circuits and the AC output stage. ‘Busbar’ is just the electrical term for a common conductor that everything connects to.

Can unbalanced house loads really cause F26?

On three-phase hybrid models, yes — Deye’s own hybrid documentation lists large differences between phase loads as a trigger. It is one of the first things the technician will ask about.

Is F26 dangerous?

The inverter has shut itself down, which is the safe state. The danger would be in ignoring the manual’s warning and opening the unit to poke at the busbar — the DC bus holds a charge even after switch-off, which is why only qualified people go in there.

Will a firmware update fix it?

If the cause is firmware mismatched to the hardware, an update performed by the technician can resolve it. But firmware is only one of several possible causes, so it needs proper diagnosis first.

Need a professional?

This fault may need professional diagnosis. Contact a qualified solar electrician in your area.

Sources: meaning and troubleshooting verified against the manufacturer's documentation — Deye SUN-(3-10)K-G03 Grid-tied PV String Inverter User Manual (Ver 2.1, 2021-6), §10.1 Table 10.1 — F26 ‘The DC busbar is unbalanced’ (check BUSN cable / driver board power supply cable; restart; contact installer or Deye service if persistent) (deyeinverter.com)