Deye F55: DC Bus Voltage Too High
F55 means the inverter's internal DC bus voltage climbed above its safe limit. A common real-world cause is the solar string voltage running high, which happens most on cold, bright mornings when panels produce a higher voltage. The inverter stops to protect itself.
What usually causes F55
- High PV string voltage, especially in cold weather, when panel open-circuit voltage rises.
- Too many panels in a string for the inverter's input window (a design issue if it happens often).
- A transient spike that a restart clears.
The safe fix, step by step
- Power-cycle safely. Turn off the AC breaker, then the DC isolator, wait 5 minutes, then restart. A transient F55 often clears.
- Note the conditions. Does it happen mainly on cold, sunny mornings? That points to PV voltage, and it may ease as the day warms.
- If F55 keeps returning, especially repeatedly, the string design (panels per string) may be too high for the inverter. That's for your installer to check.
When to call a professional
Repeated F55 can mean the PV array voltage is regularly exceeding the inverter's input limit, which your installer needs to review (string sizing). Don't keep resetting it if it returns often.
Related Deye codes
FAQ
Why would cold weather cause F55?
Solar panels produce a higher voltage when they're cold. On a freezing, sunny morning the string voltage can spike above the inverter's limit, triggering F55 until the panels warm up.
It only happens occasionally. Is that fine?
An occasional, weather-driven F55 that clears is usually manageable, but if it's regular, have your installer confirm the string sizing is within the inverter's input range.
Sources
- Deye Hybrid Inverter User Manual (F55 = "DC bus voltage too high"; power-cycle, technician if it returns).
- Deye dealer technical references for DC-side codes.
⚠️ Safety disclaimer. Solar inverters carry lethal DC and AC voltage even when "off", and PV inputs are live in daylight. This guide covers a single safe power cycle only. String sizing and DC wiring must be reviewed by a licensed installer.