Sunsynk F24: DC Insulation Impedance Failure
F24 means your Sunsynk measured low insulation resistance on the DC (solar panel) side, which is to say a possible ground fault. It is a safety check: if current could leak to earth, the inverter stops. A brief F24 in damp weather is often moisture; a stubborn one points to a real insulation problem that needs inspection.
What usually causes F24
- Moisture or condensation in a DC connector, junction box or cable gland, common early morning or after rain.
- Damaged or aged cable insulation letting current leak toward ground.
- A grounding (PE) problem in the array or system earth.
- A faulty panel or junction with degraded insulation.
What to do, safely
Inspection is for the pros Working on DC wiring and grounding is an installer job, and PV strings are live in daylight. Your safe role is to note the pattern and let it self-clear once.
- Note the pattern. Does F24 mainly show in the morning, after rain or in humid weather, then clear as things dry? That points to moisture and is common.
- Let it self-clear or power-cycle once. AC off, then the DC isolator, wait five minutes, restart. A moisture-driven F24 often clears as the day warms.
- If it persists, especially in dry weather, stop. A steady F24 is a genuine insulation or grounding fault. Don't keep resetting it.
- Call your installer. They measure the insulation resistance, find the wet or damaged point, and fix it.
Quick decision flowchart
F24 appears
↓ does it clear as it dries, mostly in damp conditions?
✅ Yes → likely moisture. Keep an eye on it and mention it at the next service.
❌ No, persists or shows in dry weather → real insulation / ground fault.
↓
Persistent F24 needs an installer to measure insulation resistance and inspect the DC wiring and grounding.
When to bring in a professional
Insulation faults are a safety matter (leakage to ground). A persistent or dry-weather F24 should be inspected by a licensed installer, not cleared and ignored.
Related Sunsynk codes
FAQ
F24 shows every morning then clears. Is it serious?
That pattern usually means overnight moisture on the DC wiring that dries off. Worth reporting at your next service, but a brief morning F24 that clears is commonly moisture rather than a failing part.
Can I fix the moisture myself?
No. Locating and sealing a damp or damaged DC connection is qualified work on live DC wiring. Note the pattern and have your installer handle it.
Sources
- Sunsynk Hybrid Inverter User Manual (F24 = DC insulation impedance failure; check PV panel connections and inverter PE cable grounding).
- Sunsynk fault-code references and installer documentation.
⚠️ Safety disclaimer. A DC insulation fault is an electrical-safety issue. PV wiring is live in daylight. This guide covers noting the pattern and a single safe power cycle only. Inspection and repair must be done by a licensed installer or electrician.