Deye SUN-12K Hybrid Inverter Series Error F24: Deye F24 Grid Relay Failure
Error F24 indicates an internal grid relay self-test failure. During pre-synchronization or disconnection routines, the digital signal processor (DSP) senses an abnormal state across the AC grid safety contactors—such as welded/shorted contacts, open drive coils, or a corrupted voltage feedback signal across the relay bridge.
Hardware Diagnostic Matrix
Spec Ref #e5a6e24cRequired Diagnostic Tools & Instrumentation
Multimeter Probing Targets & Circuit Tolerances
Bench Calibrated ±5%| Test Point / Circuit | Target Nominal Spec | Expected State | Fault Condition |
|---|---|---|---|
| Main Logic DC Bus | 3.3V / 5.0V DC (±0.1V) | Stable DC Potential | <2.9V (Brownout / Sag) |
| Thermistor / NTC Sensor | 10kΩ - 100kΩ @ 25°C | Smooth Thermal Curve | 0Ω (Short) or ∞ (Open) |
| Safety Ground / PE Continuity | < 0.5Ω Resistance | Solid Earth Bond | > 1.0Ω (Floating Chassis) |
Common Symptoms & Fault Manifestations
- Inverter halts grid parallel operation, transitions into fault lockout, and displays 'F24 RelayFault'.
- Audible rapid or metallic chattering from internal electromechanical relays prior to tripping.
- System refuses to export or import power, maintaining off-grid/EPS mode only or disconnecting output entirely.
- Grid indicator LED illuminates solid red or flashes amber while alarm buzzer sounds intermittently.
Root Causes & System Failure Modes
Welded or pitted contacts on the main AC grid isolation relays (typically Hongfa or Omron 40A/50A power relays) caused by grid side switching surges or high inrush currents.
Open circuit or thermal failure on the relay activation coil (nominal 12V or 24V DC coil resistance deviation).
Failed relay low-side driver stage (open/shorted ULN2003A Darlington array or discrete switching N-MOSFETs).
Defective auxiliary relay feedback circuitry, such as burned sensing resistors or degraded optocouplers (e.g., PC817 series) failing to report contact position to DSP.
Severe grid impedance irregularities, micro-arcing on loose AC terminal blocks, or transient overvoltage exceeding contact breakdown ratings.
High-Voltage & Mechanical Safety Isolation
Prior to opening access panels, disconnecting terminals, or probing wiring, perform complete lock-out / tag-out (LOTO). Disconnect all AC mains, DC string isolators, and lithium battery banks. Allow internal smoothing capacitors at least 3 to 5 minutes to dissipate stored residual energy below safe threshold (<30VDC).
Step-by-Step Diagnostic & Resolution Procedure
Safe Isolation & High-Voltage Discharge
Open the Grid AC breaker, Backup/Load breaker, and Generator input breaker. Rotate the DC PV isolator switch to OFF and switch off the battery DC circuit breaker. Wait a minimum of 10 to 15 minutes for the internal DC bus capacitors (rated 500V-800V) to bleed down. Measure with a CAT III 1000V multimeter across PV+, PV-, DC Bus test points, and AC terminals to confirm zero residual voltage (<10V DC/AC) before opening the chassis cover.
Physical & Multimeter Relay Contact Verification
Access the internal AC output filter and relay sub-board. Locate the primary grid relays (three-phase L1, L2, L3, and Neutral relays). With the inverter completely de-energized, set your multimeter to resistance/continuity mode. Measure across the normally open (NO) contact pins of each relay: resistance must read open circuit (OL / >10 MΩ). If any relay pin pair reads continuity (<5 Ω), the contacts are welded shut, confirming a physical hardware failure requiring component replacement.
Coil Integrity and Relay Driver Circuit Diagnostics
Measure the DC resistance across each relay coil terminal (expected nominal value between 150 Ω to 400 Ω depending on relay manufacturer specs). An infinite reading (OL) signifies an open coil winding. If coils are healthy, trace the coil negative drive line back to the driver array (e.g., ULN2003 driver or discrete MOSFET). Using an external benchtop power supply configured to the relay coil rating (12V/24V DC with 300mA current limit), pulse the coil directly to verify crisp mechanical actuation and contact closure (<0.2 Ω across closed switch contacts).
Feedback Optocoupler & Relay Board Repair or Replacement
If contacts and coils pass bench testing, inspect the optocoupler feedback circuit (typically SMD optocouplers adjacent to the relay bank) measuring high-voltage side drop resistors (typically 100kΩ - 470kΩ). Replace any drifted resistors or blown optocouplers. If relays are welded or internally compromised, desolder the damaged relays using a high-thermal-mass desoldering tool, clean flux residue with 99% isopropyl alcohol, and install original-specification replacement relays (rated min. 277VAC / 50A per contact). Alternatively, replace the complete AC relay power module.
Torque Verification, Cold Reboot & Grid Synchronization
Inspect all AC terminal block screws and re-torque to manufacturer specifications (2.5 to 3.0 Nm). Reassemble all covers and interlocks. Re-energize the system strictly in reverse order: Battery first, followed by PV array isolators, allowing the inverter DSP to boot completely. Once stable, close the AC Grid breaker. Monitor the LCD screen or Solarman app during the 60-second countdown self-test to verify error F24 clear and successful contactor engagement into normal on-grid export.
Hardware Reset & Fault Clear Sequence
Controller ProcedurePrevention & Routine Maintenance Guidelines
- Install certified Class II AC Surge Protective Devices (SPDs) upstream in the main service panel to protect internal inverter relays from utility switching surges and lightning transients.
- Verify that the AC feeder cabling is properly sized and that terminal block screw connections are torqued periodically to prevent micro-arcing and excessive contact heating under full 12kW load.
- Maintain the latest official Deye firmware revisions to benefit from optimized zero-crossing switching algorithms that minimize electrical arcing across contacts during connection and disconnection cycles.
Frequently Asked Diagnostic Questions
What does error code F24 indicate on Deye SUN-12K Hybrid Inverter Series?
Error F24 indicates an internal grid relay self-test failure. During pre-synchronization or disconnection routines, the digital signal processor (DSP) senses an abnormal state across the AC grid safety contactors—such as welded/shorted contacts, open drive coils, or a corrupted voltage feedback signal across the relay bridge. In engineering telemetry, it indicates deye f24 grid relay failure requiring circuit verification.
What are the primary triggers causing error F24?
Diagnostic bench telemetry isolates the following common root causes: Welded or pitted contacts on the main AC grid isolation relays (typically Hongfa or Omron 40A/50A power relays) caused by grid side switching surges or high inrush currents.; Open circuit or thermal failure on the relay activation coil (nominal 12V or 24V DC coil resistance deviation).; Failed relay low-side driver stage (open/shorted ULN2003A Darlington array or discrete switching N-MOSFETs).; Defective auxiliary relay feedback circuitry, such as burned sensing resistors or degraded optocouplers (e.g., PC817 series) failing to report contact position to DSP.; Severe grid impedance irregularities, micro-arcing on loose AC terminal blocks, or transient overvoltage exceeding contact breakdown ratings..
How do I reset and clear Deye error F24?
Perform an AC/DC cold reboot: Switch off Grid AC breaker, Load breaker, PV DC isolator, and Battery BMS breaker. Wait 10 minutes until LCD completely turns black and internal capacitors drop below 5V. Turn on Battery breaker, wait for LCD initialization, turn on PV switch, and lastly turn on Grid breaker. Go to Touchscreen > Settings (Gear Icon) > Advanced Settings (enter PIN 0000 or 1234) > Factory Reset or Fault Record > Clear Faults. If the error status repeats immediately after clearing, discontinue clearing and test circuit continuity.
Can I safely resolve error F24 without specialized shop tooling?
This fault is graded as Advanced difficulty with Critical severity. Standard diagnostics require an insulated digital multimeter and appropriate hand tools. Always observe high-voltage isolation procedures.