Did you know that 80% of all solar system fires are caused by "Arc Faults"? And the only device that can prevent them is the AFCI. This article explains AFCI 3.0, the latest generation that uses AI to detect arc faults, in detail.
Warning: Solar Fires Increase Every Year
An NFPA report (USA) states that there have been 3,500+ house fires caused by solar systems over the past 10 years, with 80% caused by arc faults in DC wiring - which can be prevented with an AFCI.
Table of Contents
1. What Is AFCI
AFCI (Arc Fault Circuit Interrupter) is a system that detects and disconnects arc faults in the DC wiring of a solar system. It operates within milliseconds when a spark is detected, before enough heat builds up to ignite a fire.
The AFCI is located inside the inverter or installed as a separate (external) device, but most newer models are built into the inverter for convenience.
2. What Is an Arc Fault and What Causes It
An arc fault is a spark that occurs in a DC string when there is a problem with the wiring. It resembles a tiny lightning strike, but it is continuous and reaches up to 10,000°C (hot enough to melt or ignite anything).
Causes of Arc Faults
- Series Arc Fault: A broken or loose wire causes current to jump across the gap.
- Parallel Arc Fault: Damaged wire insulation causes wires to short together.
- Ground Arc Fault: A wire shorts to ground or to the steel mounting frame.
Common Causes in Thailand
- Rodents chewing wires - very common in homes with gaps in the roof
- Poor DC wiring installation - loose MC4 connectors
- Old wiring / degraded insulation - UV causes insulation to crack
- Wires rubbing against the steel frame - wearing through over the long term
- Insects / bird nests - causing moisture in the wiring
3. How AFCI Works
Step 1: Signal Detection
The AFCI continuously captures the electrical signal in the DC string (high sample rate of 100,000+ times per second).
Step 2: Pattern Analysis
It compares the signal against known arc fault patterns - an arc fault produces high-frequency noise (1-100kHz) that differs from the inverter's normal operation.
Step 3: Verification and Decision
If a pattern matches a real arc fault (not a false noise), the system disconnects the DC immediately within 100ms.
Step 4: Alert
It sends an alarm signal to the app + cloud monitoring to notify the homeowner immediately.
4. AFCI 1.0 vs 2.0 vs 3.0
| Topic | AFCI 1.0 | AFCI 2.0 | AFCI 3.0 |
|---|---|---|---|
| Year introduced | 2010 | 2016 | 2023+ |
| Detection method | Rule-based | Improved Algorithm | AI-driven (Machine Learning) |
| False alarm rate | 10-20% | 3-5% | <0.5% |
| Detection speed | 200-500ms | 100-200ms | <100ms |
| Series Arc protection | ✓ | ✓ | ✓ |
| Parallel Arc protection | ✗ | ✓ | ✓ |
| Self-learning | ✗ | ✗ | ✓ |
| Cloud-based update | ✗ | Partial | Full OTA update |
5. GoodWe's AI-driven AFCI 3.0
GoodWe is the first inverter manufacturer to make AFCI 3.0 a built-in standard across all models, using:
- Machine Learning Model - trained on a dataset of real arc faults and noise patterns from real-world use worldwide, totaling 60+ GW
- Edge AI - processing within the inverter without needing to send data to the cloud (fast and secure response)
- Self-learning - adjusting patterns for new panel and inverter models via OTA firmware updates
- Cross-validation - verifying signals from multiple sensors before making a decision → reducing false alarms
🎯 GoodWe Models With AFCI 3.0 as Standard:
- Hybrid 1P (ES Uniq): GW5000-12K-ES-C10 - View product
- Hybrid 3P (ET LV): GW10K-20K-ET-L-G10 - View product
- On-Grid 3P (SDT G3): GW10K-50K-SDT - View product
- Commercial (GT): GW125K-GT - View product
6. UL 1699B / NEC Standards
- UL 1699B: The US AFCI standard for PV (solar) systems - requires arc faults to be detected within 30 ms - GoodWe AFCI 3.0 meets this standard
- NEC 690.11: National Electric Code section 690.11 states that "PV systems installed on residential rooftops" must have an AFCI
- IEC 63027: The international standard for AFCI in PV systems
- In Thailand: Currently there is no law mandating it, but many large projects and insurers are starting to require an AFCI
7. Which Inverters Have AFCI 3.0
| Brand/Model | AFCI Version | Standard / Option |
|---|---|---|
| GoodWe (all Hybrid + 3P models) | 3.0 | Built-in as standard |
| Solis S6-EH series | 2.0 | Option |
| Huawei SUN2000 | 2.0+ | Standard on some models |
| SMA Sunny Boy | 2.0 | Option |
| Fronius Primo | 2.0 | Option |
8. Does My Home Need an AFCI?
Highly recommended if:
- ✅ Your home is 2 stories or more + has rooftop solar
- ✅ Animals (birds/rodents) can get into the roof
- ✅ You are in a humid area (near the sea)
- ✅ The home is largely unoccupied during the day (no one to check on it)
- ✅ You want full home insurance coverage
What if my old system doesn't have an AFCI?
You can add an External AFCI Device or Rapid Shutdown, such as the AndSolar AMCL-E2, which disconnects the DC when there is a problem (working similarly to an AFCI but at the panel level).
9. Frequently Asked Questions
Summary
The AFCI is the most important safety system in a solar installation, preventing 80% of fires caused by arc faults in DC wiring. In 2026:
- Choose an inverter with built-in AFCI 3.0 = GoodWe is the best choice
- Add Rapid Shutdown at the module level = AndSolar AMCL-E2
- Inspect the system every 6 months - MC4 connectors, DC wiring, insulation
Consult QES Energy for free. Line: @qesenergy | Tel 083-987-2899