How a Solar EPC Cut DC Arc Fault Costs by 35% with Soutya AFCI Combiner Box

Customer Background

Midsize solar EPC company based in Stuttgart, Germany, designs and installs commercial rooftop PV systems across Europe. With a portfolio of 80 MW under long-term O&M contracts, the company serves manufacturing facilities, logistics centers, and cold storage operators. Each project ranges from 500 kW to 2 MW, and the company is responsible for both construction and ongoing maintenance.

The company's O&M team had been dealing with an increasing number of inverter trips and thermal events caused by DC arc faults. Aging connectors, wire chafing, and loose terminations in the string circuits were the main culprits. As the portfolio expanded, the cost of reactive maintenance began to erode profit margins.

The Challenge: Undetected DC Arc Faults

DC arc faults are dangerous because they sustain without drawing enough current to trigger a standard fuse or circuit breaker. In the company's existing combiner boxes, only string fuses and surge protectors were installed. These provided overcurrent and surge protection, but they could not detect series arc faults that occur in damaged cables or loose connections.

The consequences were tangible. In the 12 months before the project, the team responded to 14 inverter trips that were traced back to damaged connectors. Each trip required a site visit, thermal imaging scans, and manual inspection of every connection in the string. A single troubleshooting session averaged eight hours. In addition, two near-miss incidents were reported where an arc had melted the insulation of a connector, causing smoke and risking a fire. The estimated cost per such event, if not caught, could exceed $50,000 in asset damage and downtime.

Why the Soutya DC AFCI Combiner Box?

The company evaluated three options. The first was adding AFCI modules at the inverter input, but that only monitors the combined output of all strings and cannot identify which string has a fault. The second option was replacing all cable connectors with higher-grade ones, which would not address future degradation. The third option was the Soutya DC AFCI combiner box with a 12-in-1 configuration.

The decision came down to three key advantages. First, the Soutya combiner box provides per-string arc fault detection. Each of the 12 inputs is monitored independently, so a fault is immediately localized. Second, the unit integrates both AFCI and overcurrent protection in one enclosure, simplifying installation and reducing the number of components to inspect. Third, it complies with UL 1699B and supports the design requirements of IEC 62548, giving the EPC confidence for both European and export markets.

Implementation and Application Process

The project was deployed across three commercial rooftop arrays, each with 8 to 10 strings. The total project took six weeks from planning to commissioning. The existing combiner boxes were removed and replaced with the Soutya DC AFCI combiner box. Because the 12-in-1 layout matched the existing string routing, the team reused most of the DC cables, saving material costs and installation time.

A typical difficulty was retrofitting into confined spaces. The new combiner box has a larger footprint than a simple fuse-only unit, so mounting brackets needed to be adjusted on one roof. The team solved this by using a stainless steel backplate and flexible conduit, completing the retrofit without changing the structural layout.

After installation, the team connected the Modbus RTU output to the existing SCADA system. The combiner box streamed per-string current, voltage, and arc fault status to the remote monitoring center. Commissioning tests included a simulated arc fault, which the unit cleared in under 0.5 seconds while identifying the exact string.

Quantifiable Results

• Reduced troubleshooting time by 90%: Average fault response time dropped from 8 hours to 45 minutes because the AFCI box immediately identifies the faulty string.
• Lowered O&M costs by 35%: The three sites now require fewer emergency callouts. Annual savings amount to $18,000 across the portfolio.
• Decreased inverter downtime by 60%: By preventing sustained arcing that would cause inverter trips, the sites experienced 60% fewer unplanned disconnections.
• Detected two arc faults early: During the first 12 months, the unit caught two series arc faults in their initial stage, preventing potential fires and damage.

The overall impact went beyond numbers. The O&M team shifted from reactive repair to proactive inspection. The data collected from the combiner box enabled them to schedule cable replacements during planned maintenance windows than on an emergency basis.

Client Testimonial

“The Soutya DC AFCI combiner box gave our crew the ability to identify a failing connector before it became a fire. The per-string alarm and data logging have changed how we manage our PV portfolio.”

Lessons and Recommendations

1. Place arc fault detection at the string level. Inverter-level detection cannot localize faults and leaves long DC cable runs unprotected.
2. Combine monitoring with protection. A combiner box that reports per-string current and status creates actionable data for predictive maintenance.
3. Budget for training. Arc fault symptoms differ from overcurrent events, and technicians need to understand the technology to respond .

If the company were to run this project again, they would install Soutya AFCI boxes on all new projects from the start, than retrofitting. Standardizing on the 12-in-1 configuration would simplify their spare parts inventory and make remote diagnostics more consistent across sites.

References

1. UL 1699B:2018 Photovoltaic (PV) DC Arc-Fault Circuit Protection. Link
2. IEC 62548:2016 Photovoltaic (PV) arrays — Design requirements. Link
3. IEC 60364-7-712:2017 Low-voltage electrical installations — Part 7-712: Solar PV power supply systems. Link