How a Solar Installer Reduced Costs with a 1000V DC Combiner Box 2 In 1 Out MCB Type

Customer Background

GreenVolt Energy, a regional solar EPC company based in California, specializes in commercial rooftop PV systems between 50 kW and 200 kW. With a team of 12 field installers, they complete 15 projects per year. Historically, they used separate DC circuit breaker housings for each string, leading to bulky arrays on rooftops.

What Made Their Current Setup Unsustainable?

GreenVolt's typical 100 kW system required 20 strings at 1000V DC, each with a standalone DC MCB mounted on a rail inside a large enclosure. This consumed 40% more rooftop space than necessary. Wiring between breakers and the inverter was messy, with long cable runs and multiple splice points. Their service manager reported that nuisance tripping occurred twice a week on average, caused by coordination issues between separate breakers.

The consequences were direct: each trip required a site visit costing $150 in labor, and installation of a single system took 12 days instead of the planned 8. Material waste due to excess wire and brackets added $2,000 per project.

Why Did They Choose the Soutya 1000V DC Combiner Box 2 In 1 Out MCB Type?

After evaluating three suppliers, GreenVolt’s engineering lead, Marco, selected the Soutya 1000V DC Combiner Box 2 In 1 Out MCB type for three reasons:

• Space savings: The unit combines two string inputs and one output with an MCB in a single compact enclosure, reducing mounting footprint by 60% compared to individual breakers.
• Simplified wiring: Pre-wired terminals and a clear labeling system cut field wiring time. The unit is IP65 rated for outdoor use.
• Compliance: The combiner box meets IEC 62548:2016 requirements for PV array design, giving GreenVolt confidence in code compliance.

Marco also appreciated that Soutya provided a custom labeling option for string numbers, which reduced commissioning errors.

How Was the Combiner Box Deployed in the Field?

GreenVolt used the Soutya combiner boxes in three consecutive projects over six months. Each project had a similar layout:

1. Planning phase: The design team created a new string-to-combiner wiring diagram, allocating two strings per box. They specified 12 combiner boxes per 100 kW system.
2. Pre-assembly: Combiner boxes were pre-mounted on custom-built racks in the shop, including cable gland installation and labeling. This shifted 4 hours of work per box away from the rooftop.
3. Field installation: Installers mounted the racks, connected the PV strings using MC4 connectors, and routed the single output cable to the inverter disconnect. The MCB settings were verified on each box.
4. Commissioning: A multimeter check confirmed correct polarity and voltage. No coordination issues were found.

One challenge was that string polarity could be reversed if installers rushed. Soutya’s combiner box includes a reverse polarity indicator LED, which immediately alerted the crew. This feature prevented what would have been a $500 diode repair.

What Were the Measurable Results?

Beyond numbers, GreenVolt noticed fewer callbacks from customers system downtime. Their customer satisfaction score rose from 3.8 to 4.6 out of 5.

What Did the Customer Say?

Marco, GreenVolt’s engineering lead, commented: “We were skeptical another combiner box, but the Soutya unit made our installers’ lives easier. The reverse polarity indicator alone saved us from mistakes. We’re now specifying it for all new projects.”

What Can Other Solar Installers Learn?

• Consolidate protection: Replacing multiple breakers with a combiner box reduces points of failure and speeds up wiring.
• Pre-assemble off-site: Mounting boxes and labeling in the shop cuts rooftop labor by up to 30%.
• Choose integrated diagnostics: Features like reverse polarity indication prevent expensive field errors.

References

1. IEC 62548:2016 — Photovoltaic (PV) arrays — Design requirements
2. Chen G, Mou X. Study on the coordination between MCB and RCBO in low-voltage power distribution systems. Electrical Engineering, 2022, 104(3): 1823-1835.