A California-based solar EPC company specializing in commercial rooftop projects needed a faster, safer way to connect PV strings to their DC collection network. After piloting the 600V/1000V Door Clutch DC Box 2 in 1 Out YB2-2/1 from singielectric, they reduced installation time per combiner box from 45 minutes to 22 minutes and cut the number of enclosure units on site by 20%. This is how they did it.
The company, a mid-sized EPC with 60 employees, manages roughly 40 MW of solar installations per year across California and Nevada. Their projects range from 1 MW rooftop arrays to 15 MW ground-mount systems. They handle everything from design engineering to commissioning, with their own in-house installation crews.
Before this project, they were under pressure to compress construction timelines. The rising cost of labor and interconnect delays meant that every week saved on site fed into project profitability. They needed a DC combining solution that could be installed faster without compromising safety or long-term reliability.
Their existing DC combiner boxes were a constant bottleneck. Each box accepted one string input, so a 5 MW project with 500 strings required 500 separate enclosures. That meant more mounting points, more cabling, and more potential failure points. Wiring the input terminals inside the boxes was slow work—technicians had to remove four screws to open the door, reach inside a cramped enclosure, and torque each connection carefully. Average installation time was 45 minutes per box, and the crew worked in hot attics or on sun-exposed rooftops.
The old boxes also caused maintenance headaches. Monthly inspections required loosening the same screws, which stripped after repeated cycles. In one year, they replaced 12 door latches due to corrosion and wear. On the safety side, working with 1000 VDC circuits while fiddling with screws increased the risk of accidental arc flashes. The company knew they needed a different approach.
The engineering team assessed three alternatives: continuing with the old boxes, ordering custom-built enclosures from a local fabricator, or switching to the singielectric YB2-2/1. Custom boxes came with a six-week lead time and a price tag 30% higher. The cheaper imported boxes failed their field test—two units had loose terminals after only three months of thermal cycling.
The YB2-2/1 stood out for its door clutch mechanism. The door opens and closes without any screws, using a spring-loaded clutch latch that engages securely with a single quarter-turn. Technicians no longer need tools to access the interior. The unit also combines two string inputs into one output, which matches their typical string layout perfectly. Rated for both 600 V and 1000 V systems, the box gives them flexibility across different module brands and string volt-levels.
Another decisive factor was the build quality of the terminal block. The YB2-2/1 uses a reinforced polyamide housing with nickel-plated copper busbars, capable of handling the heat generated in continuous high-amperage operation. The IP65 rating ensured dust and water protection for outdoor installations.
The project began in early 2024 on a 5 MW commercial rooftop in Fresno, California. The EPC company started with a pilot phase of 50 units installed on the north-east array. After validating performance for two weeks, they ordered the remaining 450 units for the rest of the site.
The implementation followed a deliberate process:
One expected challenge was ensuring that the door clutch would stay sealed after repeated open-close cycles on a vibrating rooftop. The crew deliberately opened and closed one box 50 times during the pilot. The clutch still held the door firmly sealed with no deformation. That test convinced the team to standardize on the product.
The switch to the YB2-2/1 produced measurable improvements across the project:
Overall, the installation phase finished 12 days ahead of schedule, allowing the company to move crews to another project and avoid $20,000 in potential liquidated damages.
The project manager for the Fresno site, who oversaw the switch, said: “The door clutch alone saves us several minutes per box during every visit. It’s the first time we’ve had a DC box that makes troubleshooting faster, not a punishment. We’ve standardized on the YB2-2/1 for all new commercial proposals.”
For other EPC firms considering similar upgrades, three takeaways stand out:
The team noted that if they were to redo the project, they would have run the pilot on a larger section of the roof from the start. The 50-unit pilot was enough to prove reliability, but a 100-unit pilot would have allowed them to train more installers earlier and shorten the rollout phase by another week.
