In the fast-growing solar industry, there’s no shortage of companies offering panels, pricing, and promises. But delivering real-world results—especially for commercial-scale solar systems—demands more than equipment. It requires deep technical understanding, code adherence, and a team that knows how to design systems that pass every inspection from the Authority Having Jurisdiction (AHJ) and meet National Electrical Code (NEC) standards without fail.
At One Place Solar, we pride ourselves not just on building systems, but on engineering confidence—from the earliest layout to final utility approval. Our commitment to NEC and AHJ compliance is not just a checklist item—it’s the foundation of how we design and deliver every project.
To demonstrate how this works in practice, we’re sharing insights from our 246.4 kW ground-mounted solar installation for Special K Hog Farm in McLean, Illinois—a perfect example of how code-aligned design ensures efficiency, scalability, and zero compromise on quality or safety.
Why NEC & AHJ Compliance Matters in Solar Design
When your project is in the hands of inspectors—be it from a local township, a utility company, or a state-level engineer—the outcome depends on one thing: compliance.
- NEC (National Electrical Code) defines safe design practices for wiring, grounding, overcurrent protection, rapid shutdown, interconnection, and more.
- AHJs (Authorities Having Jurisdiction) can include building departments, fire marshals, utility engineers, and electrical code enforcement teams who must approve your permit set.
Failing compliance at any stage can lead to:
- Permit rejections
- Delays in PTO (Permission to Operate)
- Expensive rework
- Legal liabilities
Our clients trust us because One Place Solar designs projects that get approved the first time.
Case Study: Special K Hog Farm, McLean, IL
Project Overview:
- System Size: 246.4 kW DC
- Location: McLean, Illinois (Funks Grove Township)
- Modules Used: 448 x VSUN550-144BMH (550W)
- Inverters: 11 x Fronius Primo 15.0-1 (15 kW)
- Mounting: Ground-mounted, 30° tilt, 180° azimuth
- Interconnection: Line-side tap into 400A load center via exterior ATS
- Racking: Unirac GFT on C-pile driven foundations
NEC Compliance in Practice: Every Detail Engineered
Let’s explore how our design met or exceeded NEC requirements across the board:
1. String Sizing and Voltage Limits (NEC 690.7 & 690.8)
Each of the 28 strings consisted of 16 modules. With each module’s Vmp around 42V, the system voltage stayed well within the 600VDC limit for residential/commercial inverter systems. The inverters selected (Fronius Primo 15.0-1) were paired carefully to avoid voltage clipping and ensure maximum production without violating overvoltage protections.
2. Overcurrent Protection (NEC 690.9 & 705.30)
We used 20A fuses in RS Box-Duo rapid shutdown boxes, sized according to NEC tables for conductor ampacity. All overcurrent protection devices (OCPDs) were documented in our permit set and coordinated with manufacturer specifications and wire derating due to ambient conditions.
3. Grounding and Bonding (NEC 690.43, 690.47, 250)
Proper system grounding was ensured through:
- 8 ft ground rods at inverter pad and combiner locations
- Grounding of racking and module frames with WEEBs and bonding jumpers
- Equipment grounding conductors (EGCs) routed in all AC and DC runs per NEC 250.122
4. Rapid Shutdown (NEC 690.12)
RS Box-Duo devices provided module-level rapid shutdown, fully compliant with UL 1741 and NEC 690.12(B)(2). Our drawings highlighted shutdown boundaries, cable entry locations, and signage required for firefighter access.
5. Conduit and Cable Sizing (NEC 310, 690.31)
All DC and AC conductors were THWN-2, aluminum and copper as appropriate, derated for temperature and conduit fill. Voltage drop was calculated and kept within 2% for DC and 3% for AC, in line with best practices.
6. Labeling and Signage (NEC 690.13–690.55)
We specified:
- Placards for disconnects
- Inverter labeling
- Rapid shutdown stickers
- String combiner labels
This is one of the most common causes of inspection failures—and one we never overlook.
AHJ Compliance: Working with Local and Utility Reviewers
In McLean, the permitting process was governed by Funks Grove Township and the local utility provider. Our success was built on:
Pre-Checked Design Alignment
We confirmed key values—array tilt, azimuth, wind load (90 mph), and snow load (30 psf)—against IBC 2018 and ASCE 7-10 standards to ensure structural design would be accepted with minimal review delays.
Utility Coordination for Line-Side Tap
Instead of backfeeding through a panel (which would have exceeded the 120% rule), we designed a line-side tap with conduit routing, wire sizing, and CT cabinet placement in accordance with utility interconnection standards. This was a critical decision that simplified approval and allowed for a clean inspection.
Engineering Stamps and State Requirements
The electrical and structural designs were PE-stamped for the state of Illinois—meeting all local licensure requirements. Our in-house network of licensed PEs allows us to support this in 40+ states.
One Place Solar’s Compliance-Centric Design Process
Here’s what makes our workflow stand out:
Sales Proposal Phase
We start with a compliant preliminary layout, including shading analysis, inverter grouping, and preliminary performance estimates.
Permit Design Phase
Our in-house engineering team produces detailed site plans, single-line diagrams, racking calculations, and conductor schedules that reflect actual site conditions.
PE Review and Stamping
We submit drawings for structural and electrical stamps based on local wind/snow load and AHJ requirements.
PTO Support
We help submit interconnection paperwork, respond to utility feedback, and resolve any redline comments to push the project to completion.
Beyond Solar: Compliance Across All Services
Our approach to compliance carries through in all our offerings:
- EV charging station design (UL/NEC compliant layout, load calcs, grounding plans)
- Telecommunication tower design (TIA-222 compliance, elevation profiles, structural stamps)
- Battery and hybrid system designs (NEC 706, UL 9540 compliance)
Whether it’s an off-grid battery install, grid-tied PV system, or integrated EV infrastructure, we apply the same precision, professionalism, and compliance rigor.
Final Thoughts: Compliance Isn’t a Feature—It’s a Standard
There are many solar design firms out there. What makes One Place Solar different is our uncompromising focus on compliance— from code to construction.
Whether you’re installing a 10 kW system or a 250 kW array like our McLean project, we help you design it once—and design it right.
We don’t just get plans stamped—we get them approved.
If you’re looking for a partner that ensures every solar installation passes even the toughest inspections, start with One Place Solar.
Contact us to request a sample permit design or to get a quote tailored to your next project.