Solar Facility: 31 Issues Found

The project

A solar photovoltaic facility in Adams County, Colorado. InspectMind performed a plan review of the electrical and structural drawings, identifying electrical sizing errors, grounding specification conflicts, and structural coordination issues before construction.

Project type

Renewable energy · Solar · Colorado

Codes referenced: International Building Code · NFPA 70 (NEC) · ADA Standards

Critical findings (6)

1. Incorrect Applicable Building Code Edition

   Structural

   Critical

   The drawing cites the '2021 International Building Code (IBC)' as the applicable code, but the project is being reviewed against the 2024 IBC. Construction documents must show conformity to the currently adopted code provisions.

2. Structural Certification Based on Obsolete Standards (2016 structural loads / ADM 2015)

   Structural

   Critical

   The structural engineering letter on the drawing certifies the system for compliance with the '2024 International Building Code' but explicitly states that Wind Loads are based on the 2016 edition of the IBC-referenced structural loads standard and Aluminum design is based on 'Aluminum Design Manual 2015'. The 2024 IBC adopts the current edition of the structural loads standard and ADM 2020. The current edition introduced significant changes to wind load determination (including new tornado load requirements referenced in IBC 1602.1) compared to the 2016 edition. Using 2016 wind speeds/methodology and ADM 2015 for an IBC 2024 project is a direct violation of IBC Sections 1609.1.1 and 2002.1.

3. Undersized Equipment Grounding Conductor in Inverter Output Schedule

   Electrical

   Critical

   The Inverter Output Schedule (Rows 3 and 4) specifies a #6 Aluminum Equipment Grounding Conductor (EGC) for the combined circuits (AC CMB 1 to AC DISC 1 / AC BRKR 1). These circuits have a calculated 'Circuit Current x125%' of 173.5A. Per NFPA 70 (NEC) 690.8 and 240.6, this requires an Overcurrent Protection Device (OCPD) rating of at least 175A (the next standard size). According to NFPA 70 Table 250.122, the minimum size Aluminum EGC for a 175A or 200A OCPD is #4 AWG. The specified #6 AWG Aluminum conductor is undersized, posing a safety hazard during fault conditions.

4. Incompatible Racking Specification for Open Frame Carport

   Structural

   Critical

   The Site Plan clearly identifies the PV mounting location as an "OPEN FRAME CARPORT STRUCTURE". The designation "Open Frame" typically indicates a structure where modules are mounted directly to framing members or rails without a solid underlying roof deck. However, the provided Project Specifications (Sheet E-802) exclusively specify "SnapNrack Seam Clamp" and "S-5-S Clamp" products. These are specifically designed for attachment to standing seam metal roof decks. These attachment components are physically incompatible with an open frame structure. Furthermore, the structural engineering letter provided refers to "rooftop installation" and "Flush-Mounted PV modules," which contradicts the carport application shown.

5. Conflicting Inverter Voltage and Current Ratings

   Electrical

   Critical

   Sheet E-701 Detail 1 explicitly specifies the Inverter 1 & 2 AC disconnect ratings as 480V and 72.2A. However, the label schedule on Sheet E-702 for 'ALL INVERTERS' lists conflicting ratings of 208V and 139A. This indicates a major coordination issue regarding the system voltage (480V vs 208V).

Sample high priority findings (13 total)

1. String quantity callout (5) conflicts with specifications table (10) on same drawing sheet

   Electrical

   High

   The site plan shows a callout '5 STRINGS OF 16 MODULES EA.' for the solar array, but the project specifications table on the same drawing shows 'STRING QUANTITY 10' with 'STRING SIZE 16 MODULES'. With 160 total modules at 16 modules per string, the correct string quantity should be 10 (160÷16=10), not 5 as shown in the plan callout.

2. Incorrect UL Standard Specified for Inverters

   Electrical

   High

   Equipment Note 7 requires inverters to be listed to "UL 1704". However, UL 1704 is not the applicable standard for inverters; UL 1741 is the standard for Inverters, Converters, and Controllers. IBC 104.2.1 requires that listings be germane to the provision requiring the listing, and referencing an incorrect or non-existent standard for the equipment violates this requirement.

3. Missing Photovoltaic System Dead Load

   Structural

   High

   The drawing provides wind and snow loads but fails to indicate the dead load of the rooftop-mounted photovoltaic panel system. The building code explicitly requires the dead load of the PV system, including the rack support system, to be shown on the construction documents.

4. Potential Safety Switch Rating Conflict with Inverter Listing

   Electrical

   High

   The Inverter datasheet specifies a "Max. OCPD Rating" of 125A. The Safety Switch datasheet specifies a switch rating of "200A" without explicitly listing the required fuse size. While the 200A switch frame is required to hold a 125A Class H/R fuse (which physically requires the 101-200A frame), specifying a 200A switch without a specific note to install 125A fuses creates a significant risk that 200A fuses will be installed, which would violate the inverter's UL listing limit of 125A (IBC 2701.1, NFPA 70 110.3(B)).

5. Incorrect Conduit-to-Cord Connection Assembly

   Electrical

   High

   Detail 2 depicts a "CORD GRIP" installed on the conduit side of a threaded coupler. Cord grips (strain relief fittings) are listed for sealing around flexible cords, not for connecting to rigid conduit or gripping wires inside a conduit. This application violates the listing instructions (IFC 603.1 / NFPA 70 110.3(B)). Furthermore, a single cord grip is shown with multiple "PV CONDUCTORS", which typically requires a specific multi-hole bushing to maintain rating.

6. PV Module Model Number Inconsistency Between Equipment List and Inverter Schedule

   Electrical

   High

   E-601 Equipment List specifies PV module model as 'TALESUN TD6172M 450' while E-611 Inverter Schedule specifies 'TD6I72M 450'. The character difference ('1' vs 'I') in the model number indicates different module designations.

7. DC String Quantity Mismatch - Project Specifies 10 Strings but Schedule Documents Only 8

   Electrical

   High

   E-601 Project Specifications indicates 'STRING QUANTITY 10', but E-611 DC String Schedule only documents 8 strings (1-1 through 1-4 and 2-1 through 2-4). Two strings are missing from the cable schedule documentation.

8. Inverter Model Designation Inconsistency Between Equipment List and Inverter Schedule

   Electrical

   High

   E-601 Equipment List specifies inverter as 'CPS AMERICA SCA-25KTL-US 208' while E-611 Inverter Schedule shows 'SCA25KTL-DO/US-208'. The 'DO' designation present in E-611 is absent from E-601, and there are hyphen differences suggesting potentially different inverter variants.

9. Disconnect Switch Voltage Rating Mismatch: E-601 Requires 600V but Specified DH324FRK Rated 240V

   Electrical

   High

   The single line diagram on E-601 specifies the PV Fused AC Disconnect (item E) with a 600V 3-phase 3-wire rating. The equipment list on E-601 specifies Eaton model DH324FRK for this disconnect application. However, the product datasheet on E-801 indicates the Eaton DH324FRK has a voltage rating of 240V, which does not meet the 600V rating requirement shown on the single line diagram.

10. Conflicting and Outdated NEC Code References for Signage

    Electrical

    High

    The drawing contains contradictory code references regarding the applicable National Electrical Code (NEC) edition. The 'NOTES AND SPECIFICATIONS' explicitly require compliance with the '2023 ARTICLE 110.21(B)', indicating the project is designed to the 2023 NEC. However, the specific label details reference 'NEC 2017' sections (e.g., 690.13(B), 690.5(C), 705.12(B)(2)(3)(b)).

Issue categories

Structural

Structural issues found during plan review

Electrical

Electrical issues found during plan review

Code Compliance

Code Compliance issues found during plan review

Fire Protection

Fire Protection issues found during plan review

Value delivered

• 31 issues surfaced before construction
• 6 critical electrical and structural violations identified
• Electrical sizing errors and grounding conflicts caught
• Structural coordination issues flagged