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newSchoolWorks.com › VoTechWorks › Building & Construction › Solar / PV Installation › PV Mounting Systems: Rooftop and Ground-Mount Installation › Lesson 6
BLD-SOLA09-04 · Lesson 6 · 10 clock hours · field

Ground-Mount Systems and Final Inspection Readiness

Objective. Students will assemble a section of driven-pier or surface-ballasted ground-mount racking in the field exercise yard, then complete a pre-inspection punch-list checklist and correct all identified deficiencies before a simulated AHJ walk-through.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed professional engineer or master tradesperson or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.

Ground-Mount Systems: Overview

Ground-mount PV systems sit on structures built directly on the earth rather than on a roof. Two foundation types dominate the industry: driven-pier (also called ground-screw or driven-post) systems, where steel posts are driven or screwed into native soil, and surface-ballasted systems, where weighted bases—typically concrete blocks—hold the racking frame in place without penetrating the ground. Each type has distinct installation steps, site considerations, and inspection requirements.

Ground-mount arrays are common in open fields, commercial lots, and rural properties. Because they are independent structures, they are subject to structural loading requirements (dead load, wind uplift, snow load) calculated by a licensed engineer. You will always work from an engineered drawing set that specifies pier spacing, embedment depth, hardware sizes, torque values, and module layout. Following that drawing is not optional—departing from it voids the engineering and can trigger a failed inspection or, worse, a structural failure.

Foundation Installation

Driven-Pier Systems

Piers are typically galvanized steel pipe or C-channel driven by a hydraulic post driver or hand-driven with a slide hammer for smaller jobs. Before driving, confirm there are no buried utilities—always call 811 (Dig Safe/USA) before any ground disturbance, even when driving rather than digging. Pier spacing must match the engineered drawing exactly. After driving, check plumb with a level on two perpendicular faces and verify top-of-pier elevation against your grade reference string line. Piers that are out of plumb or at the wrong elevation create cumulative alignment problems through the entire rack.

Ballasted Systems

Ballast blocks are placed on a prepared, graded surface. The engineering drawing will specify block weight, spacing, and the maximum allowable slope. On soft or uneven ground, a compacted gravel pad is typically required. Place blocks carefully—they are heavy and tip hazards exist. Never substitute lighter blocks or reduce block count without a revised engineering stamp.

Racking Assembly

Once foundations are set, horizontal rails (struts) are attached to the piers or frame uprights using the specified hardware. Follow the draw sequence: install bottom chords first, then tilted rafter members, then module rails. Use the correct bolt grade—substituting a lower-grade fastener changes the load path and is a code violation.

Leveling and alignment matter throughout. Use a string line or laser level to confirm rails are co-planar before torquing. A rack that looks close enough by eye is often out of spec when measured. Modules that sit on a twisted frame crack over time.

Torque every fastener to the value shown on the engineered drawing or manufacturer's installation manual (IOM). Record each torque application in a torque log: location, fastener size, specified torque, actual torque, date, and installer initials. This log is part of the documentation package the AHJ may request.

Module Installation and Bonding

Mount dummy modules (or real modules on live jobs) starting from the end indicated on the layout drawing. Use the manufacturer-specified clamp—end clamps at the array perimeter, mid-clamps between modules. Clamps must engage the frame flange squarely; an off-center clamp can crack the module frame or allow a module to slip in wind. Torque mid-clamps and end clamps to the values in the IOM.

Bonding (equipment grounding) must be continuous across all metal racking components and module frames. Many modern racking systems use bonding washers integrated into the clamp, but always verify with a continuity check using a low-resistance ohmmeter or a dedicated ground continuity tester. A missing or failed bond is a critical safety deficiency—it means exposed metal could become energized without a safe fault-current path.

Install all required labels before the inspection: array circuit labels, DC Warning labels, and any system labels required by the adopted electrical code. Missing labels are a common inspection failure item.

PPE and Site Safety

Pre-Inspection Punch-List

Before any AHJ walk-through, experienced installers perform their own systematic inspection. A 20-item punch-list covers: pier plumb and embedment, rail alignment and levelness, hardware torque verification, clamp engagement and torque, bonding continuity, module clearances from adjacent structures, conduit support spacing, label placement, documentation completeness (layout drawing, torque log, permit card posted), and site cleanliness. Catch your own deficiencies—an AHJ who finds problems you missed loses confidence in your whole installation.

Simulated AHJ Walk-Through

In industry, the Authority Having Jurisdiction (AHJ) is the local building or electrical inspector who has legal authority to approve or reject your installation. At the walk-through you are expected to: present your documentation package without being asked, explain attachment methods and load paths in plain language, cite the applicable code or standard when asked (e.g., the NEC article covering equipment grounding, or the IBC chapter covering structural loads), and stand beside—not in front of—the structure so the inspector can see it. Answer questions directly; if you don't know, say so and offer to look it up rather than guessing.

A thorough documentation package and a clean, code-compliant installation are the two things that turn an inspection into a quick approval.

Key terms10

Driven-pier foundationA ground-mount foundation type in which steel posts are driven or screwed directly into native soil to support the racking frame, without concrete footings.
Ballasted rackingA ground-mount system held in place by the weight of concrete or other heavy blocks resting on the ground surface, requiring no soil penetration.
Torque logA written record documenting the location, fastener size, specified torque value, measured torque value, date, and installer initials for each fastened connection in a PV racking system.
Equipment bonding (equipment grounding)The electrical connection of all exposed metal racking and module frame components to the grounding system, providing a low-impedance path for fault current to protect people from shock.
Engineered drawing setSite-specific structural and electrical drawings stamped by a licensed engineer that specify pier spacing, embedment depth, hardware specifications, torque values, and load calculations for a ground-mount array.
Authority Having Jurisdiction (AHJ)The organization, office, or individual legally responsible for enforcing the requirements of a code or standard and approving equipment, installations, and procedures.
Punch-list inspectionA systematic pre-inspection review in which the installing crew checks their own work against a defined checklist of requirements, identifying and correcting deficiencies before the official AHJ walk-through.
Continuity testA low-voltage electrical test performed with an ohmmeter or dedicated tester to verify that a bonding or grounding conductor provides an unbroken, low-resistance conductive path across all connected metal parts.
Mid-clamp / End-clampModule mounting clamps used to secure PV module frames to the rail; mid-clamps sit between two adjacent modules and grip both, while end-clamps secure the outermost module at the array perimeter.
Load pathThe route by which structural forces (dead load, wind, snow) travel from the PV modules through the racking components, into the foundation, and into the earth.

Worked examples4

1. Your engineered drawing specifies pier spacing of 8 ft on center. The array section is 40 ft long and begins with a pier at the 0 ft mark. How many piers are required for this section, and at what positions (in feet from the start) should each pier be located?
  1. Identify the starting position: first pier at 0 ft.
  2. Divide the total length by the spacing to find the number of spans: 40 ft ÷ 8 ft = 5 spans.
  3. Number of piers = number of spans + 1 = 5 + 1 = 6 piers.
  4. List pier positions by adding 8 ft increments: 0, 8, 16, 24, 32, 40 ft.
Answer: 6 piers, located at 0, 8, 16, 24, 32, and 40 ft from the start of the section.
2. A mid-clamp manufacturer specifies a torque of 15 ft-lb. After installing a section you find your torque wrench reads in in-lb. What value in in-lb should you set on the wrench?
  1. Recall the conversion: 1 ft-lb = 12 in-lb.
  2. Multiply the specified torque by the conversion factor: 15 ft-lb × 12 in-lb per ft-lb = 180 in-lb.
Answer: Set the torque wrench to 180 in-lb.
3. You are checking pier plumb on a 48-inch-tall driven pier. Your level shows the top of the pier is displaced 1.5 inches horizontally from the base over the full 48-inch height. Expressed as a ratio (rise : run), is this within a commonly accepted plumb tolerance of 1:100?
  1. Set up the ratio of horizontal displacement to vertical height: 1.5 in displacement over 48 in height.
  2. Simplify by dividing both values by 1.5: 1.5 ÷ 1.5 = 1 and 48 ÷ 1.5 = 32, giving a ratio of 1:32.
  3. Compare 1:32 to the tolerance of 1:100. A ratio of 1:32 means the pier is out of plumb more than the 1:100 limit (1:32 is a larger deviation than 1:100).
  4. Conclusion: the pier fails the plumb tolerance and must be corrected before attaching rails.
Answer: The ratio is 1:32, which exceeds the 1:100 plumb tolerance. The pier must be re-driven or adjusted.
4. Your 20-item punch-list identifies 5 deficiencies. After corrections, the peer team re-inspects and finds 2 items were not fully resolved. What percentage of the original deficiencies remain open, and does this clear the threshold for the simulated AHJ walk-through (all 20 items must be resolved)?
  1. Calculate the percentage of original deficiencies still open: 2 remaining ÷ 5 original = 0.40 = 40%.
  2. Check the pass criterion: all 20 punch-list items must be resolved before the simulated walk-through.
  3. With 2 items still open, the requirement is not met.
Answer: 40% of the original deficiencies remain open. The team does not meet the threshold and must resolve the remaining 2 items before the simulated AHJ walk-through.

The math in this lesson3

Learners count piers at 8 feet on center along a 40-foot array.
6.RP.37.RP.3N-Q.1
Brush up in the math halls at newSchoolWorks.com:
In class: Field assembly on the training yard: student teams assemble a ground-mount rack section following a provided engineered drawing, including installing piers or ballast blocks, attaching horizontal struts, leveling the structure, and mounting dummy modules using the correct clamp sequence. · Peer punch-list inspection: teams swap completed rack sections and systematically walk through a 20-item pre-inspection checklist covering alignment, hardware torque, grounding continuity, module clearances, and label placements; each discrepancy is written up with a corrective action. · Simulated AHJ walk-through led by the instructor acting as inspector; students stand at their corrected assembly, answer questions about attachment methods, load paths, and code compliance references, and present their completed documentation package (layout drawing, torque log, inspection checklist).
Materials: Ground-mount racking kit (driven-pier or ballasted type), dummy PV modules, torque wrench, level, tape measure, engineered drawing set, 20-item pre-inspection checklist, label stock, bonding hardware, PPE (hard hat, safety glasses, gloves, steel-toed boots)
Check: All 20 punch-list items resolved before simulated walk-through; instructor (as AHJ) scores the documentation package and verbal responses on a 10-point rubric — pass requires 8/10. Any critical safety deficiency (unsecured module, missing bond) is an automatic fail requiring reassembly and re-inspection.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Safety and PPE / Site Preparation
1. Before driving ground-mount piers at a new site, what must the installation crew do first?
Installation and Commissioning / Documentation
2. A torque log is best described as a document that records:
Safety and PPE / Structural Integrity
3. During peer punch-list inspection, a team finds that one mid-clamp on the racking section is finger-tight only and has not been torqued. This should be classified as:
Electrical Systems / Grounding and Bonding
4. Which tool is used to verify that bonding is continuous across all racking metal components?
System Design and Layout
5. On a 64-ft long array section with driven piers spaced every 8 ft on center, starting at 0 ft, how many piers are needed?
Codes, Standards, and Regulations
6. The Authority Having Jurisdiction (AHJ) is best defined as:
System Design and Layout / Racking
7. A ballasted ground-mount system differs from a driven-pier system primarily because it:
Safety and PPE / Electrical Safety
8. An installer is connecting new grounding conductors to an existing energized DC string on a ground-mount system under bright sunlight. What is the correct action before touching any conductors?
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