Solar Detailed Design: Complete Engineering Drawing Checklist for EPC Projects
Solar detailed design is the stage where a project concept becomes a controlled set of drawings, schedules and calculations that a contractor can build from. For an EPC team, the work is complete when every drawing is traceable to a design basis, consistent with the others, correctly numbered and issued with the right revision. The table and checklists below help check that.
Concept, basic, detailed and IFC: how they differ
Stage | Purpose | Typical content |
|---|---|---|
Concept design | Test feasibility and rough size | Capacity estimate, rough layout, single-line sketch, outline cost |
Basic engineering | Fix the technical basis and main equipment | Design basis, preliminary layout, SLD, equipment list, preliminary yield model |
Detailed engineering | Develop calculations and drawings for each discipline | Calculations, layouts, schedules, specifications, drawings for review |
IFC (Issued for Construction) | Release approved, controlled documents for building | Final drawings, schedules and specifications with revision control and transmittal |
Projects use these terms differently, so agree the definitions in the contract or execution plan.
Drawing and document checklist
The table maps each drawing type to its purpose, key inputs and common review checks.
Drawing | Purpose | Key inputs | Common review checks |
|---|---|---|---|
General arrangement / site plan | Show plant boundary, major areas and access | Survey, boundary, setbacks | Boundary and coordinates match survey; setbacks shown |
PV layout | Show table and row positions, blocks and equipment | Module and structure data, survey, yield model | Matches yield model; row pitch, setbacks and slopes checked |
Stringing layout | Show string groupings and numbering | Module and inverter datasheets, layout | Voltage and current limits met; string IDs unique |
Inverter and transformer layout | Show equipment positions and clearances | Vendor drawings, layout | Clearances and access verified against vendor data |
DC cable routing | Show DC routes and trenches | Layout, stringing, cable schedule | Lengths consistent with schedule; separation respected |
AC and MV cable routing | Show AC and MV routes to substation | SLD, layout, cable schedule | Crossings detailed; bend radius and separation respected |
Single-line diagram | Show electrical connectivity and ratings | Equipment data, protection study | Matches schedules and layout |
Equipment layout (substation, control room) | Show internal arrangement | Vendor data, SLD | Clearances, escape routes, cable entries |
Cable schedule | List every cable with size, length and route | SLD, routing, calculations | Sizes match calculations; tags unique |
Trench and cable details | Show trench sections and crossings | Cable schedule, soil data | Depth, bedding, separation and markers |
Earthing layout | Show earth grid, risers and equipment connections | Soil resistivity, fault level | Conductor size, grid coverage and connections to structures |
Lightning protection layout | Show air terminals and down conductors | Risk assessment | Coverage of buildings, masts and equipment |
Mounting structure drawings | Show tables, members and connections | Structural report | Sizes match model; coating, tolerances and notes |
Pile and foundation drawings | Show pile type, embedment and positions | Geotech report, reactions | Positions match layout; embedment matches design |
Equipment foundation drawings | Show pads and bases | Vendor loads, geotech | Loads and anchor details match vendor data |
Roads and drainage | Show alignments, levels, culverts and outfalls | Survey, hydrology | Levels continuous; culverts at crossings; widths checked |
Fencing and gates | Show perimeter and access control | Site plan, specification | Gate positions match roads; clearances |
SCADA and communication | Show network architecture and cabling | Utility and client requirements | Protocols and redundancy as specified |
Metering diagram | Show revenue and check meters | Utility requirements | CT and PT ratios, accuracy class |
Signage and safety drawings | Show warning and information signs | Safety plan, standards | Locations and wording match site conditions |
As-built drawings | Record what was built | Site markups | Revised drawings match installation |
Cross-discipline coordination
Drawings are only useful if they agree. Coordination points to review:
• PV layout, stringing and the yield model use the same module count and geometry.
• SLD, equipment schedule and cable schedule agree on ratings, tags and quantities.
• Pile positions in structural drawings match the PV layout coordinates.
• Civil levels match equipment foundation drawings and trench levels.
• Drainage does not conflict with cable trenches or pile positions.
• Earthing connects to structures and equipment as shown on structural and electrical drawings.
• Vendor drawings are checked against clearances and loads before release.
A formal coordination meeting with overlay drawings, using a shared coordinate system, finds most clashes before they reach site.
Drawing numbering and revision control
Use a simple, documented system. A typical drawing number includes project code, discipline, drawing type and sequence, such as PRJ-ELE-SLD-001. Keep a drawing register listing number, title, discipline, revision, date, status and author. Each revision must have a revision note describing the change and a transmittal to recipients. Superseded drawings should be marked and removed from site circulation. Define status codes (for example, for review, for approval, IFC, as-built) in the execution plan so everyone interprets them in the same way.
Title block and drawing quality checks
Before issue, confirm that each drawing has:
• Project name, client, drawing title, number and revision.
• Scale, north arrow and coordinate system.
• Legend, abbreviations and general notes.
• Reference drawings and design documents.
• Author, checker and approver identification as per project procedure.
Common mistakes
• Issuing drawings before the layout is frozen.
• Using different module dimensions in layout and structural drawings.
• Updating the SLD without updating the cable schedule.
• Letting drawing revisions drift between disciplines.
• Forgetting site-specific details such as trench crossings and culverts.
• Releasing drawings without a documented review.
When to involve a specialist
Specialist engineers help when a project has a tight schedule, multiple stakeholders or a lender requiring detailed review. Solyug Energy provides solar design consultancy for EPC teams, supports utility-scale solar projects, and shares guides in the resource center.
Standards and references
• IEC 62446-1: documentation and commissioning of grid-connected PV systems.
• IEC 62548: PV array design requirements.
• Project specification, execution plan and client drawing standards.
Frequently Asked Questions
What is the difference between basic and detailed engineering in solar?
Basic engineering fixes the design basis and main equipment. Detailed engineering develops calculations, layouts, schedules and drawings for each discipline.
What does IFC mean on a drawing?
Issued for Construction. It indicates the drawing has been approved and may be used on site, under revision control.
Which drawings are most often inconsistent?
The SLD versus cable schedule, layout versus structural drawings, and civil levels versus equipment foundations.
How many drawings does a solar project need?
It depends on capacity, complexity and contract requirements, so there is no reliable general figure. Use a drawing register built from the checklist above.
Who checks the drawings?
A checker within the design team, then a discipline lead, and an approver from the EPC or owner’s engineer according to the project procedure.
Do as-built drawings matter?
Yes. They record the final installation for operation, maintenance, warranty and future modification, and are often a contractual requirement.