Industrial rooftop solar design begins long before PV modules touch the site. For EPC contractors and electrical engineers, the site survey is the single most important determinant of technical accuracy, BOQ precision, and downstream project safety. In West Bengal—where aging industrial structures, mixed roofing profiles, and variable grid reliability are common—the survey stage must be methodical, instrument-driven, and thoroughly documented.
This guide provides a structured, engineer-friendly survey workflow aligned with current Indian practices, including CEIG norms and state DISCOM requirements. All steps reflect Vedic Solar’s on-ground process for commercial and industrial (C&I) rooftop projects.
1. Pre-Survey Preparation
1.1 Collect baseline data
Obtain from the client:
- Connected load (kVA) and sanctioned load documents
- Monthly consumption (kWh) for 12 months
- DG set ratings & interlock arrangement
- Existing SLD, if available
- Roof access constraints, operating hours, and safety restrictions
This saves 30–40% time during the site visit and ensures you reach prepared with the right instruments.
1.2 Tools checklist
Essential survey tools include:
- Digital laser distance meter
- Clamp meter (AC/DC)
- IR thermometer
- Roof measuring tape
- Compass or smartphone azimuth app
- Drone (optional but increasingly standard)
- Lux meter for indoor inverter room evaluation
- Moisture meter (for RCC roofs)
For sites in coastal West Bengal, where corrosion risk is high, adding a coating-thickness gauge and surface-condition checks prevents fragile structures from being overstressed.
2. Structural Assessment of Rooftop
2.1 Roof type identification
Industrial rooftops typically fall into:
- Metal sheet roofs (trapezoidal, standing seam, KLIP-LOK)
- RCC flat roofs
- Asbestos or old fibre roofs (usually rejected for PV installations)
The surveyor must document:
- Sheet gauge
- Purlin spacing
- Corrosion zones
- Load-bearing history (AHUs, ducts, tanks)
- Thermal movement patterns on long spans
For RCC roofs, record:
- Slab thickness
- Column–beam grid
- Parapet wall condition
- Cracks or deflection signs
Vedic Solar’s rule of thumb for West Bengal’s industrial zones: if the purlin spacing exceeds 1.4 m or the sheet gauge is weaker than 0.5 mm, structural reinforcement or ballasted solutions may be needed.
3. Roof Dimensions and Usable Area Mapping
Accurate dimensioning impacts module layout efficiency, cable routing, and BOS cost.
3.1 Measure:
- Roof length, width
- North–south slope direction
- Height above ground level
- Obstructions (vents, skylights, chimneys, cranes)
- Safe walkways
3.2 Usable area
After deducting clearances:
- 0.6–1.0 m maintenance aisles
- Safety line corridors
- Shadow-affected strips
- Weak zones
Most C&I roofs yield 65–75% usable area; well-planned factories can exceed 80%.
A roof sketch (manual or digital) must be included in the survey report with obstruction coordinates.
4. Electrical Assessment
4.1 LT Panel & Feeder Mapping
Record:
- Main Incoming Panel configuration
- Available breaker ratings
- Spare ACB/MCCB slots
- Maximum demand reading trends
- Earthing grid layout
- DG synchronization and relay settings
Grid reliability in West Bengal varies by industrial cluster, so system design must anticipate voltage fluctuations and flicker during daytime peaks.
4.2 Inverter Room Feasibility
Check:
- Room ventilation (target: 6–8 air changes/hour)
- Dust load
- Clearance for service access
- Cable routing feasibility
- Distance to LT panel (voltage-drop sensitivity)
Where inverter rooms are insufficient, outdoor inverter stations with IP65/67 housings may be preferable.
5. Solar Resource and Shadow Analysis
Even though advanced tools (Helioscope, PVsyst, Soliscope) will be used later, ground-truthing shadows is essential.
Record:
- Nearest tall buildings
- Chimneys (common in chemical and textile units)
- Cranes and gantries
- Parapet wall heights
Take timestamped photos at 9 AM, 12 PM, and 3 PM.
Where drone usage is allowed, capture top-down obstruction photos for precise modeling.
6. Safety and Access Considerations
Document:
- Access stairways
- Anchor points for lifeline systems
- Fragile roof zones
- Lightning protection existence and condition
EPC teams often overlook LP systems; however, DISCOM approvals sometimes require confirmation that the solar array does not interfere with existing lightning conductors.
7. Documentation Required Post-Survey
A complete industrial survey report must include:
- Roof drawings with dimensions
- Shadow analysis images
- Structural notes
- Electrical SLD (as-built)
- Load analysis summary
- Array zoning plan
- Recommendations for inverter placement
- Risks and constraints
This report becomes the foundation for design, BOQ accuracy, and client approvals.
Conclusion
A disciplined site survey prevents design mismatches, reduces rework, and ensures compliance across DISCOM and CEIG checkpoints. Vedic Solar’s structured survey process helps EPC contractors and electrical engineers produce reliable layouts, predictable yields, and clean execution workflows in West Bengal’s operating environment.
BLOG 2 — EPC
Overview of EPC Workflow for Commercial Rooftop Solar (India / West Bengal Edition)
The EPC (Engineering, Procurement, and Construction) workflow defines the technical and operational backbone of every industrial rooftop solar project. For EPC contractors and electrical engineers working in West Bengal, understanding this workflow ensures smooth inter-disciplinary coordination, avoids regulatory delays, and enhances project profitability.
Below is a clear, engineering-oriented walkthrough of the full EPC pipeline as implemented by Vedic Solar for C&I clients.
1. Engineering Phase
1.1 Site survey & feasibility
The engineering workflow begins only after a structured survey (covered in Blog 1). Core deliverables include:
- Feasibility report
- Preliminary array design
- Tentative capacity estimate
- Interconnection feasibility
- Initial risk register
1.2 Detailed design & modeling
Using PVsyst/Helioscope/SolarPro, generate:
- Final capacity utilization based on shading
- String sizing and inverter mapping
- DC/AC ratio selection
- Cable sizing & voltage-drop analysis
- Protection scheme
- SLD (CEIG-ready)
- Earthing & lightning layout
- Structural analysis
1.3 DISCOM application & CEIG compliance
In West Bengal, rooftop systems >500 kW generally require CEIG approval.
Prepare:
- Technical datasheets
- Drawings compliant with CEA Regulations
- Protection coordination sheet
- Compliance certificates
Vedic Solar typically plans a 2–4 week approval cycle depending on DISCOM workload.
2. Procurement Phase
Procurement determines system reliability and long-term O&M outcomes.
2.1 Vendor qualification
Shortlist suppliers based on:
- BIS certification (mandatory for modules & inverters)
- NABL-accredited test reports
- Past performance in humid/coastal climates
- Delivery timelines
2.2 Material selection
Key components:
- Mono PERC / N-type modules
- String/central inverters
- Hot-dip galvanized structures
- DC/AC cables (IS 1584/694 compliance)
- Earthing kits & surge protection devices
- ACDB/DCDB
In West Bengal, high humidity and salt exposure demand strict attention to coating thickness on structures (minimum 80 microns HDG recommended).
2.3 Logistics & staging
Plan material flow to avoid roof congestion:
- Batch delivery schedules
- Secure storage for modules
- Dedicated zones for structure assembly
EPC teams benefit from creating a 3-stage procurement tracker: PO → Dispatch → GRN.
3. Construction Phase
3.1 Site readiness
Before installation:
- Install lifeline systems
- Mark restricted zones
- Conduct toolbox safety meetings
- Set up material lifts (where roofs are >12 m high)
3.2 Mounting structure installation
Check:
- Roof alignment
- Purlin strength
- Fastener torque
- Rail straightness
For RCC roofs, ballast calculations must ensure wind loads per IS 875.
3.3 Module installation
Ensure:
- Module orientation consistency
- Torque per manufacturer specs
- UV-protected cable management
- No module mid-span flex
3.4 DC & AC wiring
Implement:
- Adequate bending radius
- Segregation of AC/DC trenches
- Surge protection installation
- Earthing pits verification (≤1 ohm target, site-dependent)
3.5 Inverter installation
Requirements:
- Ventilation or external IP65 placement
- Proper cable lugging
- MCCB/ACB interconnection
- CT/PT orientation checks
4. Testing, Commissioning & Handover
4.1 Pre-commissioning tests
- Module IV curve sampling
- String polarity checks
- Insulation resistance
- Continuity & earthing verification
- Inverter parameter configuration
4.2 Synchronization & grid compliance
Coordinate with:
- DISCOM officials
- Factory electrical team
- CEIG inspector
Record:
- No-load and full-load inverter behavior
- Protection relay trip tests
- Initial PR% and yield assessment
4.3 Documentation & training
Handover packet includes:
- As-built SLD
- Test reports
- Warranty papers
- Module serial numbers
- Maintenance manual
- SCADA login credentials
Vedic Solar typically conducts a hands-on training session for factory electricians to ensure operational readiness.
5. Post-Commissioning
5.1 Monitoring & O&M planning
Define:
- Daily generation checks
- Fault escalation matrix
- Preventive maintenance schedule
- Inverter firmware update cycles
5.2 Performance evaluation
Collect 1–3 months of generation data to validate:
- Expected energy yield
- Loss breakdown
- PR% stability
This is essential before locking AMC scopes.
Conclusion
A well-executed EPC workflow integrates precise engineering, disciplined procurement, and structured construction management. For industrial projects in West Bengal, Vedic Solar’s process ensures predictable performance, rapid approvals, and long-term asset reliability—critical for EPC contractors and electrical engineers delivering high-quality rooftop systems.
