How we delivered fire-retardant thermoformed enclosures for a utility-scale solar installation in Rajasthan — UL 94 V-0 rated, IP65 weather-sealed, and delivered 5 days ahead of the commissioning deadline with zero field rejections.
520
Enclosures Delivered
50 MW
Solar Farm Capacity
V-0
UL 94 Fire Rating
Zero
Field Rejections
Project Overview
A leading solar EPC contractor approached Formpack with an urgent requirement for fire-retardant inverter enclosures for a 50 MW ground-mount solar farm under construction in Rajasthan's Thar Desert.
Client
A leading solar EPC contractor
Requirement
Fire-retardant PC-FR inverter covers and combiner box enclosures for a 50 MW ground-mount solar farm in Rajasthan
Part Dimensions
String inverter covers: 850 × 520 × 180 mm; Central inverter housings: 1,400 × 900 × 250 mm
Material
PC-FR (Polycarbonate Fire Retardant) — UL 94 V-0 rated, co-extruded with UV-stable ASA cap layer
Core Challenge
Deliver 500+ fire-rated enclosures in 8 weeks to meet commissioning deadline — with IP65 weather sealing and 25-year design life in desert conditions
Final Outcome
All 520 enclosures delivered 5 days ahead of schedule, passing on-site fire safety and IP65 ingress testing with zero rejections
The Challenge
Building enclosures for a solar farm in the Thar Desert demanded materials and processes that could survive extreme heat, monsoon rain, DC arc fault risks, and an immovable commissioning deadline.
The solar farm's DC architecture required all inverter enclosures to meet UL 94 V-0 flammability standards. DC arc faults generate sustained heat — the enclosure material must self-extinguish, not merely resist ignition. The EPC contractor's insurance underwriter mandated third-party fire test certificates for every material batch.
Rajasthan's Thar Desert reaches 50°C ambient in summer. Solar inverters generate significant internal heat — surface temperatures on enclosures can exceed 80°C during peak operation. The material needed to maintain structural integrity from -10°C winter nights to 130°C continuous use without warping or embrittlement.
Despite the arid climate, monsoon season brings torrential rain, dust storms, and humidity spikes. Every enclosure required IP65-rated sealing — precision-formed gasket channels, integrated drip edges, and sealed cable gland cutouts to protect sensitive power electronics from moisture ingress.
The EPC contractor had a fixed commissioning date tied to a power purchase agreement. Any delay in enclosure delivery would cascade into grid synchronisation penalties. The 520-unit order had to be tooled, prototyped, validated, produced, and shipped to site within 8 weeks from purchase order.
Our Solution
We leveraged our vertically integrated supply chain — from in-house FR sheet extrusion to CNC-trimmed, IP65-sealed enclosures — to compress the timeline and maintain complete material traceability.
We selected PC-FR (Polycarbonate Fire Retardant) as the primary material — UL 94 V-0 rated, self-extinguishing, with continuous use temperature of 130°C. To address UV degradation in desert conditions, we co-extruded sheets with a UV-stable ASA cap layer on the weather-exposed face, providing 10+ years of colour stability without painting. Third-party fire test certificates were obtained for every extrusion batch.
Our engineering team conducted a Design for Manufacturability review with the EPC contractor's electrical engineers. We optimised the enclosure geometry for single-shot thermoforming — integrating ventilation louvers, cable entry points, mounting bosses, and gasket channels directly into the mold. CNC-machined aluminium tooling was designed for both string inverter covers and central inverter housings, with cooling channels for consistent cycle times.
First-article prototypes were produced within 10 days of tooling completion. Each prototype underwent dimensional inspection, fire testing (V-0 confirmation), and IP65 ingress testing — including water jet and dust chamber tests. The EPC contractor's quality team approved prototypes on-site, clearing the path for production.
With approved tooling and validated prototypes, we ramped to full production — running 2 thermoforming machines simultaneously. String inverter covers were formed at 3.5-minute cycle times; central inverter housings at 5.5 minutes. CNC trimming, gasket channel finishing, and cable gland cutout drilling were completed in-line. Daily output averaged 18-20 enclosures per day across both variants.
Every enclosure was individually inspected against a 12-point checklist: dimensional accuracy, wall thickness uniformity, gasket channel depth, cable gland alignment, surface finish, fire rating label, and IP65 seal integrity. Each unit was laser-marked with a unique serial number, material batch code, and production date — providing full traceability from raw pellet to installed enclosure.
Enclosures were nested, foam-padded, and palletised for truck transport to the Rajasthan site. Custom packaging was designed to prevent scratching of the ASA cap layer during transit. All 520 units were delivered in 3 shipments over 5 days — arriving 5 days ahead of the commissioning deadline.
Material Comparison
The EPC contractor's original specification called for painted galvanised steel enclosures. Here's why thermoformed PC-FR proved superior for this solar application.
| Property | PC-FR Thermoformed | Galvanised Steel | Verdict |
|---|---|---|---|
| Fire Rating (UL 94) | V-0 (self-extinguishing) | Inherent (non-combustible) | Both pass |
| Tooling Cost | ₹2-4 lakh (CNC aluminium) | ₹8-15 lakh (press tooling) | PC-FR wins |
| Part Weight | 30-50% lighter | Baseline (heavy) | PC-FR wins |
| Corrosion Resistance | Immune (no coating needed) | Requires galvanising + painting | PC-FR wins |
| Electrical Insulation | Inherently insulating | Conductive (grounding required) | PC-FR wins |
| IP65 Sealing | Formed gasket channels | Welded + gasket applied | Comparable |
| UV Stability | ASA cap layer (10+ years) | Paint dependent (repainting) | PC-FR wins |
| Lead Time (500 units) | 6-8 weeks | 10-14 weeks | PC-FR wins |
Results
520
Enclosures Delivered
String inverter covers and central inverter housings — all PC-FR V-0 rated
70%
Tooling Cost Savings
CNC-machined aluminium molds vs steel injection molds — at 500-unit volumes
Zero
Field Rejections
100% first-pass acceptance at site — no rework, no replacements, no delays
5 Days
Ahead of Schedule
Delivered before commissioning deadline despite aggressive 8-week timeline
PC-FR thermoformed enclosures meet the same UL 94 V-0 fire safety standards as sheet metal — while being 30-50% lighter, corrosion-proof, and electrically insulating
Co-extruded ASA cap layers provide decade-long UV stability in desert conditions without painting — reducing lifecycle maintenance costs for solar EPC contractors
CNC-machined aluminium tooling costs 70% less than steel injection molds at 500-unit volumes — making thermoforming the optimal process for solar farm enclosure quantities
Integrated gasket channels, cable gland cutouts, and ventilation louvers formed in a single shot eliminate multi-piece assemblies and seam-joint leak points
In-house sheet extrusion with batch-level fire test certification provides complete material traceability — critical for solar farm insurance and compliance documentation
Vertically integrated supply (pellet → sheet → formed part) compresses lead times and eliminates supply chain dependencies on imported materials
Send us your inverter specifications, site conditions, and volume requirements. We'll recommend the right fire-retardant material, provide a DFM review, and quote your enclosures — typically within 48 hours.