Quality and counterfeit risks: what to check on delivery

Most material reaches site in good condition from honest suppliers. But the Indian market also has under-sized cable, fake branded breakers, cross-mated connectors, re-labelled modules and structures with paint where galvanising should be. Once installed, these are expensive to find. A 30-minute check at delivery protects the customer, the subsidy and your name.

Modules

Paperwork first

Before unloading, compare the delivery against:

• Invoice and delivery challan: model, wattage, quantity, serial numbers
• Flash test report: measured Pmax for every serial number, at or above nameplate
• DCR certificate (for subsidised jobs): every serial listed
• ALMM listing for that model and BIS registration (R-number)

Physical inspection

• Packaging: pallets upright, straps intact, no crushed corners. Photograph any damage before signing the challan, and write "received damaged, subject to inspection" on it.
• Glass: no cracks, chips or "spider web" fractures.
• Frame: no dents or bends, corners tight.
• Backsheet: no scratches, bubbles or wrinkles.
• Junction box: lid sealed, cables and connectors intact, connector make as per datasheet.
• Cells: look along the glass for snail trails (dark lines in the cells), discolouration or visible cracks.

Quick field check: Voc

On a sunny morning, measure a sample module's Voc with a multimeter (DC volts, correct range, probes on the MC4 pins with the module disconnected).

Worked example: at 11 am in Hyderabad the cell temperature is about 50 °C. Expected Voc for the 550 Wp module above:

49.9 × [1 − 0.0027 × (50 − 25)] = 49.9 × 0.9325 = 46.5 V

• 45–47 V: normal.
• About 31 V: one bypass diode shorted (one-third of the cells bypassed). Reject.
• Very low or zero: open circuit inside the junction box.

Short-circuit current (with a DC clamp meter and a proper shorting method) should be roughly proportional to irradiance. Do not short modules with bare wires; use a suitable rated switch or the inverter's string measurement.

Inverters

• Model, rating and serial on the box and rating plate match the invoice.
• BIS registration for the model, and the warranty card or online registration.
• Factory seal on the box intact; no signs of use (scratched mounting holes, dust inside the connectors, old firmware dates).
• Accessories present: mounting bracket, DC connectors of the same make as the inverter's inputs, AC connector, Wi-Fi dongle, manual.

Cables

Under-sized and fake cable is common. Check:

• Printing along the sheath: manufacturer, size (4 mm² or 6 mm²), standard (EN 50618 or IEC 62930), voltage (1.5 kV DC), and sequential length markings.
• Copper, not copper-clad aluminium (CCA): scrape a strand; CCA shows silver-grey metal under a thin copper skin.
• Conductor weight: copper weighs 8.96 g/cm³. A 4 mm² conductor therefore weighs 4 × 8.96 = 35.8 g per metre. Strip 1 m of insulation and weigh the conductor on a kitchen scale. Less than about 34 g means the copper is under-sized.
• Resistance: a class 5 tinned 4 mm² conductor should not exceed about 5.09 Ω per km at 20 °C (IEC 60228). A 100 m coil should read no more than about 0.51 Ω end to end, measured with a low-resistance ohmmeter.

MC4 connectors

• Same maker and type as specified; certificate to IEC 62852.
• Fakes often have thin, poorly plated contacts, loose fit, and no maker marking inside.
• Check that the crimp contacts match the cable size (4 mm² vs 6 mm²).

Breakers, RCCBs and SPDs

Counterfeit branded MCBs and RCCBs are sold in many markets.

• Buy only from authorised distributors and keep the invoice.
• Compare weight and print quality with a known genuine piece; fakes are often lighter, with blurred printing and poor terminal screws.
• Use the maker's verification method if available (many have a QR code or hologram check).
• Test every RCCB with its test button after installation; it must trip.
• SPDs should show the voltage rating (Ucpv for DC), class or type, and the standard (IEC 61643-31 for DC, IEC 61643-11 for AC).

Structures and fasteners

• Hot-dip galvanised steel should have a dull grey, even zinc coat. Measure thickness with a magnetic coating gauge at several points; compare with the order specification (often 80 microns for HDG; check the job specification). Painted or pre-galvanised steel sold as "HDG" is a common substitution.
• Fasteners: stainless steel grades (SS304/SS316) marked on the head where specified; a magnet sticks strongly to ordinary steel, weakly or not at all to most austenitic stainless.
• Earthing material: check copper-bonded rods for bonding thickness and earthing strips for size.

Recording and rejecting

1. Photograph every label, serial number and defect.
2. Note shortages and damage on the delivery challan before signing.
3. Inform the supplier in writing (email or WhatsApp) the same day, with photos.
4. Quarantine rejected items clearly marked "Do not install".
5. Update the serial list for the portal and the warranty file.

Key points

• Match model, serials, flash test, DCR certificate, ALMM and BIS registration before installing modules.
• A quick Voc check with temperature correction finds shorted bypass diodes and open circuits.
• Weigh a stripped metre of cable: 4 mm² copper is about 36 g/m; less means under-sized or CCA.
• Buy breakers and connectors from authorised sources, and never cross-mate MC4 brands.
• Photograph, note on the challan, and report damage the same day; never install a dropped module untested.

Check yourself

1. A 550 Wp module reads 31 V open-circuit on a sunny noon. What is the likely fault?
2. What should one metre of genuine 6 mm² copper conductor weigh?
3. Why must you write remarks on the delivery challan before signing it?