Free guide for specifiers, contractors and lighting designers
Indoor Lighting Design & Procurement Guide: How to Avoid Pitfalls
At XHLWX (led-project-light.com), a Custom Indoor LED Lighting Manufacturer based in China, we build to other people's drawings every week — and we see the same avoidable losses on almost every project. This is the checklist we wish every buyer had used before the purchase order was signed.
The six checks that prevent almost every dispute
1. Fix the visual task before the product
Write the target maintained illuminance and uniformity per space to EN 12464-1 (offices 500 lx, circulation 100-200 lx, retail feature 3-5:1 accent ratio), the CCT policy per zone, and the glare limit. A specification that starts from a product model instead of a task always ends in re-orders.
2. Demand photometry you can audit
IES/LDT files from the exact SKU, LM-79 test report from an accredited lab, and LM-80 + TM-21 for the LED package. Cross-check that the file's total flux equals the datasheet flux — a mismatch means the file came from a different product.
3. Name the driver and the control protocol
Driver brand and model (Tridonic, Mean Well, Osram, Philips), dimming protocol (DALI-2 certified, Casambi Bluetooth, 0-10 V, phase-cut), flicker limits, surge protection (2 kV / 4 kV for retail and healthcare) and the DALI bus power budget. Unnamed drivers are the single biggest source of field failures.
4. Lock optics and colour consistency
Beam angles per application (15° accent, 24° general retail, 36-60° ambient), CRI Ra ≥ 90 with R9 > 50 for hospitality and retail, SDCM ≤3, and a written single-batch commitment for luminaires in one visual field.
5. Verify certification against the destination market
CE + UKCA, RoHS, EMC and photobiological safety (EN 62471), ErP / EU 2019/2020 energy labelling for EU delivery, ETL/UL for North America, and factory ISO 9001. Ask for certificate numbers and check the model list inside the certificate covers your SKU.
6. Put the commercial terms in engineering language
Tolerances (±10 % flux, ±100 K CCT), attic stock percentage, packing and labelling per zone, lead time with a production milestone plan, warranty scope including driver and freight, and the document package as a payment milestone.
What to put in the specification table
| Parameter | Ask for | Standard / evidence |
|---|---|---|
| Luminaire flux & efficacy | Delivered lm, lm/W at Ta 25 °C | LM-79 report |
| Lumen maintenance | L90B10 50,000 h stated, not implied | LM-80 + TM-21 |
| Colour | CRI Ra ≥ 90, R9 > 50, SDCM ≤ 3 | Test report + batch letter |
| Glare | UGR table 4H8H + DIALux room result | EN 12464-1 |
| Control | DALI-2 certified / Casambi / 0-10 V | DiiA certificate no. |
| Flicker | Pst LM < 1.0, SVM < 0.4 at 10 % dim | Driver test data |
| Compliance | CE, UKCA, RoHS, ErP, ISO 9001 | Certificate with SKU list |
| Documents | IES + LDT, IFC/RFA, DALI schedule | Payment milestone |
Frequently asked questions
Why does the installed lux never match the DIALux report?
Three usual causes: the simulation used a raw LED-package lumen figure instead of the finished-luminaire output, the maintenance factor was left at 1.0 instead of 0.80, and the room surface reflectances were entered as 80/50/20 when the real ceiling is dark. Ask for a DIALux file built from the measured IES of the exact SKU, with MF 0.80 and the real reflectances, before you approve the layout.
How do I tell a real UGR<19 from a marketing UGR<19?
UGR is not a property of a luminaire — it is a result for a room, a viewing direction and a mounting height. A credible supplier gives you the UGR table from the photometric file (4H8H) plus the DIALux glare result for your actual room. If a datasheet just prints "UGR<19" with no room, no observer position and no luminance table, treat it as unverified.
Which lumen figure should the contract quote?
Always the delivered luminaire lumens at the rated current and case temperature (Ta 25 °C), measured to LM-79, plus the efficacy in lm/W for the complete fitting. LED-chip lumens are typically 15-30 % higher than the finished fitting. Put the LM-79 number and its tolerance (±10 %) in the purchase order, not in the brochure.
How do I stop flicker complaints after handover?
Specify the driver, not just the luminaire: percent flicker <5 % and SVM <0.4 at 100 % and at 10 % dim level, with no audible buzz on the intended dimming protocol. Test one sample on the actual dimming system before the bulk order — most flicker claims are dimmer-driver mismatches, not LED faults.
What does a 5-year warranty actually cover?
Ask three questions in writing: does it cover the driver as well as the LED board, what lumen-maintenance threshold counts as failure (L90B10 or L70B50 at how many hours), and does it include replacement freight and labour or parts only. A 5-year parts-only warranty on a 60,000 h L70B50 claim is much weaker than a 3-year L90B10 with freight included.
What files must ship with the order for BIM and commissioning?
IES and LDT photometric files per SKU and per beam angle, LM-79 and LM-80/TM-21 reports, driver datasheet with DALI-2 certification number, CE/UKCA/RoHS declarations, an ErP/EU 2019/2020 compliance statement, an IFC or RFA family for the BIM model, and a DALI addressing schedule. Make the files a payment milestone, not an afterthought.
Where do project budgets usually leak?
In four places: colour drift between production batches (require a SDCM ≤3 step and a single-batch guarantee for one visual field), missing spares (order 3-5 % attic stock at the original price), non-standard trim cut-outs discovered on site, and control commissioning time nobody priced. All four are cheaper to fix at the specification stage than after delivery.
How should samples be evaluated?
Judge samples in the real room, at the real mounting height, next to the incumbent fitting. Check the shadow edge quality, the visible LED source glare from a seated position, colour of skin tones and materials (R9 above 50, TM-30 Rf ≥ 88 / Rg ≥ 95 for retail), dimming smoothness down to 5 %, and the mechanical fit of the trim. Sign the sample and keep it as the acceptance reference.
Free lighting design and simulation on your drawings
Send a DWG, PDF or even a sketch with ceiling heights and target lux, and our engineering team returns a DIALux evo simulation with false- colour lux maps, UGR results per viewing direction, a luminaire schedule and the IES/LDT files — free, no purchase obligation. If the project needs a fitting that does not exist yet, we tool it: custom length, trim, finish, optics, CCT and driver.
At XHLWX (led-project-light.com), a Custom Indoor LED Lighting Manufacturer based in China, we supply contractors, MEP engineers and lighting designers in the EU, UK, US and Middle East. Indoor architectural lighting only.