Worked example: car park with 12 columns of 6 metres

The starting points

The site in this example is fictional but realistic: a car park of 100 by 60 metres (6,000 m²) next to a company building, in use until late evening, with lorry traffic at the loading docks. The client asks for an average illuminance of 20 lux, the guide value EN 12464-2 gives for car parks with heavy traffic. A quiet car park needs only 5 to 10 lux.

Fixed choices: twelve conical steel TURRIS columns of 6 metres in RAL 9005, VIA street luminaires on the 60 mm spigot and one NEXUS column cut-out with fuses per column. All prices exclude VAT; Lichtplein supplies businesses only.

Step 1: how many lumens are needed

The rule of thumb for an open area starts with area times required illuminance: 6,000 m² × 20 lux = 120,000 lumens that must actually land on the surface.

Two corrections follow. Part of the light falls outside the area or is lost in the optic; for a street luminaire with a wide road optic at 6 metres we use a utilisation factor of 0.5 in this example. The luminaire also gets dirty and its output drops slightly over the years: maintenance factor 0.8. Installed, you therefore need 120,000 / (0.5 × 0.8) = 300,000 lumens, or 25,000 lumens per column with twelve columns.

Step 2: the luminaires

The VIA range runs from 25 to 100 W at up to 160 lm/W, IP66, with 10 kV surge protection. Three variants side by side, each with the same factor of 0.4 (utilisation times maintenance):

• 1 × 50 W per column (LP-VI112, 20 to 50 W set by dip switch, 6,750 lm): 12 × 6,750 = 81,000 lm installed, about 5 lux average. Suitable for an overflow car park.
• 1 × 100 W per column (about 15,000 lm): 180,000 lm, about 12 lux. Meets the 10 lux for medium traffic.
• 2 × 100 W per column on a double bracket: 360,000 lm, about 24 lux. This is the variant that reaches the required 20 lux with a margin for soiling.

For this example we choose the third variant: 24 luminaires of 100 W, 2,400 W in total. Choose the version with DALI-2 or AstroDIM if the site may dim to 50 per cent after midnight; the extra cost of the driver can then pay for itself through lower consumption.

Step 3: column positions and uniformity

Twelve columns on 6,000 m² means 500 m² per column. A logical layout is three rows of four: the rows at 10, 30 and 50 metres from the long side, the columns at 12.5 / 37.5 / 62.5 / 87.5 metres. The 25 metre spacing is a good four times the mounting height, which we treat as the practical upper limit for a road optic at 6 metres.

That is exactly why a rule of thumb is not enough. The average is right, but the uniformity Uo (minimum divided by average) must be at least 0.25 for a car park, and only a calculation proves that. For 350 euros excluding VAT Lichtplein produces one via /en/lichtplan/: you receive an isolux plot, the tilt angle per luminaire and a bill of materials that can be ordered straight away. Glare towards the entrance and neighbouring properties can also be included in the calculation.

Step 4: columns, cut-outs and fuses

The 6 metre TURRIS column is conical, made of S235JR steel, hot-dip galvanised and, for this project, additionally powder coated in RAL 9005 (jet black). It is supplied to the Dutch standard, with a door opening for the cut-out and a 60 mm spigot on which the VIA luminaire clamps with adjustable tilt.

A NEXUS column cut-out goes behind the door. With two luminaires per column you choose the version for two fuses, so each luminaire is protected separately: two porcelain E27/DII screw caps, two fuse links and an earth braid to the column.

Electrically: 24 × 100 W = 2,400 W, a good 10 A. Spread the three rows over three phases and switch via a photocell or an astronomical time switch in the distribution board.

Complete bill of materials

• 12 × TURRIS conical steel lighting column 6 m, RAL 9005
• 24 × VIA LED street luminaire 100 W, IP66, optic as per the lighting calculation (with DALI-2 or AstroDIM as preferred)
• 12 × double bracket for two luminaires on one column (price on request)
• 12 × NEXUS column cut-out for 2 fuses
• 24 × porcelain E27/DII screw cap
• 24 × DII fuse link
• 12 × earth braid
• 1 × lighting calculation with isolux plot and bill of materials

Not in the bill of materials, but in your budget: foundations, underground cable, groundworks, the distribution board and installation. Lichtplein does not supply these.

Indicative budget

Based on the price bands in our range, excluding VAT and excluding cut-outs. The columns are priced separately on request and are therefore not included in the sum:

• Columns: 12 TURRIS steel columns of 6 metres in RAL 9005, sharp price on request, answer within 48 hours
• Luminaires: the 100 W version sits at the top of the VIA band of 29 to 235 euros; 24 × 235 = 5,640 euros
• Lighting calculation: 350 euros
• NEXUS cut-outs, screw caps, fuse links and brackets: on request
• Total for luminaires and calculation, excluding columns: about 6,000 euros excluding VAT

By comparison: the variant with one 50 W luminaire per column (LP-VI112, 155 euros) comes to 12 × 155 + 350 = about 2,200 euros excluding columns, but delivers only a quarter of the light. Twelve columns stays below the project threshold of 20 columns; add them to your quotation request and you receive a sharp price within 48 hours. Lead time: luminaires within 5 working days from European stock, steel columns 3 to 5 weeks. So order the columns first.

Frequently asked questions