HID shoebox lights with low conversion rates are highly efficient when measured at the source. However, it does not take into account the amount of light that hits the target area (system efficiency). System efficiency is affected by a myriad of factors, including losses due to trapped light, protective covers or lenses, non-standard operating temperatures, and power conversion losses. The system efficiency for HID shoebox lights is generally only 70% of the source efficiency compared to the LED shoebox lights (whose system efficiency is closer to 90%). Hence, it is obvious that the more practical lighting solution is the LED.  

The significant advantage of HID shoebox light is that their initial purchase price will be much lower in some cases, particularly with low and high-pressure sodium bulbs. Typically, LED shoebox lights make up for their higher purchase price with reduced maintenance and energy costs across a specific payback period. Similarly, another explicit tradeoff with the HPS (High-pressure sodium-vapor) lamp, in particular, is its monochromatic yellow with an abysmal Color Rendering Index.

Furthermore, HID shoebox lights carry with them a myriad of inherent potential problems. Amongst them, the major issues include repetitive maintenance and replacement costs in both parts and labor (HID shoebox lights have a much shorter lifespan than LEDs), potentially hazardous waste (internal mercury), and dangerous emissions (UV). Such situations occur if the bulb breaks, the casing experiences some form of failure, or other similar concerns like longer warm-up times, inability to dim effectively, or shorter warranty coverage.

Therefore, though the trend nowadays is to go with LED shoebox lights, one needs to be cautious. Choosing products with a guaranteed lifespan is of utmost importance to avoid tensions, frequent maintenance work, and high costs associated with it.

How to Choose the Parameter of the Commercial LED Shoebox Fixture?

A sound and reliable lighting system that can improve night-time visibility will provide efficient, high-quality light with minimal glare.

The average road surface illuminance is a vital evaluation index for roadway lighting. The luminous flux may be calculated using the formula jotted below, which helps ascertain the total perceived power emitted by a light source.

E = Ø / A

E_av = F * U * K * N / (W_eff * S)

W _eff = W_s – X_L

Where:

“Ø” = luminous flux, “E” = illuminance, “A” = irradiated area （m²）

“E_av” = average road surface illuminance, “F”= rated luminous flux （Lm）

“S” = luminaire mounting spacing （m）

“W_eff” = effective road width,  W_s = actual road width，X_L = overhang

Due to the varying installation heights, elevation angles, layout methods, road widths, etc., of the street lights, we should also consider the rated luminous flux of the street light source, the “utilization factor (U).”

For the purpose of maintaining the average illuminance of the road surface, it is necessary to consider the lumen maintenance, the protection level, the cleaning cycle, and the “maintenance factor (K)” to calculate the rated luminous flux.

Since the street lights are arranged in different ways, such as a single row, double row symmetrical, double row staggered, etc., which affects the average illuminance, the “arrangement factor (N)” needs to be considered as well.

Table 1 Recommended Values for High Pedestrian Activity Areas

To explain the calculation method, we have illustrated an example below.

On the main road, with high pedestrian activity, the road width is 20m, luminaire mounting spacing 25m, installation height 10m, overhang length 1.5m, elevation angle 15°, and the luminaires are arranged on only one side of the road. What power should be selected?

Select the LED shoebox light with an IP65 protection level that suits the project environment.

Refer to table 1, and choose Eav = 20Lx.

W_eff / H is 18.5 / 10 = 1.85, elevation angle 15°, certainty U is 0.69, K is 0.7.

20 = F * 0.69 * 0.7 * 1 / (20 – 1.5) / 25

F = [ (W_s – X_L) * S] * E_av / U * K * N

  = [ (20 – 1.5) * 25] * 20 / (0.69 * 0.7 * 1)

  = 9250 / 0.483

  = 19151 Lm

Generally, the lumen efficiency of LED Shoebox lights is 100-130Lm/W, but the corresponding power should be 150W-200W. Lepro provides LED shoebox luminaires with a lumen efficiency of up to 130Lm/W.  Hence, only 150W power is enough.

Through the design software DIALUX, the LEPRO LED shoebox illuminants helps meet or exceed the maintained average horizontal luminance and average-to-minimum uniformity ratios.

How to Choose the Mounting Accessories of Commercial Shoebox Fixtures?

There are generally three installation methods for shoebox lights：

1. Slip Fitter: Round Pole 

2. Direct Bracket: Square Pole

3. Trunnion Bracket: Wall Mounting

When positioned in parking lots and roads, we generally recommend choosing the first or second category depending on the actual installation situation.

For optical design or any questions, please contact Lepro. We provide various types of parking lot lights 100w to 300w for your choosing.

The post How Do You Choose Shoebox Fixtures for Commercial Areas? appeared first on Lepro Blog.

Lighting Analysis of a Parking Lot

The chart below exhibits that the illuminance requirement of a parking lot is appropriately 50lx, and its uniformity ratio is around 0.6.

      Uo means uniformity ratio of illuminance

Based on the information presented in the table above, if you plan on using the 150w parking lot light, we strongly advocate our customers to utilize 2 LED parking lot lights with 19500lm (150w) each, mounted 20-25 feet high above the ground. Likewise, the distance between the poles should range anywhere between 50 and 80 feet.

It is evident from the chart outlined below that we also offer different wattages ranging from 100w to 300w with various lumen outputs. However, if you want to learn more about the different types of lights we offer along with the ideal lighting solution that suits your parking lot, please get in touch with us via our website.

Lighting Requirements of Parking Lot Lights

Besides the basic illumination requirements of the parking lot lights, we also need to take into consideration the uniformity of illumination (Uo), color rendering (Ra), and the correlated color temperature (CCT) of the light source. Additionally, glare is also an important indicator used to measure the quality of the luminaire. High-quality venue lighting creates a relaxed and visual environment for drivers. The following chart explained hereunder shows the requirements.

How to choose lumen and wattage for a parking lot?

If you are looking at replacing your existing metal halide parking lot light, here is a list of our top recommendations.

If you have a new project with no existing parking lot lights, please do not hesitate to contact Lepro with your layout design. Once we get all the necessary information, a list of our premium quality recommended LED fixtures and lighting solutions that meet your demands will immediately reach you for use in your parking lot! This is a basic service we offer all our customers to help them review how many poles and illuminants will be required along with a detailed cost estimate.

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