Abstract: The codes such as "Fire Prevention Code for Architectural Design," "Technical Standard for Emergency Lighting and Evacuation Guidance System," and "Design and Installation of Emergency Lighting" specify the ground low light level requirements for the placement of lighting fixtures in buildings and structures. In daily design, the average illuminance calculation method or point illuminance calculation method from the "Design and Installation of Emergency Lighting" (19D702-7) collection is typically used to calculate illuminance and arrange lighting fixtures, or directly use the illuminance test charts provided by emergency lighting manufacturers. Whether the actual installation using wall-mounted or suspended ceiling methods can reach the required illuminance levels specified in the "Design and Installation of Emergency Lighting" (19D702-7) collection cannot be directly verified. To address this, the article conducts a simulation analysis using the DIALux evo software to verify the design of emergency lighting. Case studies have confirmed that the simulation design results for emergency lighting using DIALux evo software are reliable and effective.
Keywords: Emergency Lighting; Evacuation Lighting; Average Luminance Calculation Method; Point Luminance Calculation Method; DIALux evo Software
0 Preface
Emergency lighting is the illumination activated due to the failure of normal lighting power supply. National regulations and industry standards have clear requirements for the design of emergency lighting. Among them, the illuminance of emergency lighting fixtures is an important evaluation criterion for lamps. In daily design, the illuminance of emergency lighting fixtures is often calculated using the formula calculation method, the illuminance test tables of emergency lighting fixture manufacturers, and the built-in mini-programs of Tianzheng Electrical. When the coefficient in the formula calculation method is not one-to-one corresponding, interpolation calculation is繁琐; the installation height and method in the illuminance test table of the manufacturer are limited; and the utilization coefficient and light source parameters of the built-in mini-program of Tianzheng Electrical cannot be matched. Additionally, the calculation results of the aforementioned methods cannot be displayed intuitively in the form of an equal illuminance map.
This article utilizes the widely-used DIALux evo software in lighting design to simulate emergency egress lighting. The design results are presented in the form of isophote diagrams for intuitive visualization, verifying the outcomes of formula calculations. This study holds great significance for enriching the methods of emergency lighting design.
Emergency Lighting Overview
Emergency lighting includes evacuation lighting, safety lighting, and standby lighting. Evacuation lighting is used to ensure that evacuation routes are effectively identified and utilized; safety lighting and standby lighting are employed to ensure the safety of individuals in potential danger. The illuminance of evacuation lighting refers to the low-level horizontal illuminance on the ground and should be calculated using the point illuminance method. The illuminance of safety lighting and standby lighting both refer to the average level illuminance on the work surface and should be calculated using the average illuminance method.
Emergency lighting is a crucial component of emergency illumination. Article 10.3.2 of the "Code for Fire Prevention in Building Design" (GB 50016—2014), Article 3.2.5 of the "Technical Standard for Fire Emergency Lighting and Evacuation Guidance System" (GB 51309—2018), and Table 3.2.5 of the National Standard Collection "Design and Installation of Emergency Lighting" (19D702-7) list the ground low-level illumination requirements for emergency lighting in different locations. The collection "Design and Installation of Emergency Lighting" also provides the detection scope for emergency lighting in various typical locations. These regulations and standards define the goals and scope for the design of emergency lighting.
2. Emergency Lighting Design Requirements
Evacuation lighting ground-level illuminance varies depending on the location, ranging from 1lx to 3lx, 5lx, and 10lx. The article takes the design and verification of evacuation lighting in non-people-intensive areas as an example.
When selecting emergency lighting sources, requirements such as color rendering and startup time should be met, and a comprehensive technical and economic analysis should be conducted based on the efficiency or performance, lifespan of the sources, lamps, ballasts, and the like, to determine the lighting scheme. When designing evacuation lighting, in addition to meeting the illumination requirements of special locations, LED lamp sources should be used for economic and energy-saving effects; high color temperature lamps are recommended as they can accelerate personnel's response to surrounding events, enhancing the efficiency of emergency evacuation. When the lighting source is set at 8 meters or less from the ground, A-type emergency lighting fixtures should be chosen for electrical shock protection, with a working voltage not exceeding DC 36V. Ceiling-mounted lamps should not be made of glass and should be chosen from energy-saving and environmentally friendly materials to reduce the threat to personnel from lamp damage. In tunnels and damp locations, the protection rating of the lamps should not be lower than IP65.
- Luminance Calculation Method
Emergency lighting has two methods of luminance calculation: average luminance calculation and point luminance calculation. According to the National Standard Atlas "Design and Installation of Emergency Lighting," the detection range for egress lighting is along the center line of the corridor, with a width of half the corridor's width (see Figure 1).
Figure 1: Illustration of emergency lighting layout and illumination detection range
3.1 Method of Average Luminance Calculation
Average illuminance calculation formula is:
（1）
In the formula: Eav - average illuminance on the working surface (lx)
Luminous Flux (lm)
N - Number of light sources
U - Utilization Coefficient
A - Work Face Area (m²)
K - Maintenance Coefficient for Lighting Fixtures.
The Average Luminance Method can calculate the direct light flux of light sources and the reflected light flux from various surfaces in the room. By using parameters such as the average luminance on the working surface and the lighting utilization coefficient, the number of light sources required within a fixed area, i.e., the number of luminaires meeting the illuminance requirements, can be determined. The specific calculation method is as follows.
(1) Confirm the original data, including the lumens F of the lighting fixtures, the length L and width W of the area, the room height hr, the maintenance coefficient K, and the reflectance ρ.
(2) Calculate the room index, Ri.
（2）
(3) Seek an effective reflectance ratio, temporarily disregarding the reflectance ratio for emergency lighting, i.e., ρ=0.
(4) Refer to the lighting maintenance coefficient table in Figure Set 19D702-7 to determine the lighting maintenance coefficient.
(5) Utilize the lighting utilization coefficient table of Collection 19D702-7 and calculate the utilization coefficient Ui by means of interpolation.
(6) Calculate the number of lighting fixtures, N.
（3）
3.2 Luminous Efficacy Calculation Method
Photometric calculation formula is:
（4）
Horizontal illuminance produced by the point light source (lx)
- Intensity of the point light source in the direction of angle illumination (cd)
h is the installation height (or calculated height) of the light source (m).
θ is the angle between the normal to the ground through the light source and the incident light beam (see Figure 2).
Figure 2: Light Source Illumination Diagram
The point illuminance calculation method can determine the point illuminance values within an evacuation lighting area. It is based solely on the direct light from the lighting fixtures, without considering the effects of inter-reflections from room surfaces. This method is the recommended evacuation lighting illuminance calculation method for the Atlas 19D702-7, as detailed below.
(1) Determine the original data. Including the installation height h of the light source, and the horizontal distance r.
(2) Calculate the angle θ.
（5）
(3) Locate the lighting intensity table and obtain the corresponding intensity value.
(4) Utilize the lighting maintenance coefficient table from the Atlas 19D702-7 to determine the maintenance coefficient.
(5) Calculate the horizontal illuminance.
4. Case Study Sharing
A non-occupied dense area with dimensions of 30 m x 5 m x 3 m (length x width x height) was selected for the layout of the evacuation corridor. The ground-level low illumination requirement for this area is 1 lx. The required number of emergency lighting fixtures was calculated using two different illumination calculation methods.
(1) Average Luminous Efficacy Calculation: Selecting emergency lighting fixtures with a power of 3W, a luminous flux of 360 lm, and a maintenance factor of K=0.7 as determined from a table; calculation using Equation (1) yields a requirement of 3 fixtures.
(2) Point Illuminance Calculation: At a distance of r=5 m, the illuminance value is calculated as =1 lx according to Equation (4). Based on the lighting spacing layout diagram (refer to Figure 3), the lighting is arranged at a spacing of D=10.5 m, which ensures an illuminance of 1 lx in the shadowed area. CAD-based lighting arrangement suggests that three 3W emergency lighting fixtures should be installed in the evacuation corridors.
Figure 3: Lighting Spacing Layout Diagram
Using DIALux evo simulation software, we conducted experimental simulations on the aforementioned cases. Based on the luminaire illuminance distribution within the area, we directly determined whether the selected region met the required ground-level low illuminance. We also verified the calculation results of the two illuminance calculation methods.
4.1 Software Features
DIALux is a highly effective lighting calculation software on the market today, meeting all current lighting design and calculation requirements. DIALux evo enhances modeling and rendering capabilities, making modeling more convenient, rendering more realistic, and calculations more accurate. On one hand, DIALux evo incorporates international lighting standards, providing standardized algorithms and metrics to enhance calculation effectiveness. On the other hand, it collaborates with numerous lighting manufacturers, allowing for the direct integration of manufacturers' complete-featured lamp plug-ins into the software for luminance calculation and lighting distribution simulation, thereby increasing the authenticity of the simulation.
4.2 Simulation Verification
Our company's 3W LED emergency lighting fixtures, with a luminous flux of 360 lm, meet the specified selection requirements for the lighting fixtures. A corridor space of 30m x 5m x 3m (length x width x height) was set up in the DIALux evo software, with the reflectance of the ceiling, walls, and floor within the space set to 0%. The corresponding lighting fixtures were imported into the software, installed in a ceiling-mounted fashion, and positioned 3 meters above the ground. We adjusted the fixture parameters and arranged the fixtures according to different calculation methods, conducting an illumination analysis of the space.
Based on the simulation experiment results, the illuminance values within a 1.25m radius on both sides of the center line of the passage exceed 1 lx, meeting the regulatory requirements (see Figure 4).
Figure 4: Luminance Distribution Chart (Luminance Unit: lx; Length Unit: mm)
5. AnkoRay Luminance Calculation Chart & Lighting Selection
Our emergency lighting products all have complete luminous intensity distribution curves, enabling rapid on-site illuminance simulation with DIALux evo and selection of suitable luminaires to meet requirements.
In addition, our company has developed a lighting luminance calculation chart (as shown in Figure 5), which allows users to directly select based on installation method, lamp power, and installation grade. It automatically calculates the uniform luminance radius values. Moreover, selecting the luminance value between two lamps enables direct calculation of the installation spacing, facilitating clients in quickly and intuitively selecting lighting fixtures.
Figure 5: AnkoRay Emergency Lighting Luminance Calculation Table
Combining the above luminance calculation results and the luminance calculation table for the lighting fixtures, our company's selected lighting fixtures are as follows:
6. Closing Remarks
The article analyzes the requirements for emergency lighting, the selection of luminaires, and the calculation methods. It takes the emergency lighting design of evacuation corridors as an example and verifies the results of the illumination calculation through DIALux evo modeling. The simulation results show that the emergency lighting layout designed through illumination calculation meets the regulatory requirements, with the illumination results presented intuitively. The DIALux evo software can also be used in practical applications for the design of emergency lighting luminaire selection and layout.
Reference
[1] GB50116-2014 "Code for Fire Prevention in Building Design"[S].
[2] GB50034-2013 "Code for Design of Building Lighting" [Standard].
[3] GB51309-2018 "Technical Standard for Fire Emergency Lighting and Evacuation Guidance System" [S].
Yang Guohong. "The Application of DIALux Software in Indoor Lighting Design" [J].
Zeng Qingfeng, Chen Bijun. "Research on Evacuation Lighting Design Based on DIALux?evo Software Simulation"[J].
Ankorri Enterprise Microgrid Design and Application Manual, 2022.05 Edition.
