In this article, Linsheng explores how to implem […]
In this article, Linsheng explores how to implement a safe, regulatory and cost-effective emergency lighting system.
Explosive Eyes for Emergency Lighting The 2015 International Building Code (IBC) specifically requires that the exit road be illuminated when the room or space is occupied. IBC believes that under normal power conditions, the illumination level on the exit path must not be less than 1 fc. This is not the average threshold, but the absolute minimum under normal power conditions. When arranging emergency exit lighting, the path must be carefully analyzed using photometric software to ensure that any point along the exit path is no less than 1 fc. On the other hand, IBC maintains different standards for lighting under emergency power. In the event of a loss of normal power, the lighting provided under emergency power can maintain an average of 1 fc, a minimum of 0.1 fc measured along the exit path of the floor. The allowed level of illumination is reduced to an average of 0.6 fc for the specified duration and is reduced to a minimum of 0.06 fc at the end of the required emergency illumination duration. The maximum and minimum illumination uniformity ratio must not exceed 40:1.
The IBC defines any room that requires two or more exits as spaces that must have properly illuminated aisles, corridors, stairs, and ramps. After defining how to properly illuminate the room, IBC continues to describe how the building must illuminate the entire building. In buildings requiring two or more exit modes, all internal stairs, internal ramps, external stairs, external ramps, exit passages, vestibules and exterior platforms must be automatically illuminated. The utility room in any type of building must also be illuminated, such as electrical equipment rooms, fire command centers, fire pump rooms, generator rooms, and public restrooms over 300 square feet.
The IBC defines the amount of time required for 90 minutes of emergency lighting, whether the backup power source is a centralized battery system, a local unit or a field generator.
NFPA 101 requirements
NFPA 101: Life Safety Code, 2018, details the requirements for export lighting. First, NFPA outlines that lighting should be continuous during the time that residential conditions require the use of an exit facility. The specification continues to state that artificial lighting should be used in the locations and time periods required to maintain illumination at a minimum standard.
According to the definition of NFPA 101, for emergency systems, lighting equipment should be arranged to provide initial illumination, which should be no less than 1.0 fc on the floor level exit path and no less than 0.1 fc at any point. At the end of the specified 90-minute period, the illuminance level should be allowed to fall to an average of not less than 0.6 fc. Similar to IBCs, the ratio of maximum to minimum illumination must not exceed 40:1.
Regarding automatic lighting control, NFPA 101 describes how and when to control emergency exit lighting. The following criteria must be considered when specifying lighting control equipment.
Lighting control equipment must be provided to turn on the emergency exit light after losing normal power.
Depending on the requirements of the new building, if a fire alarm panel is provided, the lighting control equipment must be activated by the building fire alarm system.
As photoluminescent signs become more prevalent in building design, lighting control equipment must not turn off the illumination on which any photoluminescent signage depends.
The lighting control unit must also not turn off any battery-powered lights.
In general, when using energy-efficient nodes, clocks, and sensors, designers must ensure that these devices do not compromise the continuity of the emergency lighting system.
The clock and lighting control panel must be carefully specified to prevent the circuit from being stuck in the "off" or open position, as such equipment should be specified to provide fail-safe "on" or off control conditions in the absence of power.
It is important to understand the level of emergency exit lighting required on the route. Placing lights along the walls in the stairwell may pose a challenge to projecting the right amount of light in these areas. Some light rendering software may also make it difficult to properly simulate the lighting level of a staircase. Engineers who place lighting should be strategic when specifying the height of the fixture installation to ensure proper lighting levels are achieved.
Similar to IBC, NFPA 101 defines emergency lighting outlets as stairs, aisles, corridors, ramps, escalators, and access to exits. Lighting at the exit includes stairs, aisles, ramps, sidewalks and escalators leading to public roads.
When the lighting method relies on switching from one source to another, the NFPA requires a delay of no more than 10 seconds. This code excerpt most commonly refers to the dependence on generator power and the ability to automatically start the generator power and transfer the load over the required time range. After a normal power failure, the emergency lighting must be able to provide 90 minutes of illumination, similar to the requirements of the IBC.
NFPA 70 requirements
NFPA 70: National Electrical Code (NEC), 2017 edition, defines the requirements for emergency systems. Chapter 700 outlines the circuit wiring and power supplies associated with the required emergency system. Like other regulations already discussed, NEC also requires emergency batteries to provide and maintain loads for at least 90 minutes. NEC further stated that the battery voltage supplied to the unit fixture should not be lower than 87.5% of the normal operating voltage.
Emergency lighting factor
Linsheng stated that the layout of emergency lighting is a key design component of the emergency lighting system. The definition of emergency lighting is the light that will illuminate the outlet when the normal circuit is interrupted. There are many different options and factors to consider when arranging emergency lighting.
One factor to consider is the type of lamp that will be used. LED luminaires have swept the market in the past five years, and although other types of luminaires should be considered, LEDs will continue to be the backbone of emergency lighting. LEDs have a long life expectancy and can keep equipment maintenance-free for up to 50,000 lamp hours. Similarly, the color temperature of LED lamps should not be a problem; LED lamps are available in a variety of color temperatures to suit the application. One of the main advantages of LED lighting is efficiency. Usually, this is an unappreciated feature when considering an alternate emergency power supply. Regardless of whether the luminaires to be specified are backed up on batteries, generators or other power sources, the efficiency of the LEDs allows the designated engineer to adjust the size of those emergency power systems in a more reasonable manner.
Some major failures of LED lights are replacing them. Although the long life of LEDs is a huge benefit, it can be seen as a disadvantage when approaching the life expectancy of a luminaire, and replacement is a major task. Whether the driver or circuit of the LED lamp fails or the LED lamp only exceeds its expected life, replacing the lamp on some LED luminaires is more difficult and laborious than replacing the fluorescent lamp. This should be taken into account when arranging emergency lighting, and more considerations should be taken when selecting fixtures, as some fixtures may have unique lighting options that help maintenance personnel maintain proper illumination throughout the life of the building. We also recommend that you carefully check the warranty and the expected value of the lamp, because in many cases, the life expectancy of cheaper LED products entering the market is not as expected, which brings a bad reputation to LEDs and makes maintenance personnel difficult to maintain. The product being designed. Illumination when the luminaire fails prematurely.
Emergency Power Supply
There are many different emergency power sources to consider when designing an emergency lighting system. The most common type of system used in budget-friendly projects is the two-headed emergency force, sometimes referred to as the "bug eye" (see Figure 1). As described by NEC, these fixtures make it easy for contractors to connect them to local branch circuits without the need to add a large amount of additional emergency infrastructure. These devices connect to the local branch circuit in the event of a power failure and illuminate when normal power is lost. The internal battery illuminates the double head for emergency lighting. One of the disadvantages of these fixtures is that each fixture requires testing and maintenance, resulting in many test and maintenance points. Even when the test switch indicator lights initially, these luminaires must be thoroughly tested to verify that the luminaire is capable of outputting the desired level of illumination while maintaining the proper voltage to the luminaire for the entire specified time range.
An alternative to specifying a dual-head emergency battery pack is to provide an emergency lighting uninterruptible power supply (UPS). The benefit of specifying and installing an emergency lighting UPS is that there is a central battery system that can be used to replace many of the luminaires dispersed throughout the facility. If applied correctly, the emergency lighting UPS system can be as cost effective as installing a dual-head emergency battery pack to provide emergency exit lighting. Many times, the cost of purchasing many double-headed emergency battery packs can offset the cost of purchasing a central emergency lighting UPS. From a cost perspective, the success or failure between the battery unit and the central UPS usually depends on the conduit, wiring and switching scheme of the emergency light. These factors depend on the type of space and how it is laid out. How the space is configured will depend on how the lights are switched. The large open space allows for a UPS-type system because it simplifies the circuit and has many small independent switch areas that require emergency lighting.
Using emergency generators as a power source is another consideration, sometimes depending on the type of occupancy. Whether it is natural gas, diesel or propane, one of the main benefits of having an on-site emergency generator is that the delivered power can last longer than any battery system. Connecting the generator to the natural gas supply provides a highly reliable source of energy to keep the generator running compared to battery power typically used for 90 minutes of emergency lighting. It should be noted that, according to NEC, a generator with an acceptable authority (AHJ) means that some measures should be provided to automatically start the generator in the event of a normal power failure and automatically transfer the load of all required circuits. One of the main drawbacks of natural gas may be the lack of reliability during a real natural disaster. Consideration must be given to maintaining fuel source connections during disasters, which is why parts of the country's seismic zone may cause potential damage to underground pipelines and therefore require alternative fuel sources, such as diesel. Diesel is another popular source of fuel, but even diesel has its drawbacks. Large diesel daily storage tanks are designed to store fuel to maintain electricity for several days. Designated engineers should consider factors such as fuel life. Long-term storage of large amounts of diesel can cause problems because the fuel degrades over time. Having a refueling contract is another component of discussions with customers to ensure that appropriate measures are taken for emergency lighting.