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What is Emergency Lighting Circuit Diagram ?

Emergency lighting is a type of lights that can effectively illuminate and display exit passageway or can continue to work without interruption when the normal lighting power supply fails,  Widely used in public places where can lighting without intermittent . The emergency lighting fixture is composed of a light source, a light source driver, a rectifier, an inverter, a battery pack, a logo lamp housing something like that.

Here is a circuit diagram of an emergency lighting made with LES.

The circuit operation of the device is shown in Figure 1. Power outages are a recurring thing, but in some cases power outages are not allowed (such as ongoing surgery). The circuit designed with LSE is simple and fully automated. When there is 220V AC power, the illumination lamp H1 is lit, and the ④ pin of the LSE output with high level output, the Transistor VT is turned off, and the relay J is in a release state, so the DC lamp H2 is not lit. Once power cut, H1 goes out, and the LSE’s ④pin outputs a low level. At this time, the Transistor VT is conduction, the relay J is pulled in, the power of the illumination lamp H2 is connect, the H2 is automatically lit, and the transition between the two lamps is almost no break Intermittent.

Emergency lighting is still an important product required in against fire safety measures. In the event of an emergency, such as an earthquake, fire or circuit failure, the power supply is suddenly interrupted and all light sources have ceased to operate. At this point, it must provide reliable illumination immediately and indicate the direction of evacuation and the location of the emergency exit, in order to ensure the people who are in dark can evacuate

An Emergency Lighting Circuit Diagram


An emergency lighting circuit diagram depicts the electrical connections and components of a system that provides backup illumination during power outages. Emergency lighting is essential for building safety by providing low level lighting to aid in emergency egress when normal lighting fails.

The emergency lighting circuit includes batteries, chargers, indicators, controls, and the specialized light fixtures needed to provide emergency lighting in buildings and public spaces as required by electrical and fire safety codes. Understanding emergency lighting circuits through their circuit diagrams is important for installation, inspection, and maintenance.

This article provides an overview of the key components and typical wiring diagrams used in emergency lighting installations.

Purpose of Emergency Lighting

Emergency lighting serves a vital safety function in buildings:

  • Illuminates exit paths to allow occupants to evacuate safely during emergencies or power loss.
  • Provides minimum illumination for critical areas like stairwells, aisles, corridors, ramps, and passageways.
  • Allows emergency responders to access and navigate a building in blackout conditions.
  • Reduces panic by providing some lighting during sudden power failures.
  • Serves as a backup to normal lighting system in case of electrical failure.
  • Mandated by national and local electrical, building, and fire codes for most public buildings. Exceptions sometimes made for small residential spaces.

Proper emergency lighting installation is crucial. The circuitry must be reliable and wire correctly to fixtures intended for emergency use.

Key Components of Emergency Lighting Circuits

A typical emergency lighting system consists of the following major components:

Backup power source – Usually rechargeable sealed lead acid batteries. May have 30 minute to 3 hour runtime.

Battery charger – Maintains batteries in a fully charged state for immediate use when needed. Connects to line voltage.

Control unit – Senses loss of external power and automatically switches to batteries to power emergency lighting.

Status indicators – LEDs or audible alarms indicate external power loss, battery state, faults.

Emergency lighting fixtures – Illuminate when normal power fails. Contain backup ballasts and lamps.

Wiring and conduit – Transports external line power and connects fixtures to control units. May include junction boxes.

Understanding the function of each component is key to properly interpreting emergency lighting circuit diagrams.

Typical Emergency Lighting Wiring Diagram

Here is a typical wiring diagram for a basic emergency lighting installation:

This diagram shows 3 key elements of the circuit:

1. Line Input

External 120/277V AC supply powers the charger and some controls. Ground connection required. Line input may have overcurrent protection via circuit breaker.

2. Battery and Charger

Batteries connect to charger module. Charger keeps batteries in ready state by providing regulated DC float voltage charge. Charger taps line input power.

3. Emergency Lighting Fixtures

Fixtures contain internal backup batteries or lamp heads designated for emergency use. Connected to central control unit via switched circuit for detecting loss of external power.

Let’s look at the key components and connections in more detail.

Chargers and Batteries

  • Chargers maintain emergency light batteries in a fully charged state and prevent overcharging. Accept universal line voltage input.
  • Batteries used are typically sealed lead acid. Sizing depends on fixture runtime and load requirements.
  • Switchover to battery when line voltage drops below ~80-90% occurs in milliseconds to avoid any lighting interruption.
  • Batteries generally have a 3-5 year lifespan and must be replaced periodically. Chargers may also need replacement over time.
  • Battery voltage is usually 6V, 12V, or 24V DC to operate lamp heads and internal circuitry.

Proper battery maintenance and testing is crucial to ensure emergency lighting system activates reliably when needed.

Control Units and Status Indicators

  • Control units manage switching between external line power and internal DC battery power. Auto-sensing line loss.
  • Audible alarms and LED indicators show system status – AC/battery mode, faults, charger issues, etc.
  • Optional self-testing feature runs periodic discharge tests to validate battery charge and switchover functioning.
  • Detailed diagnostics for troubleshooting available from some microcontroller-based units.
  • Status indicators must be suitably placed for easy inspection by facility maintenance personnel.

Controls and alarms provide confidence in system operation and help catch issues before an emergency occurs.

Emergency Lighting Fixtures

There are 2 main types of emergency lighting fixtures:

Unit Equipment – Complete self-contained emergency lighting solution with integrated battery, charger, and lamps or LED arrays. Available for both interior and exterior fixture applications. Designed for easy installation and maintenance.

Remote Fixtures – Lamps heads or LED arrays are connected by wiring to a centralized control unit and battery supply. Allows using normal lighting fixtures for emergency use to save cost. Requires compatible fixture compatibility.

Proper aiming, placement, and spacing of emergency lighting fixtures following lighting codes is necessary to adequately illuminate emergency egress paths.

Emergency Lighting Wiring

  • Line voltage wiring feeds AC supply to chargers and control units. Follows national and local electrical codes.
  • Class 1 rated wiring used between central batteries/controls and remote lamp heads.
  • Low voltage DC wiring used internally within self-contained emergency lighting units.
  • Neutral line connects chargers, controls, and any status indicators.
  • Grounding via connection to earth ground and metal conduit improves safety and noise rejection.
  • Separate conduit recommended for emergency lighting wiring. Do not mix with other building wiring.

Properly installed and segregated wiring with suitable conductors enables reliable operation during emergencies.

Additional Emergency Lighting Features

Some additional features sometimes incorporated into emergency lighting circuits include:

  • Dedicated transformers to provide line isolation and optimal voltage to the charging system.
  • Backup generators as a secondary source when battery capacity is exceeded by long outages.
  • Remote trouble indication panels to centrally monitor system status.
  • Integration with building management systems for centralized control and monitoring.
  • Zone wiring to group fixtures in different areas on separate circuits. Improves survivability.
  • Emergency lighting incorporated into exit signs to provide egress path illumination.

While not required in simple systems, these features improve robustness, monitoring, control, and survivability.

Typical Emergency Lighting Specifications

To size and specify an emergency lighting system properly, some key specifications need to be defined:

  • Illumination level provided – Usually 10-20% of normal lighting levels. Needs to meet codes for environment.
  • Runtime on battery – 30 minutes, 1 hour, 2 hours etc. Dictates battery capacity needed.
  • Battery type – Sealed lead acid common. Nickel cadmium for cold environments. Lithium for extended runtimes.
  • AC supply voltage – 120V or 277V are typical, but many chargers support both.
  • Charger amperage rating – Determines how long batteries take to recharge after outage.
  • Operating temperature range – Most systems work from 0°C to 40°C. Special batteries needed for extreme cold/hot.
  • Status indicators and diagnostics included
  • Certifications – UL 924, NFPA 101 Life Safety Code, local codes.

Properly sizing and specifying the emergency lighting system based on these parameters ensures that the installation meets all necessary performance, runtime, and code compliance requirements.

Inspecting and Testing

Regular inspection and testing of emergency lighting systems is vital to validate proper performance. Some recommended actions include:

  • Monthly visual checks of status indicators to verify system health.
  • Annual discharge test by disconnecting line voltage and operating fully on battery for programmed runtime.
  • Testing indication alarms and alerts when faults are simulated.
  • Checking charger voltage and current settings are properly calibrated.
  • Validating batteries not nearing end of useful life. Replacement as needed every 3-5 years.
  • Inspecting electrical connections are tight and free of corrosion.

Documenting and timestamping inspection results provides records for regulators. Issues uncovered during testing can then be corrected proactively.


  • Emergency lighting provides essential illumination during power failures to aid in safe building evacuation.
  • Key components include batteries, chargers, controls, status indicators, and emergency lighting fixtures.
  • Wiring diagrams depict connections between line input, charging system, control units, and fixtures.
  • Estimating illumination levels and runtimes allows proper sizing and selection of the system.
  • Regular inspection testing validates that the emergency lighting system functions reliably when needed.

Following good emergency lighting design, installation, and maintenance practices ensures building occupant safety when normal lighting fails.


What battery backup time is required by code for emergency lighting?

Most building codes require a minimum of 90 minutes of runtime for emergency lighting on battery backup. Healthcare and high-rise buildings may mandate up to 3 hours of backup capacity.

Where should emergency lighting fixtures be located?

Fixtures must be located along exit pathways and stairwells to illuminate egress routes. Spacing and placement should follow lighting level requirements in local codes.

How often should emergency lighting systems be tested?

Monthly visual inspections and annual discharge tests for full runtime are recommended. Testing should validate that status indicators function and designed lighting levels are achieved.

What wiring should be used for emergency lighting circuits?

Line voltage wiring should follow normal electrical code requirements. Low voltage wiring between controls and remote fixtures should use Class 1 rated conductors. Separate conduit is recommended.

What are common emergency lighting failure points?

Batteries failing to hold charge and aging chargers are common failure causes over time. Wiring faults, uncalibrated controls, and improper maintenance also lead to malfunctions. Testing identifies issues before an emergency.




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