Emergency and Exit Lighting
Summary
Emergency and exit lighting is unit equipment with batteries, emergency LED drivers inside normal luminaires, central inverters, or generator-fed circuits that keep egress paths lit and exit signs illuminated when normal power fails. It is a life safety system, so power source, transfer, duration, illuminance along the path, testing method, and coordination with normal lighting controls must be designed with the electrical engineer.
Cols
Terminology
- Unit equipment: emergency fixture with self-contained battery, charger, and transfer switch ("bug-eye" units and combo exit/emergency units)
- Emergency LED driver: battery pack inside or beside a normal luminaire that powers it on power loss
- Central inverter: battery system serving many normal luminaires on emergency circuits
- Generator-backed emergency branch: emergency circuits fed through a transfer switch from a generator
- Bypass / shunt relay (UL 924 relay): device that forces controlled luminaires on during power failure
- Self-diagnostic / self-testing: units that run automatic periodic tests and show status
- Remote heads: lamp heads powered from a separate battery unit
- Internally illuminated exit sign: LED sign listed for exit use
- Photoluminescent exit sign: sign charged by ambient light; no wiring
- Path of egress: route measured for emergency illuminance
Standards
Ratings
- 90-minute emergency operation is the common duration for batteries and units
- LED emergency drivers and units transfer to battery within 10 seconds of power loss
- Self-diagnostic units run short automatic tests at least every 30 days and indicate faults
- Damp, wet, and cold-rated units for exterior exit discharge
Test standards
- UL 924: emergency lighting and power equipment
- UL 1598 and UL 8750: luminaires and LED equipment
- NFPA 70 and NFPA 101: installation and testing provisions as adopted
Components
- Exit signs: single or double face, edge-lit or stencil, red or green per jurisdiction
- Battery units and remote heads: stairs, corridors, electrical rooms
- Emergency drivers: integrated in downlights, troffers, and linear fixtures
- Inverters: central systems for many fixtures or architectural lighting
- Relays and controls: UL 924 relays to override dimming and switching
Detailing
- Lay out emergency fixtures from a photometric calculation along the egress path, not by fixture count
- Coordinate emergency lighting with normal lighting controls so emergency fixtures are not left off or dimmed during power loss
- Locate exit signs for visibility from all directions of travel, including floor-level signs where required
- Use emergency drivers in architectural fixtures to avoid visible battery units in finished spaces
- Specify self-diagnostic units to reduce manual testing
- Place exterior emergency lighting at exit discharge doors
Uses
Specific uses
- Corridors, stairs, and exit passageways
- Assembly spaces and large open areas
- Electrical, fire pump, and generator rooms
- Public restrooms and windowless rooms
- Exterior exit discharge paths
Pros and cons
Pros
- Unit equipment is simple and needs no generator
- Emergency drivers keep finished ceilings clean
- Central inverters simplify testing and maintenance
- LED exit signs use little power and last long
Cons
- Batteries need replacement every few years
- Testing burden without self-diagnostic or central monitoring
- Unit equipment can look utilitarian
- Control integration errors can leave paths dark
Manufacturing and cost
Construction
- Units and signs wired to unswitched local circuits or emergency branch circuits
- Emergency drivers installed in luminaires with test switches
- Commissioned with a power-failure test and illuminance check
Main manufacturers and suppliers
- Acuity Brands (Lithonia emergency)
- Signify (Bodine emergency drivers)
- Cooper Lighting Solutions (Sure-Lites)
- Hubbell Dual-Lite
- Barron Lighting Group (Exitronix)
Trade association: National Electrical Manufacturers Association.
Typical costs
- Exit sign, installed: about $120 to $250 per sign for typical installs; units range from $20 to $450
- Installation labor alone: about $75 to $420 per sign
Sources
- IEEE TechNav: emergency lighting and UL 924, Emergency lighting | IEEE Technology Navigator
- Signify Bodine: codes, standards, and requirements, Codes and planning | Bodine
- Minnesota Department of Health: emergency lighting testing guide, https://www.health.mn.gov/facilities/regulation/engineering/lscbatopliting.pdf
- Kansas State Fire Marshal: emergency light testing log, https://firemarshal.ks.gov/DocumentCenter/View/1558/Emergency-Light-Testing-Log
- PacLights: choosing exit signs with emergency lights, Choosing the Right exit signs with emergency lights: What Experts Recommend - PacLights
- Wikimedia Commons: NFPA 101-1929 - Internally Lit Exit Sign - Red.svg, by National Fire Protection Association (Public domain), https://commons.wikimedia.org/wiki/File:NFPA_101-1929_-_Internally_Lit_Exit_Sign_-_Red.svg