What is an Emergency Lighting Inverter?
An emergency lighting inverter is a centralized power system that continues operating during a power outage, supplying power to emergency lighting and exit signs in a building. It charges a battery pack using utility power and converts stored DC energy to AC voltage when utility power is unavailable.
Emergency lighting is a critical safety requirement, and a reliable power system is essential to ensure it functions properly. The traditional approach to lighting, with individual battery units in each fixture, can be complicated.
How Does an Emergency Lighting Inverter Work?
Normal Operation: Charging
An inverter keeps the battery pack fully charged and monitors the building’s power supply. All connected fixtures are supplied with normal power.
Power Failure: Switching to Battery Pack
In the event of a power outage, the inverter automatically switches to battery power. It converts DC to AC and supplies power to the lights and exit signs for the rated period. This transfer is supposed to happen very quickly.
Power Restoration: Switching Back
When utility power is restored, the inverter switches back to the normal power source and recharges the batteries.
What Are the Main Components of an Emergency Lighting Inverter?
Components of an emergency lighting inverter include:
- UPS module – it is responsible for managing the power.
- Battery module and battery assembly – it stores the energy needed to power the lighting fixtures during the outage.
- Battery charger – it charges the battery in case utility power is available.
- Output power transformer – it prepares the output to meet the requirements of lighting fixtures.
- Display and controls – they provide information about the current state of the system and allow performing tests and troubleshooting.
Types and Sizes of Emergency Lighting Inverters
Inverters are usually grouped by how much power they can deliver to the emergency lighting load.
| Type | Typical Rating | Typical Use |
|---|---|---|
| Micro inverter | About 25–35W | Small spaces with a few fixtures |
| Mini inverter | About 100–350W | Small to mid-size areas and individual zones |
| Mid-size and modular inverters | 350W and above | Larger buildings; modular systems scale up in single, two, split, and three-phase configurations |
Isolite offers the full range, from micro through modular inverters.
Why Emergency Lighting Is Required by Codes
The purpose of emergency lighting is to maintain visibility and enable egress during power outages, fires, or other emergencies. The requirements come from the building and fire codes applicable in your area; they often reference NFPA 101 (Life Safety Code), the International Building Code, and NFPA 70 (National Electrical Code). Usually, the lighting system is required to illuminate the way for at least 90 minutes. The equipment should be UL 924-listed, and there may be additional requirements imposed by the local jurisdiction, so you should consult the AHJ.
Emergency Lighting Inverter vs. Battery Packs
| Factor | Central Inverter | Individual Battery Packs |
|---|---|---|
| Battery location | One central, accessible location | Inside or beside every fixture |
| Maintenance and testing | Centralized | Fixture by fixture |
| Battery replacement | One battery system to service | Many small batteries across the building |
| Battery replacement | One battery system to service | Many small batteries across the building |
| Best for | Medium to large buildings, accessible service | Small spaces or simple retrofits |
For a deeper cost comparison, see Isolite’s Chalk Talk webinar on inverters vs. battery packs.
Advantages of Using an Emergency Lighting Inverter
- Easy Installation, Maintenance, Repairs, and Replacement
By consolidating batteries and electronics in one place, a technician will need to service only one system instead of reaching out to all fixtures. - Scalability and Upgradability
A modular design allows capacity upgrades in response to changes in building or lighting fixture configurations. - Automatic Testing, Alerts, and Reports
Modern inverters can perform automatic self-tests and send alerts and reports to building management, helping ensure compliance with codes and minimize manual testing. - Cost-effective Features through System Lifespan
A centralized emergency lighting system reduces the number of elements to inspect and replace, potentially lowering the total cost of ownership over the installation’s lifetime.
How to Choose an Emergency Lighting Inverter
- Load calculation: sum up the power rating of all fixtures and exit signs in the system.
- Determine the runtime: most of the codes require at least 90 minutes of runtime.
- Voltage and Phase Alignment: Choose the appropriate configuration: single-phase, two-phase, split-phase, or three-phase.
- Evaluate Operating Environment: temperature, location, and seismic factors will influence the installation method.
- Planning, Monitoring, and Maintenance: decide on the necessity of remote monitoring and plan future maintenance.
- Comply with the Requirements: check the listing and local requirements, including BAA compliance for federal projects.
Testing and Maintenance Requirements
There is a requirement to test the emergency illumination regularly. According to NFPA 101, the usual requirement is a short monthly test and a full-duration annual test, where the results should be kept in records for the inspector. Inverters equipped with self-test capabilities can automate most of the procedure and alert to any problems before they occur. Isolite also provides inverter service to make sure the system operates as intended.
FAQ on Emergency Lighting Inverters
What is the use of an emergency lighting inverter?
It supplies backup power to the emergency lighting fixtures and exit signs from the battery pack, converting DC power to the required AC voltage.
What is the runtime of an emergency lighting inverter?
Most of the systems are designed to operate for 90 minutes, the minimum required by the codes. Depending on battery capacity and load, some systems can operate even longer.
Is the exit sign supposed to have an inverter?
Not necessarily. They can be operated either from internal batteries or from a central inverter. The latter option is preferable when the building has numerous signs and fixtures that should be powered from a single location.
What is the difference between an inverter and a UPS?
Both of the devices use batteries to power the equipment. While an inverter is specifically designed and listed for the life-safety lighting load and code-required runtime, a typical Uninterruptible Power Supply (UPS) is designed for electronics such as computers or servers.
Can an inverter power normal light fixtures?
Yes. The central inverter can supply normal fixtures on the emergency circuit and serve as emergency lighting in the event of a power failure.
Consultation with Emergency Lighting Specialists
If you are planning an emergency lighting installation or replacement of the existing system, it is worth considering the full range of emergency lighting inverters, as well as inverter training and services. You can find a representative or get help with inverter issues by calling 800-967-5573.
