NFPA 110 Level 1 vs Level 2 - Classification, Type and Class Explained

NFPA 110 sets the rules for how emergency and standby power systems must work inside a building. Facility managers and electrical contractors often confuse the level, type, and class ratings that the standard assigns to every installation. In this blog, we will explain the fuel, testing, and installation rules that apply to each system type.

What the NFPA 110 Standard Covers

The NFPA 110 standard applies to permanently installed emergency & standby power supply systems. It covers the generator set, controls, transfer equipment, supervisory devices, and the electrical & mechanical auxiliary systems that keep the plant running. The rules follow the equipment from the day of commissioning through every year of service.

One point causes constant confusion on site. The standard never decides which buildings need an emergency source in the first place. That decision comes from NFPA 101, the Life Safety Code, NFPA 99 for healthcare facilities, and applicable local building codes. The NFPA 110 standard for emergency and standby power systems then outlines how the equipment should perform and how frequently it must be tested.

NFPA 110 Classification System Explained

The NFPA 110 classification rests on three separate parameters. Every installation carries all three labels at once, so a hospital plant might read as a Level 1, Type 10, Class 48 system. Each label answers a different design question.

Level Shows the Consequence of a Failure

Level 1 applies wherever a failure could cost a human life or cause a serious injury. Level 2 applies wherever a failure carries less risk to life and safety. The design team sets the level first, because that single choice drives fuel capacity, room construction, and the test schedule.

Type Sets the Maximum Restoration Time

Type states how many seconds the plant may take before it restores acceptable power to the load.

1. Type U covers an uninterruptible supply and suits critical computer equipment.

2. NFPA 110 Type 10 restores power within ten seconds, which fits emergency lighting and life safety loads.

3. NFPA 110 Type 60 allows 60 seconds and serves the less critical parts of a building.

4. NFPA 110 Type 120 allows 120 seconds and mainly protects equipment.

Type M covers a manual start with no time limit, such as a portable set.

Class Defines the Minimum Runtime at Full Load

The NFPA 110 Class ratings state the number of hours the plant must hold at full rated load without a refill.

1. Class 0.083 covers five minutes and normally applies to a UPS.

2. Class 0.25 covers fifteen minutes.

3. Class 2 covers two hours.

4. Class 6 covers six hours.

5. Class 48 covers 48 hours.

6. Class X covers any other duration that the application, the governing code, or the user sets.

NFPA 110 Level 1 vs Level 2 Requirements

A clear NFPA 110 Level 1 vs. Level 2 comparison helps a facility budget for fuel, testing, and room construction well before the equipment arrives. The two categories share the same equipment families, yet they carry very different obligations.

Loads That Fall Under NFPA 110 Level 1

NFPA 110 Level 1 covers the loads that keep people safe while the normal supply stays down.

1. Emergency lighting keeps the means of egress visible during an outage.

2. Fire detection and alarm systems stay live on the emergency source.

3. Fire pumps draw their power from the same supply.

4. Elevators in high-rise buildings continue to move occupants and firefighters.

5. Critical ventilation and smoke control equipment clears escape routes.

6. Healthcare facilities keep the critical branch under power.

7. Emergency communication systems reach every occupant in the building.

Loads That Fall Under NFPA 110 Level 2

NFPA 110 Level 2 covers the loads that protect property, comfort, and business continuity rather than life.

1. The building keeps heating and refrigeration equipment running to protect stock and pipework.

2. Routine communication systems stay online for staff and visitors.

3. Sewage disposal equipment continues to operate.

4. Industrial processes avoid a costly and slow restart.

5. Data processing systems hold their records and their uptime.

Major Differences Between the Two Levels

The following table outlines key NFPA 110 facility requirements for both Level 1 and Level 2 systems. These are commonly used as legally required standby systems in emergency and critical power applications.

Table showing how requirements change between a Level 1 and a Level 2 emergency power supply system.

Components of an Emergency Power Supply System

A complete emergency power supply system (EPSS) brings together several groups of equipment that must work as one unit.

Energy Converters

1. The prime mover runs on a diesel, natural gas, or dual-fuel engine.

2. The alternator turns that mechanical energy into usable electrical power.

3. The cooling system uses either a radiator or a heat exchanger.

4. The exhaust system carries gases away through mufflers and emission controls.

5. The starting system depends on batteries and a matched charger.

Transfer Equipment

1. An automatic transfer switch (ATS) moves the load between the normal source and the emergency source.

2. A bypass isolation switch lets a crew service the switch without an interruption.

3. A load bank connection allows a full test without any building load.

4. Gear for paralleling ties several generators onto a single bus.

Controls and Annunciation

1. Local and remote annunciator panels show the live status of the plant.

2. Automatic starting controls crank the engine the moment the normal source drops.

3. Battery monitors report a weak cell long before it causes a failed start.

4. Remote monitoring links the plant to a central station or a service partner.

5. Load management controls shed the lower priority circuits when demand climbs.

Fuel System Components

1. Redundant fuel pumps serve a Level 1 installation.

2. Primary and secondary filters clean the fuel before it reaches the engine.

3. Water separators pull moisture out of the stored fuel.

4. Fill connections stay accessible so a tanker can refuel the site during an emergency.

Maintenance and Testing Requirements

A generator earns its rating only through a disciplined routine. The standard sets both the frequency and the load for every test.

Test Schedule for a Level 1 System

1. The weekly test runs the engine for five to ten minutes with no load applied.

2. The monthly test runs for 30 minutes on whatever load the building offers at that moment.

3. The annual test runs for four hours at 100 percent of the nameplate rating.

4. The triennial test repeats a four-hour run every 36 months with a load bank in place.

5. The monthly transfer test moves the actual load through one complete cycle.

Routine Maintenance Tasks

1. A weekly visual inspection covers every system in the room.

2. Oil and filter changes follow the manufacturer's schedule or the result of an oil analysis.

3. The coolant system needs an annual flush and refill.

4. Battery care includes a monthly specific gravity test.

5. Annual fuel testing confirms the quality of the diesel in the tank.

6. A written log records every test and every maintenance task for the authority having jurisdiction.

NFPA 110 Generator Installation Requirements

Location and Environment

1. An indoor NFPA 110 generator sits in a separate room with proper ventilation.

2. A Level 1 installation needs a 2-hour fire separation from the rest of the building.

3. A Level 1 room holds a minimum of 40 degrees Fahrenheit, and a Level 2 room holds a minimum of 32 degrees Fahrenheit.

4. Ventilation supplies combustion air and removes the heat that the engine gives off.

5. The layout leaves at least 3 feet of working space around the equipment.

6. An outdoor set needs a weather enclosure that matches the assigned Type rating.

Electrical Installation

1. Separate feeders serve the emergency loads across the building.

2. Proper grounding and bonding follow the rules for a separately derived source.

3. Surge protection devices guard the sensitive equipment on the emergency branch.

4. Selective coordination of overcurrent devices stops a local fault from tripping the whole system.

5. A remote annunciator sits in a location that staff attend at all times.

6. The plant links to the building management platform for continuous visibility.

Fuel Systems and Storage Rules

Fuel Storage Capacity

1. The main tank holds 133 percent of the fuel that the required runtime needs, which builds in a safety margin.

2. The day tank holds at least one hour of supply at full load.

3. An automatic transfer pump refills the day tank from the main tank.

4. The fuel meets the relevant ASTM standard for diesel or natural gas quality.

5. A fuel polishing routine protects diesel that sits in storage for long periods.

6. Dual fuel connections give the site a natural gas backup wherever a supply exists.

Final Thoughts on NFPA 110 Level 1 vs Level 2

NFPA 110 provides a structured framework for emergency and standby power systems. Level, Type, and Class each define a different aspect of system performance. These requirements cover fuel storage, testing, installation, and maintenance. Together, they support reliable operation when normal power fails and help protect people, equipment, and essential building functions.

At Nixon Power Services, we offer Kohler generators and power solutions designed to support a wide range of standby and emergency power applications. Our team provides generator installation in Oklahoma City, along with generator selection, maintenance, and ongoing service to help keep your power system ready when you need it most.

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