NFPA 110: Emergency & Standby Power Systems
Standards for generators, transfer switches, and emergency power supply systems
Overview
NFPA 110 is the Standard for Emergency and Standby Power Systems, establishing requirements for the performance of emergency power supply systems (EPSS). This standard covers the installation, maintenance, operation, and testing of systems that provide an alternate source of electrical power in buildings and facilities when the normal electrical power source fails.
Critical Note: NFPA 110 does not determine which facilities require emergency power. Those requirements come from NFPA 101 (Life Safety Code), NFPA 99 (Healthcare Facilities), and local building codes. NFPA 110 specifies how to properly install and maintain the systems once required.
The standard applies to permanently installed emergency and standby power systems including generators, transfer equipment, controls, supervisory equipment, and associated electrical and mechanical auxiliary systems.
Level, Type, and Class Classifications
NFPA 110 uses three parameters to classify Emergency Power Supply Systems:
Level - Application Criticality
- Level 1: Where failure could result in loss of human life or serious injuries
- Level 2: Where failure is less critical to human life and safety
Type - Restoration Time
| Type | Restoration Time | Typical Application |
|---|---|---|
| Type U | Uninterruptible (UPS) | Critical computer systems |
| Type 10 | 10 seconds | Emergency lighting, life safety |
| Type 60 | 60 seconds | Less critical systems |
| Type 120 | 120 seconds | Equipment protection |
| Type M | Manual (no time limit) | Portable generators |
Class - Runtime Duration
- Class 0.083: 5 minutes (UPS systems)
- Class 0.25: 15 minutes
- Class 2: 2 hours
- Class 6: 6 hours
- Class 48: 48 hours
- Class X: Other time as required (typically 72-96 hours)
Level 1 vs Level 2 Requirements
Level 1 Systems (Life Safety Critical)
- Emergency lighting for means of egress
- Fire detection and alarm systems
- Fire pumps
- Elevators for high-rise buildings
- Critical ventilation systems (smoke control)
- Healthcare facility critical branches
- Emergency communication systems
Level 2 Systems (Less Critical)
- Heating and refrigeration systems
- Communication systems (non-emergency)
- Sewage disposal
- Industrial processes
- Data processing systems
Key Differences in Requirements
| Requirement | Level 1 | Level 2 |
|---|---|---|
| Fuel Storage | 96 hours typical | As specified |
| Testing Frequency | Weekly/Monthly | Monthly |
| Room Separation | 2-hour fire rating | 1-hour typical |
| Temperature Control | 40°F minimum | Per manufacturer |
System Components
A complete EPSS includes these essential components:
Energy Converters (EPS)
- Prime Mover: Diesel, natural gas, or bi-fuel engines
- Generator: Alternator producing electrical power
- Cooling System: Radiator or heat exchanger
- Exhaust System: Mufflers and emissions controls
- Starting System: Batteries and charging system
Transfer Equipment
- Automatic Transfer Switch (ATS): Transfers load between normal and emergency power
- Bypass Isolation Switch: Allows ATS maintenance without interruption
- Load Bank Connection: For testing without building load
- Paralleling Gear: For multiple generator systems
Controls and Annunciation
- Local and remote annunciator panels
- Automatic starting controls
- Battery monitoring systems
- Remote monitoring capabilities
- Load management controls
Fuel Systems & Storage
Fuel Storage Requirements
- Main Tank Capacity: 133% of required runtime (safety factor)
- Day Tank: 1 hour minimum supply at full load
- Fuel Transfer: Automatic refill from main tank
- Fuel Quality: ASTM-compliant diesel or natural gas
- Fuel Polishing: Recommended for long-term storage
- Natural Gas: Dual fuel connections where available
Fuel System Components
- Fuel Pumps: Redundant pumps for Level 1 systems
- Filters: Primary and secondary filtration
- Water Separators: Remove moisture from fuel
- Fill Connections: Accessible for emergency refueling
- Fuel Polishing: Recommended for long-term storage
- Natural Gas: Dual fuel connections where available
Testing & Maintenance Requirements
| Test Type | Level 1 Frequency | Duration | Load Requirements |
|---|---|---|---|
| No-Load Test | Weekly | 5-10 minutes | None |
| Monthly Test | Monthly | 30 minutes | Available load |
| Annual Test | Annual | 4 hours | 100% nameplate |
| Triennial Test | 36 months | 4 hours | With load bank |
| Transfer Test | Monthly | Complete cycle | Actual loads |
Maintenance Requirements
- Weekly Inspection: Visual check of all systems
- Oil & Filter Changes: Per manufacturer or oil analysis
- Coolant System: Annual flush and refill
- Battery Maintenance: Monthly specific gravity tests
- Fuel Testing: Annual quality testing
- Documentation: Written logs of all tests and maintenance
Installation Requirements
Location & Environment
- Indoor Installation: Separate room with proper ventilation
- Fire Rating: 2-hour separation for Level 1 systems
- Temperature: Maintain minimum 40°F (Level 1), 32°F (Level 2)
- Ventilation: Combustion air and cooling requirements
- Working Space: 3 feet minimum around equipment
- Outdoor Installation: Weather enclosures meeting Type ratings
Electrical Installation
- Separate feeders for emergency loads
- Proper grounding and bonding systems
- Surge protection devices
- Selective coordination of overcurrent devices
- Remote annunciator in attended location
- Integration with building management systems
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