The National Fire Protection Association (NFPA) establishes safety standards that protect commercial building occupants against various dangers, one of which is improperly lit egress paths during low visibility. Besides requiring luminescent egress markings and safety signage to be placed along egress paths, the NFPA also requires regular testing of emergency generators. Combined, these measures help to ensure that (a) generator powered backup lighting will operate as expected, and (b) luminescent markings and signage will illuminate egress paths if backup lighting fails. Requirements for generator testing are contained in NFPA 110. If your building contains an emergency generator, practicing these requirements is a key to maintaining its reliability. Below are the monthly and annual testing requirements for diesel generators according to NFPA 110:
Monthly Testing (Sec. 8.4.2)
A monthly test is performed on Level 1 and Level 2 generators. A Level 1 generator is one whose failure could result in death or serious injury. A level 2 generator is one whose failure would not result in life-threatening injury. During testing, a generator should operate under available load for a minimum of thirty minutes. A successful test is one in which the generator:
• Achieves the minimum exhaust gas temperature for monthly testing as indicated by the owners manual, or
• Operates at normal temperature while running at no less than 30% of the nameplate Kilowatt rating.
If a generator cannot operate until its water and oil pressures have stabilized, it should be tested for less than thirty minutes to avoid prolonging its down time.
Yearly Testing (Sec. 18.104.22.168)
If a generator fails the monthly test, it should be operated under a load supplied by a load bank (i.e. load bank testing) for two continuous hours each year. During this two-hour period, the unit should be operated as follows:
• At 25% of the nameplate Kilowatt rating for 30 minutes.
• At 50% of the nameplate Kilowatt rating for 30 minutes.
• At 75% of the nameplate Kilowatt rating for 60 minutes.
The "exercise" supplied by load bank testing can improve a generator's operating capacity, making it more responsive during a real power outage.