NFPA 110 Weekly Exercise and Monthly Load Logging for Commercial Standby
Why this matters
NFPA 110 Standard for Emergency and Standby Power Systems is the document the Authority Having Jurisdiction (AHJ) holds the property owner against during a fire-marshal inspection of a Level 1 or Level 2 Emergency Power Supply System (EPSS). The standard requires weekly inspection, a monthly operational test under load, an annual supplemental-load exercise for diesel units that cannot make the monthly load floor on building load alone, and a longer full-duration test on a 36-month cycle, with records kept on site for the life of the system. Most commercial generator service contracts include the weekly walkdown and monthly load test; the technician's signed log is what the inspector reviews. Missing or incomplete logs is the most common Level 1 EPSS finding in the field.
Scope and the two levels
- Level 1: failure of the EPSS could result in loss of human life or serious injury. Hospitals, dialysis centers, large assembly occupancies under NFPA 101. Highest test frequency and documentation rigor.
- Level 2: failure is less critical but still important. Some sewage lift stations, communications facilities. Same weekly and monthly test cadence, more tolerance on maintenance and repair timing than Level 1 gets.
- Do not confuse Level with Class or Type, because inspectors do not. Level is the consequence of failure, 1 or 2. Type is the maximum seconds the load may be without acceptable power, so a Type 10 system must be carrying load within 10 seconds. Class is the minimum hours the EPS runs at rated load without refueling, so Class 48 is a two-day fuel supply. A life-safety branch is typically Level 1, Type 10, and whatever Class the occupancy and the AHJ demand.
- Health-care occupancies also fall under NFPA 99 and the CMS Conditions of Participation, which layer their own testing and documentation on top. This article covers the NFPA 110 baseline.
Weekly inspection items (NFPA 110 Chapter 8)
A trained operator (the building engineer or the contracted service tech under a written service agreement) performs the weekly inspection. Visual only, generator not started by the inspection itself unless that is the monthly test day.
- Engine fluid levels: oil, coolant, fuel. Mark dipstick reading and coolant surge tank level. Record any addition.
- Battery voltage at terminals with a calibrated DMM, not the panel display. Battery electrolyte level on wet-cell units.
- Battery charger output current and float voltage.
- Block heater operation: jacket-water temperature above the setpoint (typically 90 F or per OEM). Probe the upper coolant hose by hand; warm is correct, ambient is a failed heater.
- Fuel level in the day tank or main tank. Indoor fuel storage clearances, containment and venting are governed separately by NFPA 37 and NFPA 30; check the aggregate indoor capacity limit in the edition your AHJ enforces rather than working from memory.
- Air intake louvers and radiator discharge louvers free of obstruction; rodent screens intact.
- Belt condition (deflection per OEM), no fluid leaks under the unit, no exhaust soot streaking.
- ATS position indicator confirms Normal source; no nuisance alarms on the genset annunciator or the remote annunciator in the building.
- Sign and date the bound log. Note any deficiency by item number; an open finding from last week must close before the next entry.
Monthly load test (NFPA 110 Section 8.4.2)
Run the generator monthly with the building load (or a connected load bank) to confirm the unit produces nameplate power and the ATS transfers cleanly.
- Notify building occupants and the AHJ-listed contact list per the site's emergency plan. Critical-care facilities require additional coordination.
- Verify ATS is in Auto. Initiate a test transfer via the ATS test switch (preferred) or by simulating a utility outage at the test source.
- Confirm the engine cranks and picks up load inside the system's Type rating. Type 10 is the common life-safety figure and means the load terminals are back on acceptable power within 10 seconds of losing the normal source. Time it with a stopwatch, not by feel.
- Hold load for a minimum of 30 minutes. The monthly exercise in NFPA 110 Section 8.4.2 is satisfied either by loading that holds the exhaust gas temperature the engine manufacturer calls for, or by running at not less than 30 percent of EPS nameplate kW. The point of both options is the same: keep the cylinders hot enough that unburned fuel is not laying down in the exhaust. Building load alone often fails this floor in mild months; supplement with a load bank.
- During the run, log every 15 minutes: oil pressure, coolant temperature, battery voltage with engine running, fuel pressure, exhaust temperature if instrumented, kW, kVAR, power factor, line-to-line voltage on all three phases, frequency.
- After the run, retransfer to Normal, observe cooldown timer per OEM, confirm the unit returns to Ready/Auto with no alarms.
- Visual walkdown for new leaks, loose hardware, exhaust manifold streaking.
Annual supplemental load test, and the 36-month test
These are two different tests on two different clocks, and they get conflated constantly. Keep them straight in the log.
Annual supplemental load test (NFPA 110 Section 8.4.2). This one applies to a diesel installation that cannot make the monthly exercise requirement on available building load. Those units run monthly on whatever load the building gives them, and then once a year get a supplemental (load bank) exercise stepped through the nameplate rating:
- 25 percent of nameplate for 30 minutes
- then 50 percent of nameplate for 30 minutes
- then 75 percent of nameplate for 60 minutes
Two continuous hours total, in that ascending order, without shutting down between steps. Note that the top step is 75 percent, not 100. Nobody is asking you to hold the unit at full nameplate for this test.
36-month test (NFPA 110 Section 8.4.9). Level 1 EPSS gets tested once in every 36 months for the duration of its Class, or 4 hours, whichever is less, at not less than 30 percent of nameplate. This is the one people misremember as an annual four-hour run. It is triennial.
Both are typically load-bank visits. Document the load bank's calibration, and log which test you actually performed against which section, because an inspector reading "4 hour annual" in a logbook will ask you to produce a section that says so and there is not one.
Recordkeeping that survives an inspection
- Bound logbook stored at the generator or in the engineering office, available 24/7. Many AHJs accept a hybrid: paper log on the wall plus a digital backup. The paper log is the one the inspector pulls.
- Each entry: date, time, technician printed name + signature, ambient temperature, observations by checklist item, deficiencies, work orders opened.
- Retain records for the life of the equipment.
- A real outage counts toward the monthly test only if the load and the duration actually met Section 8.4.2. Log the kW and the run time and let the numbers decide; if they fall short, document the outage separately and still run the test.
A generator that runs every week at no-load or below 30 percent for years develops wet-stacking, fuel-diluted oil, and glazed cylinder bores. The owner often blames the service contractor when a real outage produces black smoke and a derate. Document every month whether load reached the 30 percent floor and, if not, recommend a load-bank visit in writing. The recommendation in the log shifts liability.
References
- NFPA 110 Standard for Emergency and Standby Power Systems, current edition.
- NFPA 99 Health Care Facilities Code, Chapter 6 Electrical Systems.
- NFPA 37 Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines.
- Generac Industrial Power 50-300 kW Standby Owner's Manual, scheduled maintenance section.
- Kohler KD Series Operation and Maintenance Manual, periodic service intervals.