NFPA 110 Load Bank Testing: What Changed and Why

Most industrial standby generators spend nearly all their operating life doing almost nothing. They run a brief monthly exercise cycle, then sit idle again until the next test or the next real outage. That pattern feels harmless, but it's exactly what causes generators to fail when a facility actually needs them.

Load bank testing exists to catch that failure mode before it happens. NFPA 110, the standard that governs emergency and standby power systems, also recently updated how that testing is performed. If your facility hasn't looked at its testing program in a while, it's worth understanding what the standard actually requires and how the current protocol differs from older guidance still floating around online.

Why Monthly Generator Exercise Isn't Enough

NFPA 110 requires monthly operational testing for Level 1 and Level 2 emergency power supply systems (EPSS). The generator has to run under load for at least 30 minutes, carrying a minimum of 30% of its nameplate kW rating.

The problem is that most facilities' actual connected load during a routine test rarely reaches that threshold. When a diesel generator runs consistently under 30% load, it develops a condition called wet stacking: unburned fuel and carbon accumulate in the exhaust system, turbocharger, and cylinder walls. Left unaddressed, that buildup leads to fouled injectors, glazed cylinder liners, and a generator that looks fine on paper but underperforms exactly when it's called on to run at full output.

If a monthly test can't reach that 30% threshold and exhaust temperatures don't confirm adequate combustion, NFPA 110 requires a supplemental load bank test using a portable or stationary load bank device rather than the building's actual connected load.

What Changed in the Current Testing Protocol

Older guidance on annual load bank testing describes a three-step process: 25% of nameplate load for 30 minutes, 50% for 30 minutes, then 75% for 60 minutes, for roughly two hours total. That sequence is still widely referenced, but the current edition of NFPA 110 has moved to a simplified two-step protocol: 50% of nameplate load for 30 minutes, followed by 75% for a full hour. The 25% warm-up step has been dropped, putting more of the test time at sustained medium-to-high load, which does more to burn off existing carbon deposits and validate cooling system performance under real stress.

Because code adoption isn't uniform, which protocol applies to your facility depends on which edition of NFPA 110 your local authority having jurisdiction (AHJ) has adopted. It's worth confirming that directly rather than assuming, especially if your facility's last load bank test predates this change.

Separately, Level 1 EPSS installations require a triennial test every 36 months: a continuous run for the full duration of the system's assigned class, up to a maximum of 4 continuous hours if the class duration is longer than that.

A Safety Requirement That's Easy to Miss

One NFPA 110 requirement gets overlooked more often than it should: the load bank has to be wired so it automatically disconnects and is replaced by the facility's actual essential load if utility power fails during the test. Manually switching over doesn't satisfy this requirement. If a real outage happens mid-test and the transfer isn't automatic, the facility's actual critical loads are left unprotected at the exact moment they need power most. This is a wiring and controls detail, not just a testing procedure, and it's worth verifying as part of any EPSS design or retrofit.

Documentation Matters As Much As the Test Itself

A generator that performs perfectly during testing but has incomplete records is still a compliance gap. NFPA 110 documentation should include the test date, technician name, generator identification, test duration, load levels reached at each stage, and any anomalies or corrective actions. Facilities are far more likely to run into problems from missing or vague records than from an actual equipment failure, so a testing log that captures real data instead of a simple pass/fail note is worth the extra few minutes it takes to complete.

How HRE Can Help

Load bank testing itself is typically performed by a generator service provider, but the electrical infrastructure around your emergency power system determines whether that testing program actually protects your facility. HRE Construction designs and installs industrial standby power systems built around how a facility actually operates, including correct load classification under NEC Article 700, 701, or 702, properly sized and wired transfer equipment, and the automatic transfer controls that keep a load bank test from becoming a liability if utility power drops mid-test. We also support the ongoing testing, commissioning, and documentation that keeps an EPSS ready when it's actually needed, not just on paper.

If it's been a while since your facility's standby power system was evaluated against current NFPA 110 requirements, contact HRE Construction to talk through what your system needs.

Frequently Asked Questions

How often does NFPA 110 require load bank testing?

Load bank testing is required when a generator's monthly exercise test doesn't reach 30% of its nameplate kW rating and exhaust temperatures don't confirm adequate combustion. In practice, many facilities schedule an annual load bank test as a standard part of their maintenance program rather than waiting to see if the monthly test falls short.

What's the difference between the monthly test and the annual load bank test?

The monthly test runs the generator under whatever load the building's connected circuits provide, for at least 30 minutes at a minimum of 30% nameplate kW. The annual load bank test uses a dedicated load bank device to apply a controlled, higher load, currently 50% of nameplate for 30 minutes followed by 75% for an hour under the current NFPA 110 edition, specifically to counteract the effects of chronic light loading.

Does load bank testing apply to industrial facilities, or just hospitals and data centers?

NFPA 110 applies to any facility with a Level 1 or Level 2 emergency power supply system, which includes many industrial and manufacturing facilities running standby power for life safety systems or continuous processes, not just healthcare or data center environments.