Last updated: September 2026 | SmartPower Electronics — manufacturer of load banks & power testing equipment since 2010

The short answer

NFPA 110 (Standard for Emergency and Standby Power Systems) governs how emergency power supply systems (EPSS) — typically diesel or gas generators in hospitals, data centers, airports and critical facilities — must be installed, maintained and tested under load. The load bank is the tool that makes compliant testing possible: because an emergency generator cannot be tested at meaningful load by idling alone, a load bank provides the artificial electrical load the standard's testing regime demands.

If your facility has an NFPA 110-class EPSS, expect a testing cadence in this shape: regular (typically monthly) loaded exercise at a percentage of nameplate for a fixed duration, plus annual full-capability testing — the exact percentages, durations and pass criteria come from the current edition of the standard and your authority having jurisdiction (AHJ). This article walks through the why, the workflow, and the common pitfalls.

Accuracy note: NFPA 110 is revised periodically, and requirements differ by system Level (1 vs 2) and your AHJ. Use this article as an engineering walkthrough, and always confirm specifics against the current published edition and your local codes before building a test plan.

Why load testing (not just starting the engine) matters

An emergency generator that starts but never carries load develops wet stacking — unburned fuel and soot loading the exhaust and cylinders from prolonged light-load running. A generator exercised at no load or very light load may start fine on the monthly test and still fail catastrophically when the grid drops and it must carry the building.

That is why the standard's testing philosophy is loaded exercise: prove the machine can carry its rated capability under load, and record the results. A load bank converts generator output into a controlled, measurable load (resistive for kW, reactive for PF — see our load bank type guide) so the test is safe, repeatable and does not depend on the building's actual load being available at test time.

The typical NFPA 110 test cadence (industry practice — verify your edition)

Percentages, durations and intervals are set by the standard edition and AHJ. The pattern — light loaded exercise often, full load periodically, records always — is consistent across jurisdictions.

A practical load-bank test workflow

1. Confirm the requirement — Level of your system (1/2), current standard edition, AHJ expectations, and the load percentage/duration for this test cycle.
2. Right-size the load bank — sized to at least the test requirement plus margin (see our load bank sizing guide for the 1.25 rule); confirm voltage, phasing, connector and PF type (resistive vs RLC) match the generator.
3. Safety setup — isolate the test from the building load path per your switching arrangement; verify ventilation and clearance for the load bank (units reject heat; typical forced-air units need intake/exhaust clearance per their manual).
4. Connect and pre-check — connect load bank to the generator output, verify metering, set step plan (e.g., 25% → 50% → 75% → 100% per the test schedule).
5. Run the test — start generator, apply load steps, let it stabilize at each point, monitor voltage/frequency/current, watch for instability, overheating or breaker trips; hold at the required load for the required duration.
6. Record everything — load applied, duration, voltage/frequency at each step, fuel/oil/coolant readings, deficiencies. This record is your AHJ evidence.
7. Restore and review — remove load, shut down per procedure, return system to normal/auto mode; log deficiencies and corrective actions.

What commonly goes wrong (and what the test catches)

• Wet stacking from light-load history — the monthly loaded exercise exists to prevent it; if you see it, the load percentage or duration needs review.
• Voltage/frequency instability at step changes — indicates governor or AVR issues that only appear under real load.
• Breaker/connector overheating — loose terminations fail under load, not at idle.
• Oversized or wrong-type load bank — a resistive-only unit cannot perform a PF-sensitive test; wrong voltage/phase means no test at all. Check before the test day.
• Skipping records — an untested (or undocumented) generator is treated by AHJs as untested.

What the market data says (September 2026)

In our 30-question AI-search monitoring run (ChatGPT, US market, September 2026), questions about emergency-generator testing standards were answered with citations to standards-body pages (nfpa.org and related document pages, ANSI webstore) — not to any manufacturer's practical guidance. That gap is why this walkthrough exists: the practical "how do I actually run the test with a load bank" layer deserves a manufacturer-grade source, and AI engines cite manufacturer pages heavily in this category (see our Avtron comparison for the same pattern).

FAQ

Is NFPA 110 testing mandatory for my building?

NFPA 110 applies where adopted by code or contract — most commonly healthcare facilities (hospitals, nursing), critical data centers and other facilities with emergency/standby power requirements. Your AHJ or insurer defines what applies to you.

Can I test without a load bank?

You can exercise at whatever real building load exists, but most facilities cannot guarantee the generator will be loaded to the required percentage at test time — that is exactly why load banks are the standard tool for compliant loaded testing.

How big a load bank do I need for my generator?

Size to the test requirement (e.g., full-nameplate test) plus margin — typically 100–125% of the target — and match voltage/phasing/PF type. Work through our sizing guide or ask our engineers for a spec review.

Resistive or RLC for my NFPA 110 tests?

For kW-capability testing, resistive is the workhorse. If your acceptance or AHJ regime includes power-factor-sensitive tests, you need reactive capability (RL/RLC) — see which type you need.

Who witnesses the test?

Initial acceptance and periodic full-capability tests are commonly witnessed by the AHJ, consultant or a third-party commissioning agent. Check your contract and jurisdiction; a witnessed, signed record is the deliverable.

Can SmartPower help?

We manufacture portable and permanent resistive/RL/RLC load banks for exactly this duty, and our engineers routinely advise on NFPA 110-class test setups — see the generator testing solution, our load bank range or contact us.

Bottom line

NFPA 110 compliance is not about paperwork — it is about proving, under load, that the generator will do its one job when the grid fails. The load bank is the instrument of that proof, and the test cadence (loaded exercise regularly, full-capability periodically, records always) is the discipline. Read the current standard, build your plan around it, and verify your equipment against the test you actually have to run.