What is Load Bank Testing? Generator Verification
Load bank testing is the process of running a backup generator under a simulated electrical load to verify it can produce its rated power output. A load bank is essentially a large resistor that converts the generator's electrical output into heat, allowing technicians to test the generator at 25%, 50%, 75%, and 100% of capacity without connecting to actual building loads.
How It Relates to Fuel Delivery
Backup generators that run only during brief monthly tests or occasional outages develop problems from underloading — wet stacking (unburned fuel accumulating in the exhaust system), carbon buildup, glazed cylinder liners, and degraded seals. Load bank testing at full rated capacity burns off these deposits and verifies the generator can actually deliver when needed.
A typical load bank test runs the generator at progressive loads — 25% for 30 minutes, 50% for 30 minutes, 75% for 30 minutes, and 100% for 2+ hours. During this time, the generator will consume significant fuel. A 500kW generator at full load burns approximately 35 gallons per hour, meaning a 4-hour test requires 140+ gallons of diesel.
NFPA 110 requires annual load bank testing for Level 1 (life safety) and Level 2 (critical operations) standby power systems. Many insurance policies and building codes also mandate it. BettyJet can deliver the fuel needed for scheduled load bank tests so your tank is full before testing begins.
Why It Matters for BettyJet Customers
Load bank testing burns a lot of diesel — plan ahead. BettyJet can deliver fuel before your scheduled test and top off your tank afterward, ensuring your generator is always ready for the real thing.
Frequently Asked Questions
How much fuel does a load bank test use?
It depends on generator size and test duration. A 500kW generator at full load burns about 35 gallons/hour. A typical 4-hour test requires 140+ gallons. BettyJet can deliver fuel specifically for your scheduled load bank test.
How often should generators be load bank tested?
NFPA 110 requires annual testing at full rated load for critical standby generators. Many facilities test quarterly or semi-annually. If your generator only runs during brief monthly tests, it especially needs regular load bank testing to prevent wet stacking.
Related Terms
ULSD stands for Ultra-Low Sulfur Diesel — a cleaner-burning diesel fuel containing no more than 15 parts per million (ppm) of sulfur. Since 2006, the EPA has required all on-road diesel sold in the United States to meet the ULSD standard, replacing Low Sulfur Diesel (LSD) which contained up to 500 ppm of sulfur.
Dyed DieselDyed diesel — also called red diesel or off-road diesel — is standard ULSD fuel that has been dyed red to indicate it is exempt from federal and state road taxes. It is chemically identical to on-road diesel but costs significantly less because the tax (typically $0.40-0.60/gallon) is not applied.
Wet HosingWet hosing is the practice of fueling vehicles or equipment directly from a mobile fuel truck rather than from a stationary storage tank. The fuel truck pulls up to each vehicle and fills it on-site — no bulk tank, no pump, no infrastructure required.
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