What is Load Bank Testing?
A Load Bank is a piece of equipment used to simulate the actual electrical load that the generator is designed to power. A Load Bank tests the generator engine’s ability to perform and provide the required horsepower needed during a power outage. A Load Bank Test will also prove other components of the generator are working properly, such as the voltage regulator, governor, generator exciter, cooling system, etc.
Most facilities are required to perform load bank testing in order to comply with NFPA guidelines. Load bank testing not only helps in meeting code requirements, but is also a critical part to help ensure that the Emergency Power System (EPS) will be ready when needed in an emergency.
Benefits of Load Bank Testing
Even if your facility is not required to follow NFPA guidelines, the use of Load Bank Testing also plays an essential role in any preventive maintenance program.
While a Building Load Test (Transfer Test) is done to verify complete operation of the Emergency Power System (generator and automatic transfer switch) with actual building loads, it may not help identify any issues with the generator itself if building load is very low.
Load Bank Testing can load the generator up to 100% of its rated capacity. Generators that are regularly ran with little or no load at all become unreliable and costly to repair due to fuel system problems, lubricating oil deterioration, carbon build up, and wet stacking. Wet stacking is the accumulation of unburned oil residue in the exhaust system, which is a fire hazard. Wet stacking may also cause oil leaks at the engine itself.
Load Bank Testing on a regular basis will help prevent wet stacking as well as cleaning the engine by removing carbon build up. Load Bank Testing also helps detect if the generator will perform properly under extreme stress and ensure that it will perform properly in the event of an emergency.
NFPA 110 (2016 edition) states in part:
Chapter 8: Routine Maintenance and Operational Testing
*8.4 Operational Inspection and Testing
*8.4.2 Diesel generator sets in service shall be exercised at least once monthly, for a minimum of 30 minutes, using one of the following methods:
(1) Loading that maintains the minimum exhaust gas temperatures as recommended by the manufacturer.
(2) Under operating temperature conditions and at not less than 30 percent of the EPS standby nameplate rating.
*188.8.131.52 Diesel-powered EPS installations that do not meet the requirements of 8.4.2 shall be exercised monthly with the available EPS load and shall be exercised annually with supplemental loads at not less than 50 percent of the EPS nameplate kw rating for 30 continuous minutes and not less than 75 percent of the EPS nameplate kw rating for 1 continuous hour for a total of not less than 1.5 continuous hours.